CN113355325B - Preparation method and application of humanized ACE2 gene modified mouse embryonic stem cell model - Google Patents

Abstract

The invention relates to the field of biological medicine, in particular to a preparation method and application of a humanized ACE2 gene modified mouse embryonic stem cell model. The invention provides a sgRNA fragment sequence. The targeting vector containing the sgRNA fragment sequence can specifically target ACE2 genes and can be used for preparing humanized ACE2 gene modified mouse embryonic stem cell models. The sgRNA fragment sequence of the invention has better targeting specificity and efficiency of cutting target genes.

Description

Preparation method and application of humanized ACE2 gene-modified mouse embryonic stem cell model

Technical Field

The present invention relates to the field of biomedicine, and in particular to a method for preparing a humanized ACE2 gene-modified mouse embryonic stem cell model and application thereof.

Background Art

Although 2019-nCoV has been infected in cell models such as Vero E6 cells for drug screening, the singleness of cell models is far from comparable to the advantages of animal models.

Experimental animal disease models are indispensable research tools for studying the causes and pathogenesis of human diseases, and developing prevention and treatment technologies and therapeutic drugs. Common experimental animals include mice, rats, guinea pigs, hamsters, rabbits, dogs, monkeys, pigs, and fish. However, there are still many differences in the gene and protein sequences between humans and animals. Many human proteins cannot bind to homologous proteins in animals to produce biological activity, resulting in the results of many clinical trials not being consistent with the results of animal experiments.

With the continuous development and maturity of genetic engineering technology, human cells or genes are used to replace or displace the endogenous cells or genes of animals to establish a biological system or disease model closer to humans, and to establish a humanized experimental animal model (humanized animal model1), which has provided an important tool for new clinical treatment methods or means. Among them, the gene humanized animal model, that is, using gene genetic manipulation technology, replaces the same gene of animals with normal or mutant genes of humans, and can establish a normal or mutant system closer to humans in the animal body. Because the humanized animal itself not only has important application value, such as through gene humanization, it can also improve and enhance the cell humanized mouse CN107815468 A2/28 page model, more importantly, due to the presence of human gene fragments, the animal body can express or partially express proteins containing human functions, thereby greatly reducing the clinical experimental differences between humans and animals, and providing the possibility for drug screening at the animal level.

Like SARS coronavirus, 2019-nCoV uses angiotensin-converting enzyme 2 (ACE2) as a key target for infecting humans. In addition to infecting humans, 2019-nCoV can also infect a variety of mammals such as monkeys, pigs, rabbits, ferrets, and gorillas, but mice and rats are excluded. Monkeys, pigs, and rabbits are used as animal models to infect 2019-nCoV for drug screening, but their growth cycle is long and their body size is large, making it difficult to operate in large quantities. However, the mouse model, which is relatively easy to operate in large quantities, is not susceptible to 2019-nCoV.

Summary of the invention

Because there are certain differences in the gene sequences of human ACE2 and mouse ACE2, there are literature reports that after virus infection, human ACE2 is more sensitive to SARS-CoV than mouse ACE2, and the pathological symptoms are more obvious. Current clinical research urgently needs better animal models.

It has been confirmed that hACE2 transgenic mice can be infected with 2019-nCoV and show typical pathogenic characteristics in lung tissue (https://www.biorxiv.org/content/10.1101/2020.02.07.939389v3#disqus_thread). However, hACE2 transgenic mice are systemic hACE2 overexpression mouse models and cannot simulate the spatiotemporal tissue expression characteristics of ACE2. The humanized ACE2 mouse model of the present invention is an original mouse Ace2 site-specific hACE2 mouse model, which can simulate the original mACE2 expression characteristics, has tissue specificity, and more rigorously simulates the pathogenesis of human infection with 2019-nCoV.

Therefore, the present invention will prepare a 2019-nCoV susceptible mouse humanized ACE2 animal model in large quantities by expressing humanized ACE2 at the mouse Ace2 site for drug screening and disease research on 2019-nCoV.

One of the purposes of the present invention is to provide a specific nucleic acid fragment sequence.

Another object of the present invention is to provide a sgRNA sequence that specifically targets the ACE2 gene.

Another object of the present invention is to provide a targeting vector that specifically targets the ACE2 gene.

Another object of the present invention is to provide an ACE2 gene humanized cell line.

Another object of the present invention is to provide a method for constructing an ACE2 gene humanized cell line.

Another object of the present invention is to provide an ACE2 gene humanized cell line.

Another object of the present invention is to provide a method for constructing a genetically humanized animal.

Another object of the present invention is to provide a humanized ACE2 gene-modified mouse embryonic stem cell model.

In one aspect, the present invention provides a nucleic acid fragment sequence, and the nucleic acid fragment sequence is shown in SEQ ID NO: 1 or SEQ ID NO: 2. The nucleic acid fragment sequence disclosed in the present invention has good targeting specificity and efficiency in cutting target genes.

In some embodiments, the upstream and downstream primer sequences of the nucleic acid synthesized as SEQ ID NO: 1 are shown as SEQ ID NO: 6 and SEQ ID NO: 7, respectively. In some embodiments, the upstream and downstream primer sequences of the nucleic acid synthesized as SEQ ID NO: 2 are shown as SEQ ID NO: 4 and SEQ ID NO: 5, respectively.

In some embodiments, the nucleic acid is sgRNA.

In some embodiments, the gene targeted by the sgRNA fragment sequence is the animal ACE2 gene, which is used for site-specific cutting of the ACE2 gene.

In some embodiments, the sgRNA fragment sequence is used to construct a humanized animal model.

In some embodiments, the cutting point of the sgRNA fragment sequence is located in exon 1 of the animal ACE2 gene.

In some embodiments, the cleavage point target is within the 140bp base range after the 5'UTR of the animal ACE2 gene.

In some embodiments, the animal is a mammal.

In some embodiments, the mammal is a rodent.

In some embodiments, the rodent is a mouse.

On the other hand, the present invention provides a targeting vector comprising a 5' homology arm, a human ACE2 gene fragment and a 3' homology arm; the targeting vector targets an animal ACE2 gene, and the animal ACE2 gene contains a cleavage point corresponding to the sgRNA fragment sequence of claim 1 or 2. The 5' homology arm is a 5' homology arm homologous to the 5' target sequence at the target genomic locus.

In some embodiments, the targeting vector is used to insert the CDS sequence of the human ACE2 gene into the promoter and 5'UTR region sequence of the animal gene, and then use the animal target gene promoter to initiate the expression of the human target gene.

In some embodiments, the targeting vector further comprises a 3' homology arm, wherein the 3' homology arm is a 3' homology arm homologous to the 3' target sequence at the target genomic locus.

In some embodiments, the 5' homology arm sequence is shown as SEQ ID NO:13, and the 3' homology arm sequence is shown as SEQ ID NO:14.

In some embodiments, the CDS sequence of the ACE2 gene is shown in SEQ ID NO:10.

In some embodiments, the targeting vector further comprises an SV40 polyA sequence as shown in SEQ ID NO: 12, and the SV40 polyA sequence is located after the CDS sequence.

In some embodiments, the targeting vector further comprises a selection marker PGK-Puro.

In some embodiments, the animal is a mammal.

In some embodiments, the animal is a mouse.

In some embodiments, the targeting vector further comprises a pX330 vector.

On the other hand, the present invention provides a DNA molecule encoding the sgRNA fragment sequence.

On the other hand, the present invention provides a cell comprising the sgRNA fragment sequence or the targeting vector or the DNA molecule.

On the other hand, the present invention provides the use of the sgRNA fragment sequence in preparing a genetic humanized cell line or a humanized animal model.

In some embodiments, the gene is ACE2.

In some embodiments, the animal is a mammal.

In some embodiments, the animal is a rodent.

In some embodiments, the animal is a mouse.

On the other hand, the present invention provides a method for constructing a humanized animal cell line, wherein the sgRNA fragment sequence is used.

In some embodiments, the method includes introducing a human target gene into an animal cell, so that the target gene expresses the CDS of the human full-length target gene in situ in the animal cell.

In some embodiments, the target gene is ACE2.

In some embodiments, the animal is a mammal.

In some embodiments, the animal is a rodent.

In some embodiments, the animal is a mouse.

In some embodiments, the cells are embryonic stem cells.

In some embodiments, the method uses gene editing technology to construct a humanized animal cell model.

In some embodiments, the gene editing technology includes DNA homologous recombination technology based on embryonic stem cells and CRISPR/Cas9 technology.

In some embodiments, the gene editing technology is based on CRISPR/Cas9 gene editing technology to construct ACE2 humanized animals.

In some embodiments, the construction method comprises the following steps: (1) constructing the targeting vector of claim 3; (2) introducing the constructed targeting vector and the vector connected with sgRNA into embryonic stem cells of animal origin; (3) culturing the embryonic stem cells in step (2) into clones.

In some embodiments, the animal is a mammal.

In some embodiments, the mammal is a rodent.

In some embodiments, the rodent is a mouse.

On the other hand, the present invention provides an ACE2 gene humanized cell line prepared by the method described.

In some embodiments, the cell line is a humanized mouse embryonic stem cell, which can express the full-length human ACE2 protein after specific differentiation or preparation into a mouse model, while the expression of endogenous ACE2 protein is reduced or disappears.

On the other hand, the present invention provides a method for constructing a genetically humanized animal model, comprising injecting the animal cells into an animal.

In some embodiments, the method for constructing the genetically humanized animal model includes forming animal individuals by tetraploid compensation or blastocyst injection of the animal cells.

On the other hand, the present invention provides a humanized mouse or its offspring's tissue, body fluid, cell, and their fragments or extracts, wherein the humanized mouse is obtained by using the method for constructing a genetic humanized animal model.

Humanized ACE2 gene-modified mice were successfully obtained using the method of the present invention.

In some embodiments, the humanized ACE2 genetically modified mouse expresses human ACE2 at the RNA level and has tissue specificity.

In some embodiments, the humanized ACE2 genetically modified mouse expresses human ACE2 at the protein level and has tissue specificity.

In some embodiments, the present invention shows that the humanized ACE2 gene-modified mice obtained by the method of the present invention are susceptible to SARS-CoV-2. Thus, mice susceptible to 2019-nCoV are successfully obtained, which can provide a good animal model for drug screening or other research on 2019-nCoV. It has great practical significance.

In still another aspect, the present invention provides the use of a humanized animal model or its progeny obtained by the construction method in the manufacture of human antibodies, or as a model system for pharmacology, immunology, microbiology and medical research, or in the production and use of animal experimental disease models for etiology research and/or for the development of new diagnostic strategies and/or treatment strategies, or in the screening, verification, evaluation or research of ACE2 gene function, ACE2 antibodies, drugs targeting ACE2 targets, and efficacy research.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a plasmid map of pX330.

Figure 2 shows the sequencing results of pX330-sgRNA1 construction.

Figure 3 shows the sequencing results of pX330-sgRNA2 construction.

FIG4 is the result of verifying the cutting efficiency of pX330-sgRNA1-3.

Figure 5 is a diagram showing the sequencing results of pX330-sgRNA3 construction.

Figure 6 is a schematic diagram of the humanized ACE2 targeting strategy.

Figure 7 shows the sequencing results of the humanized ACE2 targeting vector.

FIG8 is a PCR identification diagram of the three-fragment connection in Comparative Example 1.

FIG. 9 is a diagram showing the PCR identification results of the genotype of humanized ACE2 mouse embryonic stem cells.

Figure 10 is a graph showing the PCR identification results of the humanized ACE2 mouse embryonic stem cell genotype after deleting PGK-Puro.

Figure 11 is a schematic diagram of the humanized ACE2 gene.

FIG. 12 shows the humanized ACE2 gene-modified mice obtained by the present invention.

Figure 13 shows that humanized ACE2 gene-modified mice express human ACE2 at the RNA level and have tissue specificity.

The tissue immunofluorescence results in Figure 14 show that human ACE2 protein is specifically expressed in the tissues of humanized ACE2 gene-modified mice.

Figure 15 shows that the humanized ACE2 gene-modified mice of the present invention are susceptible to SARS-CoV-2.

DETAILED DESCRIPTION

The technical solution of the present invention is further described below by specific embodiments, which do not limit the protection scope of the present invention. Some non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the protection scope of the present invention.

Unless otherwise defined, the definitions of all technical and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein can be applied to the methods of the present invention, and preferred methods and materials are described in the specific embodiments.

As used herein, "a" and "an" refer to the grammatical indefinite article, meaning "one", "a kind" or "a plurality", "a variety" (i.e., "at least one", "at least one"). For example, "an element" refers to one or a kind of element.

"CDS" is the abbreviation of coding sequence, which refers to any nucleotide sequence that encodes the polypeptide product of a gene. In contrast, the term "non-coding sequence" refers to any nucleotide sequence that does not encode the polypeptide product of a gene.

The term "fragment" will be understood to refer to a nucleotide sequence that is shorter than a reference nucleic acid and that comprises the same nucleotide sequence as the reference nucleic acid in the common portion. If appropriate, such nucleic acid fragment according to the present invention can be included in a larger polynucleotide, and this fragment is a constituent of this larger polynucleotide. Such a fragment comprises an oligonucleotide having a length of at least 6,8,9,10,12,15,18,20,21,22,23,24,25,30,39,40,42,45,48,50,51,54,57,60,63,66,70,75,78,80,90,100,105,120,135,150,200,300,500,720,900,1000 or 1500 continuous nucleotides of nucleic acid of the present invention, or alternatively consists of such an oligonucleotide.

In this specification, unless the context requires otherwise, the words "comprise" and "include" will be understood to mean including the steps or elements or a collection of steps and elements, but not excluding any other steps or elements or a collection of steps and elements; that is, an open limitation.

"Corresponding to" means: (a) a polynucleotide has a nucleotide sequence that is substantially identical or complementary to all or part of a reference nucleotide sequence, or a polynucleotide encodes an amino acid sequence that is completely identical to the amino acid sequence in a peptide or protein; or (b) a peptide or polypeptide has an amino acid sequence that is substantially identical to the amino acid sequence in a reference peptide or protein.

The term "downstream" refers to a nucleotide sequence located at the 3' end of a reference nucleotide sequence. In particular, a downstream nucleotide sequence generally refers to a sequence after the transcription start point. For example, the translation start codon of a gene is located downstream of the transcription start site.

The term "upstream" refers to a nucleotide sequence located at the 5' end of a reference nucleotide sequence. In particular, upstream nucleotides generally refer to sequences located at the 5' side of a coding sequence or transcription start site. For example, most promoters are located upstream of the transcription start site.

"Promoter" refers to a DNA sequence that can control the expression of a coding sequence or functional RNA. Generally speaking, the coding sequence is located at the 3' end of the promoter sequence. The promoter can be derived from a natural gene as a whole, or composed of different elements derived from different promoters found in nature, or even include synthetic DNA fragments. It should be understood by those skilled in the art that different promoters can direct genes to be expressed in different tissues or cell types, or at different stages of development, or in response to different environmental or physiological conditions. Promoters that cause genes to be expressed in most cell types at most times are generally referred to as "constitutive promoters". Promoters that cause genes to be expressed in specific cell types are generally referred to as "cell-specific promoters" or "tissue-specific promoters". Promoters that cause genes to be expressed at specific developmental or cell differentiation stages are generally referred to as "developmental specific promoters" or "cell differentiation specific promoters". After cells are exposed to agents, biomolecules, chemicals, ligands, light or the like that induce promoters, or cells are treated with these substances, promoters that are induced and cause genes to be expressed are generally referred to as "inducible promoters" or "regulatory promoters". It should also be recognized that because in most cases the exact boundaries of regulatory sequences have not been completely defined, DNA fragments of different lengths may have identical promoter activity.

The term "5'UTR" or "5' non-coding sequence" or "5' untranslated region (UTR)" refers to the DNA sequence located upstream (5') of a coding sequence.

The terms "restriction endonuclease" and "restriction enzyme" refer to enzymes that bind to and cleave specific nucleotide sequences within double-stranded DNA.

The term "vector" means a nucleic acid molecule that is capable of transferring a nucleic acid molecule to which it has been linked. One type of vector is a "plasmid," which refers to a circular double-stranded DNA loop into which additional DNA segments can be linked. Another type of vector is a viral vector, in which additional DNA segments can be linked into the viral genome. Certain vectors are capable of self-replication in a host cell into which they are introduced (e.g., bacterial vectors with bacterial origins of replication and episomal mammalian vectors). Other vectors (e.g., non-episomal mammalian vectors) are capable of integrating into the genome of a host cell upon introduction into the host cell, thereby replicating with the host genome. In addition, certain vectors are capable of directing the expression of genes to which they are operatively linked.

Some vectors referred to herein as "recombinant expression vectors" (or simply "expression vectors") refer to vectors, plasmids or vectors designed to allow the inserted nucleic acid sequence to be expressed after transformation into a host. In general, expression vectors used in recombinant DNA technology are often in the form of plasmids. "Plasmid" and "vector" are used interchangeably in this specification because plasmids are the most commonly used form of vectors. However, the present invention is intended to include other forms of such expression vectors, such as viral vectors (such as replication-defective retroviruses, adenoviruses and adeno-associated viruses), which serve the same role.

The term "plasmid" refers to an extrachromosomal element that often carries genes that are not part of the central metabolism of the cell and is often in the form of a circular double-stranded DNA molecule. Such an element can be an autonomously replicating sequence, a genome integrating sequence, a phage, or a nucleotide sequence from any source, linear, circular or supercoiled, single-stranded or double-stranded DNA or RNA, in which many nucleotide sequences have been linked or recombined into a unique structure that is capable of introducing a promoter fragment and DNA sequence for a selected gene product and appropriate 3' non-translated sequences into the cell.

"Targeting vector" or "targeting vector" is a DNA construct containing a sequence "homologous" to an endogenous chromosomal nucleic acid sequence adjacent to the desired genetic modification. The flanking homologous sequences (called "homology arms") guide the targeting vector to locate at a specific chromosomal position in the genome by means of the homology between the homology arms and the corresponding endogenous sequences, and introduce the desired genetic modification by a process called "homologous recombination." "Targeting vector" and "targeting vector" can be used interchangeably at some times. A targeting vector is used to introduce an insert nucleic acid into a target locus of a rat, eukaryotic, non-rat eukaryotic, mammal, non-human mammal, human, rodent, non-rat rodent, mouse or hamster nucleic acid. The targeting vector comprises the insert nucleic acid and further comprises a 5' homology arm and a 3' homology arm, which flanks the insert nucleic acid. The homology arms flanking the insert nucleic acid correspond to regions within the target locus of a rat, eukaryotic, non-rat eukaryotic, mammal, non-human mammal, human, rodent, non-rat rodent, mouse or hamster nucleic acid. For ease of reference, the corresponding homologous genomic region within the target genomic locus is referred to herein as a "target site". For example, a targeting vector may comprise a first insert nucleic acid flanked by a first homology arm complementary to the first target site and a second homology arm complementary to the first target site. Thus, the targeting vector thereby facilitates integration of the insert nucleic acid into the target locus of a rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster nucleic acid via a homologous recombination event occurring between the homology arms and the complementary target sites within the genome of the cell.

In one embodiment, the target locus of the rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster nucleic acid comprises a first nucleic acid sequence that is complementary to the 5' homology arm and a second nucleic acid sequence that is complementary to the 3' homology arm.

The vector can be introduced into the desired host cell by methods known in the art, such as transfection, electroporation, microinjection, transduction, cell fusion, DEAE dextran, calcium phosphate precipitation, lipofection (lysosome fusion), use of a gene gun or a DNA vector transporter (see, e.g., Wu et al., 1992, J. Biol. Chem. 267:963-967; Wu and Wu, 1988, J. Biol. Chem. 263:14621-14624; and Hartmut et al., Canadian Patent Application No. 2,012,311 filed March 15, 1990).

The term "transfection" refers to the uptake of exogenous or heterologous RNA or DNA by a cell. When exogenous or heterologous RNA or DNA has been introduced into a cell, the cell is "transfected" by such RNA or DNA. When the transfected RNA or DNA affects a phenotypic change, the cell is "transformed" by the exogenous or heterologous RNA or DNA. The transforming RNA or DNA can be integrated into (covalently linked into) the chromosomal DNA that makes up the genome of the cell.

The term "homology" or "homologous" refers to two sequences, such as nucleotide or amino acid sequences, that are optimally aligned and compared with at least about 75% of the nucleotides or amino acids, at least about 80% of the nucleotides or amino acids, at least about 90-95% of the nucleotides or amino acids, such as more than 97% of the nucleotides or amino acids being identical. Those skilled in the art will appreciate that for optimal gene targeting, the targeting construct should contain arms that are homologous to endogenous DNA sequences (i.e., "homology arms"); therefore, homologous recombination can occur between the targeting construct and the targeted endogenous sequence.

As used herein, homology arms and target sites (i.e., homologous genomic regions) are complementary to each other when two regions have a sufficient level of sequence identity, thereby serving as a substrate for homologous recombination reactions." homology " refers to that a DNA sequence is identical or has a common sequence identity to a corresponding or "complementary" sequence. The sequence identity between a given target site and the corresponding homology arms found on a targeting vector can be any degree of sequence identity that allows homologous recombination to occur. For example, the amount of the sequence identity shared by the homology arms (or its fragment) of the targeting vector and the target site (or its fragment) can be at least 51%, 53%, 57%, 60%, 65%, 70%, 75%, 80%, 83%, 85%, 87%, 89%, 91%, 93%, 95%, 97%, 98%, 99% or 100% sequence identity, so the sequence undergoes homologous recombination. In addition, the complementary region of homology between homology arms and complementary target sites can have any length that is enough to promote homologous recombination at the recognition site of cracking. Therefore, the homology arms have enough homology to carry out homologous recombination with the corresponding target site in the genome of the cell. For ease of reference, homology arms are mentioned in this article as 5' homology arms and 3' homology arms. The term relates to the relative position of homology arms and the inserted nucleic acid in the targeting vector.

In some embodiments, the homology arms of the targeting vector can have any length sufficient to promote homologous recombination events with corresponding target sites, including, for example, at least 5-10 kb, 5-15 kb, 10-20 kb, 20-30 kb, 30-40 kb, 40-50 kb, 50-60 kb, 60-70 kb, 70-80 kb, 80-90 kb, 90-100 kb, 100-110 kb, 110-120 kb, 120-130 kb, 130-140 kb, 140-150 kb, 150-160 kb, 160-170 kb, 170-180 kb, 180-190 kb, 190-200 kb long or longer. As further detailed below, targeting vectors can employ targeting arms of greater length. In a specific embodiment, the sum of the 5' homology arm and the 3' homology arm is at least 10 kb, or the sum of the 5' homology arm and the 3' homology arm is at least about 16 kb to about 100 kb or about 30 kb to about 100 kb. In other embodiments, the size of the sum of the 5' homology arm and the 3' homology arm of ACE2 is about 10 kb to about 150 kb, about 10 kb to about 100 kb, about 10 kb to about 75 kb, about 20 kb to about 150 kb, about 20 kb to about 100 kb, about 20 kb to about 75 kb, about 30 kb to about 150 kb, about 20 kb to about 100 kb, about 20 kb to about 75 kb, about 30 kb to about 15 kb, about 10 kb to about 30 kb, about 20 kb to about 40 kb, about 40 kb to about 60 kb, about 60 kb to about 80 kb, about 80 kb to about 100 kb, about 100 kb to about 120 kb, or about 120 kb to about 150 kb.

Certain embodiments herein relate to humanized gene-edited mammals, the genome of which includes a polyribonucleic acid encoding a full-length ACE2 protein of a human. For example, the polyribonucleic acid is operably linked to a promoter polyribonucleic acid. In some embodiments, the humanized gene-edited mammal does not express all or part of the polyribonucleic acid encoding the endogenous ACE2 protein of the humanized gene-edited mammal, and the polyribonucleic acid encoding the human ACE2 protein includes a modification of the human ACE2 protein gene.

In some embodiments, the cell is a pluripotent cell, a non-pluripotent cell, a mammalian cell, a human cell, a non-human mammalian cell, a rodent cell, a mouse cell, a hamster cell, a non-human pluripotent cell, a human pluripotent cell, a rodent pluripotent cell, or a fibroblast or a lung cell.

In some of the above methods, the cell is a primary cell or an immortalized cell. In some of the above methods, the rodent pluripotent cell is a mouse or rat embryonic stem (ES) cell.

In some of the above methods, the animal cell or the human cell is a primary cell or an immortalized cell.

In some of the above methods, the animal cell or the human cell is a pluripotent cell. In some of the above methods, the animal pluripotent cell is a mouse embryonic stem (ES) cell. In some of the above methods, the human pluripotent cell is a human embryonic stem (ES) cell, a human adult stem cell, a developmentally restricted human progenitor cell or a human induced pluripotent stem (iPS) cell.

In some embodiments, certain embodiments herein provide humanized gene-edited cells, and in particular, also provide isolated human and non-human totipotent or pluripotent stem cells, in particular mouse embryonic stem cells, which are capable of maintaining pluripotency after one or more continuous gene modifications in vitro and are capable of transmitting the targeted gene modifications to offspring via the germline.

The term "embryonic stem cell" or "ES cell" used herein includes an embryonic omnipotence or multipotency cell that can promote any tissue of the developing embryo after being introduced into the embryo. The term "pluripotent cell" used herein includes an undifferentiated cell with the ability to develop into more than one type of differentiated cell. The term "non-pluripotent cell" includes cells that are not pluripotent cells.

In some of the above methods, the targeted gene editing simultaneously comprises deleting an endogenous nucleic acid sequence at the target genomic locus or inserting the nucleic acid at the target genomic locus.

In some embodiments, the gene modification or gene editing includes two or more modifications independently implemented to cells (e.g., eukaryotic cells, non-rat eukaryotic cells, mammalian cells, cell-like cells, non-human mammalian cells, pluripotent cells, non-pluripotent cells, non-human pluripotent cells, human pluripotent cells, human ES cells, human adult stem cells, developmentally restricted human progenitor cells, human iPS cells, human cells, rodent cells, non-rat rodent cells, rat cells, mouse cells, hamster cells, fibroblasts or Chinese hamster ovary (CHO) cells). The first modification can be achieved by electroporation or any other method known in the art. Subsequently, the same cell genome is modified for the second time using a suitable second nucleic acid construct. The third modification can be achieved by a second electroporation or any other method known in the art. In various embodiments, after the first gene modification and the second gene modification of the same cell, the third gene modification, the fourth gene modification, the fifth gene modification, the sixth gene modification, etc. can be achieved (continuously) using, for example, continuous electroporation or any other suitable method known in the art.

In some embodiments, the present invention uses a targeting vector homologous recombination method to perform gene editing and insert exogenous nucleic acid into an endogenous genome.

In some embodiments, the insert nucleic acid comprises inserting a homologous or orthologous human nucleic acid sequence or replacing a eukaryotic, non-rat eukaryotic, mammalian, human or non-human mammalian nucleic acid sequence with it.

In some embodiments, the given inserted polynucleotide can be from any organism, including, for example, a rodent, a non-rat rodent, a rat, a mouse, a hamster, a mammal, a non-human mammal, a eukaryote, a non-rat eukaryote, a human, an agricultural animal, or a domesticated animal.

In a specific embodiment, the insertion nucleic acid may include a nucleic acid from a rat, which may include a fragment of a genomic DNA, a cDNA, a regulatory region, or any portion or combination thereof. In other embodiments, the insertion nucleic acid may include a nucleic acid from a eukaryote, a non-rat eukaryote, a mammal, a human, a non-human mammal, a rodent, a non-rat rodent, a human, a rat, a mouse, a hamster, a rabbit, a pig, a cow, a deer, a sheep, a goat, a chicken, a cat, a dog, a white melt, a primate (e.g., a marmoset, a rhesus monkey), a domestic mammal, or an agricultural mammal, or any other target organism. As outlined in more detail herein, the insertion nucleic acid used in various methods and compositions may cause "humanization" of the target locus.

In one embodiment, the genetic modification is to add a nucleic acid sequence. In one embodiment, the insert nucleic acid comprises a genetic modification in a coding sequence. In one embodiment, the genetic modification comprises a deletion mutation of a coding sequence. In one embodiment, the genetic modification comprises a fusion of two endogenous coding sequences. In one embodiment, the insert nucleic acid comprises inserting a homologous or orthologous human nucleic acid sequence or replacing a eukaryotic, non-rat eukaryotic, mammalian, human or non-human mammalian nucleic acid sequence with it. In one embodiment, the insert nucleic acid comprises inserting a homologous or orthologous human nucleic acid sequence into an endogenous mouse gene coding region comprising a corresponding mouse DNA sequence or replacing a mouse DNA sequence with it. In one embodiment, the insert nucleic acid comprises inserting a homologous or orthologous human nucleic acid sequence into an endogenous mouse gene coding region comprising a corresponding mouse DNA sequence or replacing a mouse DNA sequence with it. In one embodiment, a targeting vector is used to insert a hACE2 sequence at the start ATG site of the EXON1 CDS immediately following mAce2 for the mouse Ace2 site.

In one embodiment, the nucleic acid sequence of the targeting vector may include a polynucleotide that will generate a genetic modification of the region of the ACE2 locus of a mammal, a human or a non-human mammal when integrated into the genome, wherein the genetic modification at the ACE2 locus causes a decrease in ACE2 activity, an increase in ACE2 activity or an adjustment in ACE2 activity. In one embodiment, the ACE2 gene is completely replaced.

In one embodiment, the insert nucleic acid may comprise a regulatory element, including, for example, a promoter, enhancer or transcription factor.

In some embodiments, a given inserted polynucleotide and/or the corresponding replaced region of a mammalian, human cell, or non-human mammalian locus may be a coding region, an intron, an exon, an untranslated region, a regulatory region, a promoter, or an enhancer, or any combination thereof.

Provided herein are methods that allow for targeted integration of one or more polynucleotides of interest into a target locus, as outlined above, introduction of sequences, and gene-edited cells produced thereby."Introduction" is the presentation of a sequence into a cell (polypeptide or polynucleotide) in such a way that the sequence enters the interior of the cell.

Any cell from any organism can be used in the method provided herein.In a specific embodiment, the cell is from eukaryotic organism, non-rat eukaryotic organism, mammal, non-human mammal, mankind, rodent, non-rat rodent, rat, mouse or hamster.In a specific embodiment, the cell is eukaryotic cell, non-rat eukaryotic cell, pluripotent cell, non-pluripotent cell, non-human pluripotent cell, non-human mammal cell, human pluripotent cell, human ES cell, human adult stem cell, development-restricted human progenitor cell, human induced pluripotent cell (iPS) cell, mammalian cell, human cell, fibroblast, rodent cell, non-rat rodent cell, rat cell, mouse cell, mouse ES cell, hamster cell or CHO cell.

In some embodiments, the cell employed in the method has the DNA construct stably incorporated into its locus."Stably incorporated" or "stably introduced" refers to the introduction of a polynucleotide into a cell so that the nucleotide sequence is integrated into the genome of the cell and can be inherited by its progeny.

In one embodiment, introduction of one or more polynucleotides into a cell is mediated by electroporation, intracytoplasmic injection, viral infection, adenovirus, lentivirus, retrovirus, transfection, lipid-mediated transfection, or via Nucleofection™.

In one embodiment, the expression construct is introduced together with the introduced nucleic acid.

In one embodiment, the introduction of the one or more polynucleotides into the cell can be performed multiple times over a period of time. In one embodiment, the introduction of the one or more polynucleotides into the cell can be performed at least twice over a period of time, at least three times over a period of time, at least four times over a period of time, at least five times over a period of time, at least six times over a period of time, at least seven times over a period of time, at least eight times over a period of time, at least nine times over a period of time, at least ten times over a period of time, at least eleven times over a period of time, at least twelve times over a period of time, at least thirteen times over a period of time, at least fourteen times over a period of time, at least fifteen times over a period of time, at least sixteen times over a period of time, at least seventeen times over a period of time, at least eighteen times over a period of time, at least nineteen times over a period of time, or at least twenty times over a period of time.

In one embodiment, the targeting vector (containing the introduced nucleic acid) and the expression vector (containing the sgRNA) are introduced into the cell simultaneously.

In one embodiment, a method for making a humanized non-human animal is further provided, comprising: (a) modifying the genome of pluripotent cells to form donor cells with a targeting vector comprising an insertion nucleic acid, wherein the insertion nucleic acid comprises a human nucleic acid sequence; (b) the donor cell is introduced into a host embryo; and (c) the host embryo is bred in a surrogate mother, wherein the surrogate mother generates a progeny comprising the human nucleic acid sequence. In one embodiment, the donor cell is introduced into a host embryo in a blastocyst segment or in a pre-morula stage (i.e., 4-cell stage or 8-cell stage). In a further embodiment, the genetic modification can be transmitted via germline.

In a specific embodiment, a method for making a humanized mouse is provided, the method comprising: (a) introducing a targeting vector comprising an ACE2 gene fragment and an expression vector connected to an sgRNA into mouse embryonic cells to form gene-edited donor cells; (b) introducing the donor cells into mouse embryos; and (c) gestating the mouse embryos in a surrogate mother, wherein the surrogate mother generates offspring comprising the human ACE2 sequence.

Example 1 Construction of Ace2 gene sgRNA 1 and pX330-sgRNA plasmid

Synthesize the sgRNA1 sequence that recognizes the target site.

sgRNA1 sequence (SEQ ID NO:1): 5’-tactgctcagtccctcaccgagg-3’

The upstream and downstream annealing primers for synthesizing sgRNA by introducing BbsI restriction site into sgRNA site were used for subsequent annealing experiments. The upstream and downstream single-stranded primer sequences for synthesizing sgRNA1 are as follows:

Upstream: 5'-caccgtactgctcagtccctcaccg-3' (SEQ ID NO: 6)

Downstream: 5’-aaaccggtgagggactgagcagtac-3’(SEQ ID NO:7)

Source of pX330 plasmid: See Figure 1 for the map of pX330 vector. The plasmid backbone is from Miaoling Plasmid Platform, catalog number P0123.

The above sgRNA annealing primers were ligated to the pX330 plasmid (the plasmid was linearized with BbsI first) after annealing to obtain the expression vector pX330-sgRNA1.

The specific ligation reaction system is shown in Table 1.

Table 1 Ligation reaction system

sgRNA annealing product 1μL(0.5μM) pX330-sgRNA vector 1μL(20ng) T4 DNALigase 1μL(5U) 10×T4 DNA Ligase buffer 1μL _H2O Make up to 10 μL

The reaction conditions are as follows: connect at 16°C for more than 30 min, transform into 30 μL TOP10 competent cells, then take 200 μL and spread on the Amp-resistant plate, culture at 37°C for at least 12 hours, select 2 clones and inoculate into LB medium (5 mL) containing Amp resistance, and culture at 37°C and 250 rpm for at least 12 hours.

The randomly selected clones were sent to a sequencing company for sequencing verification. The sequencing results are shown in Figure 2. The correctly connected expression vector pX330-sgRNA1 was selected for subsequent experiments.

Example 2 Construction of Ace2 gene sgRNA2 and pX330-sgRNA2 plasmid

Synthesize the sgRNA2 sequence that recognizes the target site.

sgRNA2-Sequence (SEQ ID NO:2): 5’-cttggcattttcctcggtgaggg-3’

The upstream and downstream annealing primers for synthesizing sgRNA by introducing BbsI restriction site into sgRNA site were used for subsequent annealing experiments. The upstream and downstream single-stranded primer sequences for synthesizing sgRNA2 are as follows:

Upstream: 5’-caccgcttggcattttcctcggtga-3’(SEQ ID NO:4)

Downstream: 5'-aaactcaccgaggaaaatgccaagc-3' (SEQ ID NO: 5)

Source of pX330 plasmid: See Figure 1 for the map of pX330 vector. The plasmid backbone is from Miaoling Plasmid Platform, catalog number P0123.

The above sgRNA annealing primers were ligated to the pX330 plasmid (the plasmid was linearized with BbsI) after annealing to obtain the expression vector pX330-sgRNA2.

The specific ligation reaction system is shown in Table 2.

Table 2 Ligation reaction system

sgRNA annealing product 1μL(0.5μM) pX330-sgRNA vector 1μL(20ng) T4 DNA Ligase 1μL(5U) 10×T4 DNA Ligase buffer 1μL _H2O Make up to 10 μL

The reaction conditions are as follows: connect at 16°C for more than 30 min, transform into 30 μL TOP10 competent cells, then take 200 μL and spread on the Amp-resistant plate, culture at 37°C for at least 12 hours, select 2 clones and inoculate into LB medium (5 mL) containing Amp resistance, and culture at 37°C and 250 rpm for at least 12 hours.

The randomly selected clones were sent to a sequencing company for sequencing verification. The sequencing results are shown in Figure 3. The correctly connected expression vector pX330-sgRNA2 was selected for subsequent experiments.

Example 3 Identification of pX330-sgRNA Cutting Efficiency

2 μg of pX330-sgRNA plasmid prepared in Example 1 and Example 2 were transfected into mouse embryonic stem cells using Lipofectamine 3000 (Invitrogen, Cat. No. L3000001). For specific transfection operations, refer to the Lipofectamine 3000 reagent operation instructions. Mouse embryonic stem cells were collected two days after transfection, and genome extraction was performed using a cell genome extraction kit (Tiangen, DP304-02). Subsequently, PCR upstream and downstream primers were designed on both sides of the genome cleavage site, and the upstream primer (5arm-sgF: ggttttgatttggccataaaatgttagc (SEQ ID NO: 10)) and the downstream primer (3arm-sgR: attcccaggtccagtttcacctaag (SEQ ID NO: 11)) were subjected to PCR reaction (using Novozyme Phanta Max Super-Fidelity DNA Polymerase) on the extracted genome. Then, T7 endonuclease I (T7EⅠ) (Biolabs, M0302L) was used to verify the cutting efficiency of pX330-sgRNA. The principle is that T7 endonuclease I can recognize and cut incompletely paired DNA.

Specific steps of T7 EⅠ experiment:

The genomes were extracted from the cells transfected with pX330-sgRNA1 and pX330-sgRNA2, and the PCR products obtained by 5arm-sgF+3arm-sgR amplification were recovered (Tian Gen, DP214-02), and 1 μg was taken for annealing reaction. The system is as follows:

Table 3

PCR products 1 μg Buffer 2 2μL _H2O Make up to 20 μL Reaction conditions Boil in a water bath for 10 minutes and then cool naturally

Then, 1 μL of T7 endonuclease I was added to the annealed product and reacted at 37°C for 30 min, and then directly run on the gel for verification. The gel running results are shown in Figure 4. The cleavage bands of sgRNA1 and sgRNA2 in Example 1 and Example 2 were brighter (sgRNA1 can be cleaved into two bands of about 376 bp and 581 bp, and sgRNA2 can be cleaved into two bands of about 371 bp and 586 bp), and had a higher cleavage efficiency.

Since the cutting efficiency is mainly displayed through the graph, in order to show the effects of the schemes of Examples 1 and 2, the cutting efficiency of another sgRNA (referred to as sgRNA3) is also listed in FIG4 .

The listed sgRNRA3 sequence (SEQ ID NO:3): 5'-caagtgaactttgataagacagg-3'

The upstream and downstream single-stranded primer sequences for synthesizing sgRNA3 are as follows:

Upstream: 5’-caccgcaagtgaactttgataagac-3’(SEQ ID NO:8)

Downstream: 5'-aaacgtcttatcaaagttcacttgc-3' (SEQ ID NO: 9)

The remaining steps were the same as in Example 1. Randomly selected clones were sent to a sequencing company for sequencing verification. The sequencing results are shown in FIG5 . The correctly connected expression vector pX330-sgRNA3 was selected for subsequent experiments.

Since the construction of other sgRNAs and pX330-sgRNA plasmids is not the focus of the embodiments of the present invention, they are not described or listed in detail.

Example 4 Design of Targeting Vector

After inserting the CDS protein coding sequence of the human ACE2 gene (Gene ID: ID: 59272) (based on the transcript with NCBI accession number NM_001371415.1→NP_001358344.1, its CDS sequence is shown in hACE2-CDS SEQ ID NO: 12, and the protein sequence is shown in hACE2-protein SEQ ID NO: 13) into the promoter and 5'UTR region sequence of mouse Ace2, the mouse Ace2 promoter was used to start the expression of human ACE2 gene. At the same time, the inserted human ACE2 CDS sequence was followed by an SV40 polyA sequence signal (SV40-polyA sequence is shown in SEQ ID NO: 14) termination signal to strengthen the termination of human ACE2 mRNA transcription.

The hACE2-CDS sequence is as follows (SEQ ID NO: 12):

atgtcaagctcttcctggctccttctcagccttgttgctgtaactgctgctcagtccaccattgaggaacaggccaagacatttttggacaagtttaaccacgaagccgaagacctgttctatcaaagttcacttgcttcttggaattataacaccaatattactgaagagaatgtccaaaacatgaataatgctggggacaaaatgg tctgcctttttaaaggaacagtccacacttgcccaaatgtatccactacaagaaattcagaatctcacagtcaagcttcagctgcaggctcttca gcaaaatgggtcttcagtgctctcagaagacaagagcaaacggttgaacacaattctaaatacaatgagcaccatctacagtactggaaaagtttgtaacccagataatccacaagaatgcttattacttgaaccaggtttgaatgaaataatggcaaacagtttagactacaatgagaggctctgggcttgggaaagctggagatctgaggtcgg caagcagctgaggccattatatgaagagtatgtggtcttgaaaaatgagatggcaagagcaaatcattatgaggactatggggatt attggagaggagactatgaagtaaatggggtagatggctatgactacagccgcggccagttgattgaagatgtggaacatacctttgaagagattaaaccattatatgaacatcttcatgcctatgtgagggcaaagttgatgaatgcctatccttcctatatcagtccaattggatgcctccctgctcatttgcttggtgatatgtgggg tagattttggacaaatctgtactctttgacagttccctttggacagaaaccaaacatagatgttactgatgcaatggtggaccaggcctgg gatgcacagagaatattcaaggaggccgagaagttctttgtatctgttggtcttcctaatatgactcaaggattctgggaaaattccataacggacccaggaaatgttcagaaagcagtctgccatcccacagcttgggacctggggaagggcgacttcaggatccttatgtgcacaaaggtgacaatggacgacttcctgaca gctcatcatgagatggggcatatccagtatgatatggcatatgctgcacaaccttttctgctaagaaatggagctaatgaaggattccatgaagct gttggggaaatcatgtcactttctgcagccacacctaagcatttaaaatccattggtcttctgtcacccgattttcaagaagacaatgaaacagaaataaacttcctgctcaaacaagcactcacgattgttgggactctgccatttacttacatgttagagaagtggaggtggatggtctttaaaggggaaattcccaaagaccagtggatgaa aaagtggtgggagatgaagcgagagatagttggggtggtggaacctgtgccccatgatgaaacatactgtgaccccgcatctctgtt ccatgtttctaatgattactcattcattcgatattacacaaggaccctttaccaattccagtttcaagaagcactttgtcaagcagctaaaacatgaaggccctctgcacaaatgtgacatctcaaactctacagaagctggacagaaactgttcaatatgctgaggcttggaaaatcagaaccctggaccctagcattggaaaatgttgtaggag caaagaacatgaatgtaaggccactgctcaactactttgagcccttatttacctggctgaaagaccagaacaagaattcttttgtgg gatggagtaccgactggagtccatatgcagaccaaagcatcaaagtgaggataagcctaaaatcagctcttggagataaagcatatgaatggaacgacaatgaaatgtacctgttccgatcatctgttgcatatgctatgaggcagtactttttaaaagtaaaaaatcagatgattctttttggggaggaggatgtgcgagtggc taatttgaaaccaagaatctcctttaatttctttgtcactgcacctaaaaatgtgtctgatatcattcctagaactgaagttgaaaaggccatcagg atgtcccggagccgtatcaatgatgctttccgtctgaatgacaacagcctagagtttctggggatacagccaacacttggacctcctaaccagccccctgtttccatatggctgattgtttttggagttgtgatggggagtgatagtggttggcattgtcatcctgatcttcactggggatcagagatcggaagaagaaaaaata aagcaagaagtggagaaaatccttatgcctccatcgatattagcaaaggagaaaataatccaggattccaaaacactgatgatgttcagacctccttttag

The hACE2-protein sequence is as follows (SEQ ID NO: 13):

SV40 polyA sequence (SEQ ID NO: 14):

aacttgtttattgcagcttataatggttacaaataaagcaatagcatcacaaatttcacaaataaagcatttttttcactgcattctagttgtggtttgtccaaactcatcaatgtatctta

According to the sequence design, the inventor further designed a targeting scheme as shown in Figure 6 and a vector comprising a 5' homology arm (5arm), a human ACE2 gene fragment, and a 3' homology arm (3arm). Wherein the 5' homology arm is the 125683-126652 nucleotides of the NCBI accession number AC091606.8 (the 5' homology arm sequence is shown in SEQ ID NO: 15), and the 3' homology arm is the 126796-127766 nucleotides of the NCBI accession number AC091606.8 (the 3' homology arm sequence is shown in SEQ ID NO: 16). At the same time, the PGK-puromycin heterologous gene package is also inserted into the vector for screening needs, and a pair of frt sites (SEQ ID NO: 18) are designed at both ends of the puromycin resistance gene (PGK-puro, SEQ ID NO: 17) expression frame, so FLP recombinase can be used to remove and solve the safety problems caused by transgenics. The constructed vector is fully sequence verified. Prior to targeting, the vector was linearized by AgeI (a schematic diagram of the targeting vector and a schematic diagram of the targeting strategy are shown in FIG6 ).

5' homology arm sequence (SEQ ID NO: 15):

ccctatggagtggagaagagtcttataattttttaaatgggcagagaaatgaatttatttttaatttttagagacagggtttctttgtatagctctagctgtctttgattggtagacaaagctgtcctcaaactcagagatcttccttcctttgtctcctgagtgctgggattaaaggcatggaccaccactgccctgccccattctctccatta attttaagtgaatgcttgcaaaagctc acttctttggtgaacagcttcctttacaaataagtacctttgccttcgtttttaggattcttaaaaagaaaaaaagattcagccaggtggttgtggtgcacacctttaatcccagcagtcaggaggcagaggaaagcagatctcttgagtttgaggctagcctagtctacagagggagttccaggacagccaagg ctacagagaggaactgtctaaaaacaccaagaaagagagaaagga gagagggagaggatggatagcttattgatagaattgtcagaaaaggctataagttccaatatgtgtcccatgatttctaagtctagccctttctgttatagtaaaatcatagtacaccctcctcctccagtgtatctttaacagcttttaaggaacatattaactaaatgtccaggttttgatttggccataaaatgttagcaaagctaaggtt ttctaggattaatgaataacatgtcttt atttagtttacttaaaaaaatcattctaaaatatctgtttacatatctgtcctctccaggattaacttcatattggtccagcagcttgtttactgttctcttcttctgtttcttcttctgctttttttttcttctcttctcagtgcccaacccaagttcaaaggctgatgagagagaaaaactcatgaagagatttttactc tagggaaagttgctcagtggatgggatcttggcgcacggggaaag

3' homology arm sequence (SEQ ID NO: 16):

Gaattataatactaacattactgaagaaaatgcccaaaagatggtaagttcttgaggctacccagggggttattgattgcttcttaaagatcagaattactgcctataaaactggataaggaaatcatagagatctctcaagtgtgaggatgagtgactgcctctgtagctctgatcctagtctcccagatggctaaattcaattgaccttagagttcatctggaa aattgttatgaatgaa ttatttgcccagattccaaagatgagtgaaaatgtttaataaaagttgccatcactattctcattatttggtatgtaaagcattcatggaaatgttctaagtcgttatgagccaataattttctttagcttataatgccaacaggtctatccgagaactacaaatgacatattaactgaaaaatgcaactggggtttactgaagg cagcagcttagtaattaaggtaaccatggcttaggt gaaactggacctgggaattccttctttcattgacacagagctctgaggaatttccaaaggtcacagaagaaaagctataattaaactagtcccaaaaaatctcagcctactctgggaaagcagcatattttgtttgacaagtgcaaggacttagaacttttttttttctcactgatcctgaagtgccttttaagtatagttaagtggt ggaaaattgagcaactatttaagaaaagactcttt tttttcttcttccagcaatgctttccttcaaaacggtagcttcaaaacttcctgtcttttaaatgatcagggggctgtgtgtttaaattattgccattcatagaacagagtgggtctgaggatgcctgtttcctttgaaattctatgccccctcccagttttctaaaatttaagaaaccacagactttgacaatg tagttgccaaatgagttgcttttaactgctctaatagtttggtctt

PGK-puro sequence (SEQ ID NO: 17):

Gggtaggggaggcgcttttcccaaggcagtctggagcatgcgctttagcagccccgctgggcacttggcgctacacaagtggcctctggcctcgcacacattccacatccccccggtaggcgccaaccggctccgttctttggtggccccttcgcgccaccttctactcctcccctagtcaggaagttcccccccgcccc gcagctcgcgtcgtgcaggacgtgacaaatggaagtagcacgtctcactagtctcgtgcagatggacagcaccgctgagcaa tggaagcgggtaggcctttggggcagcggccaatagcagctttgctccttcgctttctgggctcagaggctgggaaggggtgggtccgggggcgggctcaggggcgggctcaggggcggggcgggcgcccgaaggtcctccggaggcccggcattctgcacgcttcaaaagcgcacgtctgccgcg ctgttctcctcttcctcatctccgggcctttcgacctgcagcccaagctagcttaccatgaccgagtacaagcccacggtgcgcctcgccacccg cgacgacgtccccagggccgtacgcaccctcgccgccgcgttcgccgactaccccgccacgcgccacaccgtcgatccggaccgccacatcgagcgggtcaccgagctgcaagaactcttcctcacgcgcgtcgggctcgacatcggcaaggtgtgggtcgcggacgacggcgccgcggtgg cggtctggaccacgccggagagcgtcgaagcgggggcggtgttcgccgagatcggcccgcgcatggccgagttgagcggttcccggctggccgcgcagc aacagatggaaggcctcctggcgccgcaccggcccaaggagcccgcgtggttcctggccaccgtcggcgtctcgcccgaccaccagggcaagggtctgggcagcgccgtcgtgctccccggagtggaggcggccgagcgcgccggggtgcccgccttcctggagacctccgcgccccgcaacctcccc ttctacgagcggctcggcttcaccgtcaccgccgacgtcgaggtgcccgaaggaccgcgcacctggtgcatgacccgcaagcccggtgcctga

Frt sequence (SEQ ID NO:18): gaagttcctattctctgaaagtataggaacttc

The vector construction process is as follows:

Design the upstream primer (5arm-pcrF: tcgcacacattccacatccaccggtccctatggagtggagaagagtctta (SEQ ID NO: 19)) and the matching downstream primer (5arm-pcrR: gaaggagccaggaagagcttgacatctttccccgtgcgccaagatcc (SEQ ID NO: 20)) for amplifying the bridging fragment of the 5' homology arm;

Design an upstream primer (hACE2-F: ggatcttggcgcacggggaaagatgtcaagctcttcctggctccttc (SEQ ID NO: 21)) and a matching downstream primer (hACE2-R: cattataagctgcaataaacaagttctaaaaggaggtctgaacatcatc (SEQ ID NO: 22)) for amplifying the bridging fragment of human ACE2 CDS;

Design an upstream primer (SV40-F: gatgatgttcagacctccttttagaacttgtttattgcagcttataatg (SEQ ID NO: 23)) and a matching downstream primer (SV40-R: AGAGAATAGGAACTTCGCACGCGTtaagatacattgatgagtttggac (SEQ ID NO: 24)) for amplifying the bridge fragment of SV40 polyA;

The upstream primer (3arm-pcrF: tacgaagttatGtcgacgcGGCGCGCCgaattataatactaacattactg (SEQ ID NO: 25)) and the matching downstream primer (3arm-pcrR: tatgaccatgattacgccaagcttaagaccaaactattagagcagttaaaagc (SEQ ID NO: 26)) for amplifying the 3' homology arm fragment were designed. The amplification templates of the 5' homology arm and the 3' homology arm were the C57BL6/J mouse genome, and the amplification template of human ACE2 was human lung cell cDNA. The PCR reaction system (using Novozyme Phanta Max Super-Fidelity DNA Polymerase) and conditions are shown in Table 4:

Table 4 PCR reaction system (50 μL)

If so, the 5' homology arm of the product fragment obtained by PCR amplification, human ACE2 CDS, and SV40 polyA are PCR-amplified into a continuous fragment 5arm-hACE-SV40 using the overlap PCR (overlap PCR) and touch down PCR method; and the 3' homology arm obtained by PCR amplification is directly used to construct a homologous recombination targeting vector after recovery. The construction process is as follows:

1. The 5arm-hACE-SV40 fragment was double-digested with AgeI+MluI; the 3' homology arm fragment was double-digested with AscI+HindIII and then connected by enzyme digestion and ligation to obtain a targeting vector. 2. After enzyme digestion identification, the obtained positive targeting vector was sent for sequencing identification. The sequencing company verified that the sequence was correct (as shown in Figure 7), thus successfully obtaining a humanized ACE2 targeting vector, the sequence is as follows:

The entire targeting vector sequence (SEQ ID NO: 27):

tcgcgcgtttcggtgatgacggtgaaaacctctgacacatgcagctcccggagacggtcacagcttgtctgtaagcggatgccgggagcagacaagcccgtcagggcgcgtcagcgggtgttggcgggtgtcggggctggcttaactatgcggcatcagagcagattgtactgagagtgcaccatat gtaccgggtaggggaggcgcttttcccaaggcagtctggagcatgcgctttagcagccccgctgggcacttggcgct acacaagtggcctctggcctcgcacacattccacatccaccggtccctatggagtggagaagagtcttataattttttaaatgggcagagaaatgaatttatttttaatttttagagacagggtttctttgtatagctctagctgtctttgattggtagacaaagctgtcctcaaactcagagatcttccttcctttgtctcctgagt gctgggattaaaggcatggaccaccactgcctgccccattctctccattaatttta agtgaatgcttgcaaaagctcacttctttggtgaacagcttcctttacaaataagtacctttgccttcgttttataggattcttaaaaagaaaaaaaaagattcagccaggtggttgtggtgcacacctttaatcccagcagtcaggaggcagaggaaagcagatctcttgagtttgaggctagcctagtctacaga gggagttccaggacagccaaggctacagagaggaactgtctaaaaacaccaagaaagagagaaagga gagagggagaggatggatagcttattgatagaattgtcagaaaaggctataagttccaatatgtgtcccatgatttctaagtctagccctttctgttatagtaaaatcatagtacaccctcctcctccagtgtatctttaacagcttttaaggaacatattaactaaatgtccaggttttgatttggccataaaatgttagcaaagctaaggtt ttctaggattaatgaataacatgtctttatttagtttacttaaaaaaatca ttctaaaatatctgtttacatatctgtcctctccaggattaacttcatattggtccagcagcttgtttactgttctcttcttctgtttcttcttctgctttttttttcttctcttctcagtgcccaacccaagttcaaaggctgatgagagagaaaaaactcatgaagagattttactctagggaaagttgctcagtgg atgggatcttggcgcacggggaaagatgtcaagctcttcctggctccttctcagccttgttgctgtaac tgctgctcagtccaccattgaggaacaggccaagacatttttggacaagtttaaccacgaagccgaagacctgttctatcaaagttcacttgcttcttggaattataacaccaatattactgaagagaatgtccaaaacatgaataatgctggggacaaatggtctgcctttttaaaggaacagtccacacttgcccaaatgtatccact acaagaaattcagaatctcacagtcaagcttcagctgcaggctcttcagcaaaat gggtcttcagtgctctcagaagacaagagcaaacggttgaacacaattctaaatacaatgagcaccatctacagtactggaaaagtttgtaacccagataatccacaagaatgcttattacttgaaccaggtttgaatgaaataatggcaaacagtttagactacaatgagaggctctgggcttgggaaagctggagatctgaggtcggcaagcag ctgaggccattatatgaagagtatgtggtcttgaaaaatgagatggcaa gagcaaatcattatgaggactatggggattattggagaggagactatgaagtaaatggggtagatggctatgactacagccgcggccagttgattgaagatgtggaacatacctttgaagagattaaaccattatatgaacatcttcatgcctatgtgagggcaaagttgatgaatgcctatccttcctatatcagtccaattggatgcctccctgctcatt tgcttggtgatatgtggggtagattttggacaaatctgtactc tttgacagttccctttggacagaaaccaaacatagatgttactgatgcaatggtggaccaggcctgggatgcacagagaatattcaaggaggccgagaagttctttgtatctgttggtcttcctaatatgactcaaggattctgggaaaattccatgctaacggacccaggaaatgttcagaaagcagtctgccatcccaca gcttgggacctggggaagggcgacttcaggatccttatgtgcacaaaggtgacaatggacga cttcctgacagctcatcatgagatggggcatatccagtatgatatggcatatgctgcacaaccttttctgctaagaaatggagctaagaaatggagctaatgaaggattccatgaagctgttggggaaatcatgtcactttctgcagccacaccctaagcatttaaaatccattggtcttctgtcacccgattttcaagaagacaatgaaacagaaataaacttcctg ctcaaacaagcactcacgattgttgggactctgccatttacttacatgtta gagaagtggaggtggatggtctttaaaggggaaattcccaaagaccagtggatgaaaaagtggtgggagatgaagcgagagatagttggggtggtggaacctgtgccccatgatgaaacatactgtgaccccgcatctctgttccatgtttctaatgattactcattcattcgatattacacaaggaccctttaccaattccagtttcaagaagc actttgtcaagcagctaaacatgaaggccctctgcacaaatgtgacatct caaactctacagaagctggacagaaactgttcaatatgctgaggcttggaaaatcagaaccctggaccctagcattggaaaatgttgtaggagcaaagaacatgaatgtaaggccactgctcaactactttgagcccttatttacctggctgaaagaccagaacaagaattcttttgtgggatggagtaccgactggagtccatatgcagaccaaagcat caaagtgaggataagcctaaaatcagctcttggagataaagcata tgaatggaacgacaatgaaatgtacctgttccgatcatctgttgcatatgctatgaggcagtactttttaaaagtaaaaaatcagatgattctttttggggaggaggatgtgcgagtggctaatttgaaaccaagaatctcctttaatttctttgtcactgcacctaaaaatgtgtctgatatcattcctagaactga agttgaaaaggccatcaggatgtcccggagccgtatcaatgatgctttccgtctgaatgacaacag cctagagtttctggggatacagccaacacttggacctcctaaccagccccctgtttccatatggctgattgtttttggagttgtgatgggagtgatagtggttggcattgtcatcctgatcttcactgggatcagagatcggaagaagaaaaataaagcaagaagtggagaaaaatccttatgcctccatcgatattagcaaaggaga aaataatccaggattccaaaacactgatgatgttcagacctccttttagaacttgttt attgcagcttataatggttacaaataaagcaatagcatcacaaatttcacaaaaagcattttttcactgcattctagttgtggtttgtccaaactcatcaatgtatcttaacgcgtgcgaagttcctattctctagaaagtataggaacttcatcgataccgggtaggggaggcgcttttcccaaggcagtctggagcatgc gctttagcagccccgctgggcacttggcgctacacaagtggcctctggcctcgcacacat tccacatcccccggtaggcgccaaccggctccgttctttggtggccccttcgcgccaccttctactcctcccctagtcaggaagttccccccgccccgcagctcgcgtcgtgcaggacgtgacaaatggaagtagcacgtctcactagtctcgtgcagatggacagcaccgctgagcaatggaagcggg taggcctttggggcagcggccaatagcagctttgctccttcgctttctgggctcagaggctgggaaggggtgggt ccgggggcgggctcaggggcgggctcaggggcggggcgggcgcccgaaggtcctccggaggcccggcattctgcacgcttcaaaagcgcacgtctgccgcgctgttctcctcttcctcatctccgggcctttcgacctgcagcccaagctagcttaccatgaccgagtacaagcccacggtgcgcctcgcc acccgcgacgacgtccccagggccgtacgcaccctcgccgccgcgttcgccgactaccccgccacgcgccaca ccgtcgatccggaccgccacatcgagcgggtcaccgagctgcaagaactcttcctcacgcgcgtcgggctcgacatcggcaaggtgtgggtcgcggacgacggcgccgcggtggcggtctggaccacgccggagagcgtcgaagcgggggcggtgttcgccgagatcggcccgcgcatggcc gagttgagcggttcccggctggccgcgcagcaacagatggaaggcctcctggcgccgcaccggcccaaggagcccgcgtggtt cctggccaccgtcggcgtctcgcccgaccaccagggcaagggtctgggcagcgccgtcgtgctccccggagtggaggcggccgagcgcgccggggtgcccgccttcctggagacctccgcgccccgcaacctccccttctacgagcggctcggcttcaccgtcaccgccgacgtcgaggtgccc gaaggaccgcgcacctggtgcatgacccgcaagcccggtgcctgaggtacctctcatgctggagttcttcgcccacccca acttgtttattgcagcttataatggttacaaataaagcaatagcatcacaaatttcacaaataaagcatttttttcactgcattctagttgtggtttgtccaaactcatcaatgtatcttatcatcgatgaagttcctattctctagaaagtataggaacttctaacctcccgggtgacagataacttcgtataatgtatgctatacga agttatgtcgacgcggcgcgccgaattataatactaacattactgaagaaaatgcc caaaagatggtaagttcttgaggctacccagggggttattgattgattgcttcttaaagatcagaattactgcctataaaactggataaggaaatcatagagatctctcaagtgtgaggatgagtgactgcctctgtagctctgatcctagtctcccagatggctaaattcaattgaccttagagttcatctggaaaattgttatgaatgaattatttgcccagattc caaagatgagtgaaaatgtttaataaagttgccatcacta ttctcattatttggtatgtaaaagcattcatggaaatgttctaagtcgttattgagccaataattttctttagcttataatgccaacaggtcttccgagaactacaaatgacatattaactgaaaaatgcaactggggtttaactgaaggcagcagcttagtaattaaggtaaccatggcttaggtgaaactggacctgggaattccttctttcat tgacacagagctctgaggaatttccaaaggtcacagaagaaaagctat aattaaactagtcccaaaaaatctcagcctactctgggaaagcagcatattttgtttgacaagtgcaaggacttagaactttttttttctcactgatcctgaagtgccttttaagtatagttaagtggtggaaaattgagcaactatttaagaaaagactctttttttttcttcttccagcaatgctttccttcaaaacggtag cttcaaaacttcctgtcttttaaatgatcagggggctgtgtgtttaaattattgccattca tagaacagagtgggtctgaggatgcctgtttcctttgaaattctatgccccctcccagttttctaaaatttaagaaaccacagagactttgacaatgtagttgccaaatgagttgcttttaactgctctaatagtttggtcttaagcttggcgtaatcatggtcatagctgtttcctgtgtgaaattgttatccg ctcacaattccacacaacatacgagccggaagcataaagtgtaaagcctggggtgcctaatgagtgagct aactcacattaattgcgttgcgctcactgcccgctttccagtcgggaaacctgtcgtgccagctgcattaatcggccaacgcgcggggagaggcggtttgcgtattgggcgctcttccgcttcctcgctcactgactcgctgcgctcggtcgttcggctgcggcgagcggtatcagct cactcaaaggcggtaatacggttatccacagaatcaggggataacgcaggaaagaacatgtgagcaaaaggccagcaaaagg ccaggaaccgtaaaaaggccgcgttgctggcgtttttccataggctccgcccccctgacgagcatcacaaaaatcgacgctcaagtcagaggtggcgaaacccgacaggactataaagataccaggcgtttccccctggaagctccctcgtgcgctctcctgttccgaccctgccgcttaccggatacctg tccgcctttctcccttcgggaagcgtggcgctttctcatagctcacgctgtaggtatctcagttcggtgtaggt cgttcgctccaagctgggctgtgtgcacgaaccccccgttcagcccgaccgctgcgccttatccggtaactatcgtcttgagtccaacccggtaagacacgacttatcgccactggcagcagccactggtaacaggattagcagagcgaggtatgtaggcggtgctacagagttcttgaagtggtggcctaactacggctac actagaagaacagtatttggtatctgcgctctgctgaagccagttaccttcggaaaaagagtt ggtagctcttgatccggcaaacaaaccaccgctggtagcggtggtttttttgtttgcaagcagcagattacgcgcagaaaaaaaggatctcaagaagatcctttgatcttttctacggggtctgacgctcagtggaacgaaaactcacgttaagggattttggtcatgagattatcaaaaaggatcttcacctag atccttttaaattaaaaatgaagttttaaatcaatctaaagtatatatgagtaaacttggtctgacagtt accaatgcttaatcagtgaggcacctatctcagcgatctgtctatttcgttcatccatagttgcctgactccccgtcgtgtagataactacgatacgggagggcttaccatctggccccagtgctgcaatgataccgcgagacccacgctcaccggctccagatttatcagcaataaaccagccagccggaagggccgagcgcagaag tggtcctgcaactttatccgcctccatccagtctattaattgttgccgggaagcta gagtaagtagttcgccagttaatagtttgcgcaacgttgttgccattgctacaggcatcgtggtgtcacgctcgtcgtttggtatggcttcattcagctccggttcccaacgatcaaggcgagttacatgatcccccatgttgtgcaaaaaagcggttagctccttcggtcctccgatcgttgt cagaagtaagttggccgcagtgttatcactcatggttatggcagcactgcataattctcttactgtcatgccatccgtaag atgcttttctgtgactggtgagtactcaaccaagtcattctgagaatagtgtatgcggcgaccgagttgctcttgcccggcgtcaatacgggataataccgcgccacatagcagaactttaaaagtgctcatcattggaaaacgttcttcggggcgaaaactctcaaggatcttaccgctgttgagatccagttcgat gtaacccactcgtgcacccaactgatcttcagcatcttttactttcaccagcgtttctgggtgagca aaaacaggaaggcaaaatgccgcaaaaaagggaataagggcgacacggaaatgttgaatactcatactcttcctttttcaatattattgaagcatttatcagggttattgtctcatgagcggatacatatttgaatgtatttagaaaaataaacaaataggggttccgcgcacatttccccgaaaagtgccacctgacgtcta agaaaccattattatcatgacattaacctataaaaataggcgtatcacgaggccctttcgtc

Comparative Example 1

The product fragment 5' homology arm, human ACE2 CDS, and SV40 polyA obtained by PCR amplification were PCR-amplified into a continuous fragment 5arm-hACE-SV40 using the overlap PCR method. The PCR reaction conditions are shown in Table 5, and the other conditions are the same as Example 4.

Table 5 PCR reaction system (50 μL)

The results are shown in FIG8 , and no 3-fragment junction fragment could be amplified.

Example 5 Obtaining humanized ACE2 mouse embryonic stem cells

In one embodiment, obtaining humanized ACE2 mouse embryonic stem cells can be performed as follows:

C57BL6/J mouse embryonic stem cells (the embryonic stem cells are derived from an established embryonic stem cell line) were revived from a liquid nitrogen frozen cell bank, and mouse embryonic stem cells within the generation of p10 were used, and cultured and grown in a 6 cm culture dish for 3 days.

Kit(Lonza，VPH-1001)小鼠胚胎干细胞电转试剂盒，使用A023程序，约2×10⁶个细胞被电穿孔，并且所述电转过程含有3μg线性化打靶载体以及1μg pX330-sgRNA1的100μL电转缓冲液中进行。所述转染细胞被种到3个6孔板的孔中，然后恢复36小时。恢复后，1μg/mL嘌呤霉素(默克公司)被加入到细胞培养基中。By using the Nucleofector ^TM IIs/2b electroporator and Mouse ES Cell

Kit (Lonza, VPH-1001) mouse embryonic stem cell electroporation kit, using the A023 program, about 2×10 ⁶ cells were electroporated, and the electroporation process was carried out in 100 μL electroporation buffer containing 3 μg of linearized targeting vector and 1 μg of pX330-sgRNA1. The transfected cells were seeded into three wells of a 6-well plate and then recovered for 36 hours. After recovery, 1 μg/mL puromycin (Merck) was added to the cell culture medium.

After 3-4 days of screening, puromycin-resistant mouse embryonic stem cell clones were picked and cultured in 96-well plates by using a glass needle to draw single clones. The next day, the single clones were trypsinized and divided into two cultures, one of which was lysed separately in 10 μL of NP 40 lysis buffer at 56°C for 60 minutes, followed by lysis at 95°C for 10 minutes.

Among them, the specific steps of mouse embryonic stem cell culture are: prepare the feeder layer feeder cells one day in advance, spread them in different well plates as needed, and culture them overnight to form a monolayer. The feeder layer feeder cells are mouse embryonic fibroblasts prepared by mitomycin C (MMC) method. Use mES culture medium containing LIF and 2i (chir99021 and pD0325901inhibitor) for culture, replace fresh culture medium every day, and increase the culture medium appropriately according to the growth of cells. Generally, one generation is passed every 3 days. During the passaging, use 0.25% trypsin to digest and plant at a density of about 300,000 per well in a 6-cm dish and 100,000 per well in a 6-well plate.

The composition of mES+LIF+2i culture medium is: Knockout DMEM (1×, gibco) + 15% FBS (FRONTBIOMEDICAL, filtered through 0.22μm Millipore filter) + GlutaMAX (100×, gibco) + NEAA (100×, gibco) + P/S (P: 50 units, S: 50 mg/ml, Hyclone) + β-mercaptoethanol (gibco, used at a concentration of 0.1 mM) + LIF (1000 units/ml, Millipore) + CHIR99021 (GSK3β inhibitor, used at a concentration of 3μM) + PD0325901 (MEK inhibitor, used at a concentration of 1μM).

The composition of NP40 lysis buffer is: 10 mL TE (20 mM Tris pH 8.0, 150 mM NaCl, 2 mM EDTA) + 0.5% NP40 + 10 μL proteinase K (10 mg/mL).

In the above method, pX330-sgRNA1 was replaced with pX330-sgRNA2 or pX330-sgRNA3, and the other steps were the same as pX330-sgRNA1.

The targeting effects of pX330-sgRNA1, pX330-sgRNA2 and pX330-sgRNA3 combined with targeting vectors are shown in Table 6.

Table 6. Targeting effect of sgRNA1-3 combined with targeting vector (number of surviving clones)

pX330-sgRNA1 pX330-sgRNA2 pX330-sgRNA3 231 187 43

Example 6 Identification of humanized ACE2 mouse embryonic stem cell genotype

The cell lysate obtained at the end of Example 5 was used as a genotype identification PCR screening template. PCR screening was performed according to the manufacturer's instructions using PhantaMax Super-Fidelity DNA Polymerase reagent (Novozyme). PCR analysis was used for directional insertion of HDR with 5' homology arms and 3' homology arms in the mouse Ace2 site. Since the ACE2 gene is located on the X chromosome, the mouse embryonic stem cells used are XY males, so there is no double allele targeting.

The upstream of the primer for identification of directional insertion is located inside the puromycin resistance (Puro-F: aacctccccttctacgagc (SEQ ID NO: 28)), and the downstream of the primer paired with it is located outside the 3' homology arm (3arm-outR: tacagccaggatctggatgtcagc (SEQ ID NO: 29)). If the insertion position of the recombinant vector is correct, a band with a length of 1504 bp should appear. At this time, the genomic sequence of the mouse embryonic stem cell Ace2 site is replaced with SEQ ID NO: 30:

ccctatggagtggagaagagtcttataattttttaaatgggcagagaaatgaatttatttttaatttttagagacagggtttctttgtatagctctagctgtctttgattggtagacaaagctgtcctcaaactcagagatcttccttcctttgtctcctgagtgctgggattaaaggcatggaccaccactgccctgccccattctctccattaatt ttaagtgaatgcttgcaaaagctcacttctttggtgaacagcttcctttacaaataagtacctttgccttcgtttttataggattcttaaaaagaaaaaaaaagattcagccaggtggttgtggtgcacacctttaatcccagcagtcaggag gcagaggaaagcagatctcttgagtttgaggctagcctagtctacagaggggagttccaggacagccaaggctacagagaggaactgtctaaaaacaccaagaaagagagaaaggagagagggagaggatggatagcttattgatagaattgtcagaaaaggctataagttccaatatgtgtcccatgatttctaagtctagccctttct gttatagtaaaatcatagtacaccctcctcctccagtgtatctttaacagcttttaaggaacatattaactaaatgtccaggttttgatttggccataaaatgttagcaaagctaaggttttctaggattaatgaataacatgtctttatttagtttactt aaaaaaatcattctaaaatatctgtttacatatctgtcctctccaggattaacttcatattggtccagcagcttgtttactgtctcttctgtttcttcttctgctttttttttcttctcttctcagtgcccaacccaagttcaaaggctgatgagagagaaaaactcatgaagagattttactctagggaaagtt gctcagtggatgggatcttggcgcacggggaaagatgtcaagctcttcctggctccttctcagccttgttgctgtaactgctgctcagtccaccattgaggaacaggccaagacatttttggacaagtttaaccacgaagccgaagacctgttctatcaaagttcacttgcttc ttggaattaacaccaatattactgaagagaatgtccaaaaacatgaataatgctggggacaaatggtctgcctttttaaaggaacagtccacacttgcccaaatgtatccactacaagaaattcagaatctcacagtcaagcttcagctgcaggctcttcagcaaaatgggtcttcagtgctctcagaagacaagagcaaacggttgaacac aattctaaatacaatgagcaccatctacagtactggaaaagtttgtaacccagataatccacaagaatgcttattacttgaaccaggtttgaatgaaataatggcaaacagtttagactacaatgagaggctctgggcttgggaaagctggagatctg aggtcggcaagcagctgaggccattatatgaagagtatgtggtcttgaaaaatgagatggcaagagcaaatcattatgaggactatggggattattggagaggagactatgaagtaaatggggtagatggctatgactacagccgcggccagttgattgaagatgtggaacatacctttgaagagattaaaccattatatgaacatcttcatgcctatgtgag ggcaaagttgatgaatgcctatccttcctatatcagtccaattggatgcctccctgctcatttgcttggtgatatgtggggtagattttggacaaatctgtactctttgacagttccctttggacagaaaccaaacatagatgttac tgatgcaatggtggaccaggcctgggatgcacagagaatattcaaggaggccgagaagttctttgtatctgttggtcttcctaatatgactcaaggattctgggaaaattccatgctaacggacccaggaaatgttcagaaagcagtctgccatcccacagcttgggacctggggaagggcgacttcaggatccttatgtgtgcaca aaggtgacaatggacgacttcctgacagctcatcatgagatggggcatatccagtatgatatggcatatgctgcacaaccttttctgctaagaaatggagctaatgaaggattccatgaagctgttggggaaatcatgtcactttctgcagccacacctaagcatt taaaatccattggtcttctgtcacccgattttcaagaagacaatgaaacagaaataaacttcctgctcaaacaagcactcacgattgttgggactctgccatttacttacatgttagagaagtggaggtggatggtctttaaaggggaaattcccaaagaccagtggatgaaaaaaagtggtgggagatgaagcgagatagttggggtggtgga acctgtgccccatgatgaaacatactgtgaccccgcatctctgttccatgtttctaatgattactcattcattcgatattacacaaggaccctttaccaattccagtttcaagaagcactttgtcaagcagctaaacatgaaggccctctgcacaa atgtgacatctcaaactctacagaagctggacagaaactgttcaatatgctgaggcttggaaaatcagaaccctggaccctagcattggaaaatgttgtaggagcaaagaacatgaatgtaaggccactgctcaactactttgagcccttatttacctggctgaaagaccagaacaagaagaattcttttgtggggatggagtaccgactggagtccatatgca gaccaaagcatcaaagtgaggataagcctaaaatcagctcttggagataaagcatatgaatggaacgacaatgaaatgtacctgttccgatcatctgttgcatatgctatgaggcagtactttttaaaagtaaaaaatcagatgattcttt ttggggaggaggatgtgcgagtggctaatttgaaaccaagaatctcctttaatttctttgtcactgcacctaaaaatgtgtctgatatcattcctagaactgaagttgaaaaggccatcaggatgtcccggagccgtatcaatgatgctttccgtctgaatgacaacagcctagagtttctggggatacagccaacacttggac ctcctaaccagccccctgtttccatatggctgattgtttttggagttgtgatggggagtgatagtggttggcattgtcatcctgatcttcactgggatcagagatcggaagaagaaaaataaagcaagaagtggagaaaatccttatgcctccatcgatattagcaa aggagaaaataatccaggattccaaaacactgatgatgttcagacctccttttagaacttgtttattgcagcttataatggttacaaataaagcaatagcatcacaaatttcacaaataaagcatttttttcactgcattctagttgtggtttgtccaaactcatcaatgtatcttaacgcgtgcgaagttcctattctctctaga aagtataggaacttcatcgataccgggtaggggaggcgcttttcccaaggcagtctggagcatgcgctttagcagccccgctgggcacttggcgctacacaagtggcctctggcctcgcacacattccacatcccccggtaggcgccaaccggctccgttctttgg tggccccttcgcgccaccttctactcctcccctagtcaggaagttcccccccgccccgcagctcgcgtcgtgcaggacgtgacaaatggaagtagcacgtctcactagtctcgtgcagatggacagcaccgctgagcaatggaagcgggtaggcctttggggcagcggccaatagcagctttgctcctt cgctttctgggctcagaggctgggaaggggtgggtccgggggcgggctcaggggcgggctcaggggcggggcgggcgcccgaaggtcctccggaggcccggcattctgcacgcttcaaaagcgcacgtctgccgcgctgttctcctcttcctcatctccgggcctttcgacctgcagccca agctagcttaccatgaccgagtacaagcccacggtgcgcctcgccacccgcgacgacgtccccagggccgtacgcaccctcgccgccgcgttcgccgactacccggccacgcgccacaccgtcgatccggaccgccacatcgagcgggtcaccgagctgcaagaactcttcctcacgcgcgtcgggct cgacatcggcaaggtgtgggtcgcggacgacggcgccgcggtggcggtctggaccacgccggagagcgtcgaagcgggggcggtgttcgccgagatcggcccgcgcatggccgagttgagcggttcccggctggccgcgcagcaacagatggaaggcctcctggcgccgcaccggcccaagga gcccgcgtggttcctggccaccgtcggcgtctcgcccgaccaccagggcaagggtctgggcagcgccgtcgtgctccccggagtggaggcggccgagcgcgccggggtgcccgccttcctggagacctccgcgccccgcaacctccccttctacgagcggctcggcttcaccgtcaccgccgac gtcgaggtgcccgaaggaccgcgcacctggtgcatgacccgcaagcccggtgcctgaggtacctctcatgctggagttcttcgcccaccccaacttgttattgcagcttataatggttacaaataaagcaatagcatcacaaatttcacaaaataaagcatttttttcactgcattctagttgtgtgg tttgtccaaactcatcaatgtatcttatcatcgatgaagttcctattctctagaaagtataggaacttctaacctcccgggtgacagataacttcgtataatgtatgctatacgaagttatgtcgacgcggcgcgccgaattataatactaacattactgaagaaaatgcccaaaagatggtaagttcttgaggctacccagggggtt attgattgcttcttaaagatcagaattactgcctataaaactggataaggaaatcatagagatctctcaagtgtgaggatgagtgactgcctctgtagctctgatcctagtctcccagatggctaaattcaattgaccttagagttcatctggaaaattgtta tgaatgaattatttgcccagattccaaagatgagtgaaaatgtttaataaagttgccatcactattctcattatatttggtatgtaaagcattcatggaaatgttctaagtcgttattgagccaataattttctttagcttataatgccaacaggtctatccgagaactacaaatgacatattaactgaaaatgcaactggggtttact gaaggcagcagcttagtaattaaggtaaccatggcttaggtgaaactggacctgggaattccttctttcattgacacagagctctgaggaatttccaaaggtcacagaagaaaagctataattaaactagtcccaaaaaatctcagcctactctgggaaa gcagcatattttgtttgacaagtgcaaggacttagaactttttttttctcactgatcctgaagtgccttttaagtatagttaagtggtggaaaattgagcaactatttaagaaaagactcttttttttcttccagcaatgctttccttcaaaacggtagcttcaaaacttcctgtcttttaaatgatcagggggct gtgtgtttaaattattgccattcatagaacagagtgggtctgaggatgcctgtttcctttgaaattctatgccccctcccagttttctaaaatttaagaaaccacagactttgacaatgtagttgccaaatgagttgcttttaactgctctaatagtttggtctt(seq id no:30)

The PCR identification results are shown in Figure 9. A total of 14 clones were identified, of which the ones marked with * are positive clones, and the PCR products are consistent with the sequencing results. The mouse embryonic stem cell clone with positive PCR results is a successfully edited humanized mouse embryonic stem cell model, but it still retains the PGK-Puro screening marker. Since there is a pair of frt sites in the same direction at both ends of PGK-Puro, it can be removed by FLP recombinase to solve the safety problem caused by transgenics.

The PGK-Puro screening marker is removed as follows:

Kit(Lonza，VPH-1001)小鼠胚胎干细胞电转试剂盒，使用A023程序，约2×10⁶个细胞被电穿孔，并且所述电转过程含有pPGK-FLPo质粒(Addgene，13793)的100μL电转缓冲液中进行。所述转染细胞被种到6个12孔板的孔中，3天后，采取玻璃拉针吸取单克隆的方式挑取小鼠胚胎干细胞克隆进96孔板中培养，第二天将单克隆消化传代一分为二，一份进行嘌呤霉素筛选，一份正常培养。若成功删除PGK-Puro抗性筛选标志，则嘌呤霉素筛选后细胞不耐受死亡。嘌呤霉素不耐受相对应的克隆可使用上游引物(hACE2-F：tgatagtggttggcattgt(SEQ ID NO:31))和下游引物(3arm-outR：tacagccaggatctggatgtcagc(SEQ ID NO:29))进行基因组基因型PCR鉴定。若成功删除PGK-Puro筛选标志，则PCR产物长度为1532bp，删除PGK-Puro前的PCR产物长度为2863bp。基因型鉴定结果如图9所示，跑胶条带在1500bp处的为成功删除PGK-puro后的克隆，条带在3000bp处的为删除前克隆。嘌呤霉素不耐受相对应的克隆则为最终成功编辑为人源化ACE2打靶的小鼠胚胎干细胞，也就是小鼠胚胎干细胞最终获得如图10所示的人源化ACE2基因。最终删除PGK-puro后小鼠胚胎干细胞Ace2位点基因组序列替换为SEQ ID NO:32，如下所示：The mouse embryonic stem cells with positive PCR results were further cultured in 6 cm dishes and electroporated using the Nucleofector ^TM IIs/2b electroporator and Mouse ES Cell

Kit (Lonza, VPH-1001) mouse embryonic stem cell electroporation kit, using the A023 program, about 2×10 ⁶ cells were electroporated, and the electroporation process was carried out in 100 μL electroporation buffer containing pPGK-FLPo plasmid (Addgene, 13793). The transfected cells were seeded into 6 wells of 12-well plates. After 3 days, the mouse embryonic stem cell clones were picked up by glass needle aspiration and cultured in 96-well plates. The next day, the monoclonal digestion and passage were divided into two, one for puromycin screening and one for normal culture. If the PGK-Puro resistance screening marker is successfully deleted, the cells will die due to intolerance after puromycin screening. The clones corresponding to puromycin intolerance can be identified by genomic genotype PCR using upstream primers (hACE2-F: tgatagtggttggcattgt (SEQ ID NO: 31)) and downstream primers (3arm-outR: tacagccaggatctggatgtcagc (SEQ ID NO: 29)). If the PGK-Puro screening marker is successfully deleted, the length of the PCR product is 1532bp, and the length of the PCR product before deleting PGK-Puro is 2863bp. The genotype identification results are shown in Figure 9. The band at 1500bp is the clone after the successful deletion of PGK-puro, and the band at 3000bp is the clone before deletion. The clone corresponding to puromycin intolerance is the mouse embryonic stem cell that was finally successfully edited to target humanized ACE2, that is, the mouse embryonic stem cell finally obtained the humanized ACE2 gene as shown in Figure 10. After the final deletion of PGK-puro, the genomic sequence of the mouse embryonic stem cell Ace2 site was replaced with SEQ ID NO:32, as shown below:

ccctatggagtggagaagagtcttataattttttaaatgggcagagaaatgaatttatttttaatttttagagacagggtttctttgtatagctctagctgtctttgattggtagacaaagctgtcctcaaactcagagatcttccttcctttgtctcctgagtgctgggattaaaggcatggaccaccactgccctgccccattctctccatta attttaagtgaatgcttgcaaaagctcacttctttggtgaacagcttcctttacaaataagtacctttgcct tcgtttttataggattcttaaaaagaaaaaaaagattcagccaggtggttgtggtgcacacctttaatcccagcagtcaggaggcagaggaaagcagatctcttgagtttgaggctagcctagtctacagagggagttccaggacagccaaggctacagagaggaactgtctaaaaacaccaagaaagagagaaaggaga gagggagaggatggatagcttattgatagaattgtcagaaaaggctataagttccaatatgtgtcccatgatttctaagtctagccc tttctgttatagtaaaatcatagtacaccctcctcctccagtgtatctttaacagcttttaaggaacatattaactaaatgtccaggttttgatttggccataaaatgttagcaaagctaaggttttctaggattaatgaataacatgtctttatttagtttacttaaaaaaatcattctaaaatatctgtttacatatctgtcctctc caggattaacttcatattggtccagcagcttgtttactgttctcttctgtttcttcttctgctttttttttcttctct tctcagtgcccaacccaagttcaaaggctgatgagagagaaaaactcatgaagagattttactctagggaaagttgctcagtggatgggatcttggcgcacggggaaagatgtcaagctcttcctggctccttctcagccttgttgctgtaactgctgctcagtccaccattgaggaacaggccaagacattttt ggacaagtttaaccacgaagccgaagacctgttctatcaaagttcacttgcttcttggaattataacaccaatattactgaagagaatgtcc aaaacatgaataatgctggggacaaatggtctgcctttttaaaggaacagtccacacttgcccaaatgtatccactacaagaaattcagaatctcacagtcaagcttcagctgcaggctcttcagcaaaaatgggtcttcagtgctctcagaagacaagagcaaacggttgaacacaattctaaatacaatgagcaccatctacagtactgg aaaagtttgtaacccagataatccacaagaatgcttattacttgaaccaggtttgaatgaaataatggcaaacagt ttagactacaatgagaggctctgggcttgggaaagctggagatctgaggtcggcaagcagctgaggccattatatgaagagtatgtggtcttgaaaaatgagatggcaagagcaaatcattatgaggactatggggattattggagaggagactatgaagtaaatggggtagatggctatgactacagccgcggccagttgattgaagatgtggaacatacctt tgaagagattaaaccattatatgaacatcttcatgcctatgtgagggcaaagttgatgaatgc ctatccttcctatatcagtccaattggatgcctccctgctcatttgcttggtgatatgtggggtagattttggacaaatctgtactctttgacagttccctttggacagaaaccaaacatagatgttatgatgcaatggtggaccaggcctgggatgcacagagaatattcaaggaggccgagaagttctttgtatctgt tggtcttcctaatatgactcaaggattctgggaaaattccatgctaacggacccaggaaatgttcagaaagcagtctgccatccca cagcttgggacctggggaagggcgacttcaggatccttatgtgcacaaaggtgacaatggacgacttcctgacagctcatcatgagatggggcatatccagtatgatatggcatatgctgcacaaccttttctgctaagaaatggagctaatgaaggattccatgaagctgttggggaaatcatgtcactttctgcagccacaccctaagcattta aaatccattggtcttctgtcacccgattttcaagaagacaatgaaacagaaataaacttcctgctcaaacaag cactcacgattgttgggactctgccatttacttacatgttagagaagtggaggtggatggtctttaaaggggaaattcccaaagaccagtggatgaaaaagtggtgggagatgaagcgagagatagttggggtggtggaacctgtgccccatgatgaaacatactgtgaccccgcatctctgttccatgttctaatgattactcattcattc gatattacacaaggaccctttaccaattccagtttcaagaagcactttgtcaagcagctaaacatgaaggcct ctgcacaaatgtgacatctcaaactctacagaagctggacagaaactgttcaatatgctgaggcttggaaaatcagaaccctggaccctagcattggaaaatgttgtaggagcaaagaacatgaatgtaaggccactgctcaactactttgagcccttatttacctggctgaaagaccagaacaagaattcttttgtgggatggagtaccgactgg agtccatatgcagaccaaagcatcaaagtgaggataagcctaaaatcagctcttggagataaagcatatga atggaacgacaatgaaatgtacctgttccgatcatctgttgcatatgctatgaggcagtactttttaaaagtaaaaatcagatgattctttttggggaggaggatgtgcgagtggctaatttgaaaccaagaatctcctttaatttctttgtcactgcacctaaaaatgtgtctgatatcattcctagaactgaagtt gaaaaggccatcaggatgtcccggagccgtatcaatgatgctttccgtctgaatgacaacagcctagagtttctggggatacagccaa cacttggacctcctaaccagccccctgtttccatatggctgattgtttttggagttgtgatggggagtgatagtggttggcattgtcatcctgatcttcactgggatcagagatcggaagaagaaaaataaagcaagaagtggagaaaatccttatgcctccatcgatattagcaaaggagaaaataatccaggattccaaaacact gatgatgttcagacctccttttagaacttgtttattgcagcttataatggttacaaataaagcaatagcatcacaaatttca caaataaagcatttttttcactgcattctagttgtggtttgtccaaactcatcaatgtatcttaacgcgtgcgaagttcctattctctgaaagtataggaacttctaacctcccgggtgacagataacttcgtataatgtatgctatacgaagttatgtcgacgcggcgcgccgaattataatactaacattactgaagaaaat gcccaaaagatggtaagttcttgaggctacccagggggttattgattgcttcttaaagatcagaattactgcctataaaact ggataaggaaatcatagagatctctcaagtgtgaggatgagtgactgcctctgtagctctgatcctagtctcccagatggctaaattcaattgaccttagagttcatctggaaaattgttatgaatgaattatttgcccagattccaaagatgagtgaaaatgtttaataaagttgccatcactattctcattatatttggtatgtaaagcattcat ggaaatgttctaagtcgttattgagccaataattttctttagcttataatgccaacaggtctatccgaga actacaaatgacatattaactgaaaaatgcaactggggtttactgaaggcagcagcttagtaattaaggtaaccatggcttaggtgaaactggacctgggaattccttctttcattgacacagagctctgaggaatttccaaaggtcacagaagaaaagctataattaaactagtcccaaaaaaatctcagcctactctgggaaagcagcatattttgtttga caagtgcaaggacttagaacttttttttttctcactgatcctgaagtgccttttaagtatagtta agtggtggaaaattgagcaactatttaagaaaagactctttttttcttcttccagcaatgctttccttcaaaacggtagcttcaaaacttcctgtcttttaaatgatcagggggctgtgtgtgtttaaattattgccattcatagaacagagtgggtctgaggatgcctgtttcctttgaaattctatgccccctcccag ttttctaaaatttaagaaaccacagagactttgacaatgtagttgccaaatgagttgcttttaactgctctaatagtttggtctt(seq id no:32)

Example 7 Formation of Humanized ACE2 Gene-Transformed Mice

1. Intraperitoneally inject 7.5 units of PMSG into 4-10 week old B6C3F1 female mice. 48 hours later, inject hCG and place them in a cage with CD1 male mice. The next morning, check the female mice for vaginal plugs and select the female mice with vaginal plugs. Record the corresponding fertilization time of the female mice.

2. The next day, the pregnant mice were euthanized by cervical dislocation, the abdomen of the mice was disinfected with 70% alcohol, and the abdominal skin and muscle layer were cut open with auxiliary forceps and ophthalmic scissors to open the abdominal cavity. The upper part of one uterine horn was grasped with forceps, and a small incision was made on the membrane near the fallopian tube with scissors, and the connection between the fallopian tube and the ovary was cut off. The fallopian tube and the attached uterus were moved to a 35 mm culture dish, and the fimbria of the fallopian tube was fixed with forceps. The flushing needle filled with M2 culture medium (Hogan, B. (1994). Manipulating the mouse embryo: a laboratory manual, 2nd edn (Cold Spring Harbor, NY, Cold Spring Harbor Laboratory Press).) was gently inserted into the fimbria, and the fallopian tube was flushed with 0.1 mL of M2 culture medium. The embryos flushed out were collected with an oviduct transfer tube and washed 3 times with M2 to collect E1.5 mouse 2-cell embryos.

3. The collected mouse embryos were placed in 0.3 M mannitol (Sigma-Aldrich Inc., St. Louis, MO) containing 0.1 mM MgSO4, _0.1 mM CaCl2 and 0.3% bovine serum albumin, and fused with 60 V 50 microseconds direct current using a Cellfusion CF-150/B electrofusion instrument and a 250-um fusion tank (BLS Ltd., Budapest, Hungary) to obtain quadruploid embryos; placed in KSOM medium (Summers, MC, McGinnis, LK, Lawtts, JA, Raffin, M., and Biggers, JD (2000). IVF of mouse ova in a simplex optimized medium supplemented with amino acids. Hum Reprod 15, 1791-1801.), after culturing in a CO2 incubator for 24 hours, the zona pellucida was removed with acidic Tyrode's solution (Sigma-Aldrich, T1788), and the cells were aggregated with embryonic stem cells (i.e., humanized ACE2 mouse embryonic stem cells prepared in the present application) to form chimeric embryos (Nagy, A., Rossant, J., Nagy, R., Abramow-Newerly, W., and Roder, JC (1993). Derivation of completely cell culture-derived mice from early-passage embryonic stem cells. Proc Natl Acad Sci USA 90, 8424-8428.).

4. Cultured overnight in a _CO2 incubator, transplanted into the uterus of a pseudo-pregnant mouse on day E2.5, and euthanized by cervical dislocation after 17 days, and then performed a laparotomy. The surrogate mice that were alive and breathing were placed in a suckling mouse cage and weaned after 21 days to obtain transgenic mice completely derived from embryonic stem cells, i.e., humanized ACE2 gene-modified mice (Figure 12).

The corresponding culture medium formula is shown in Table 7.

Table 7 Culture medium formula

Example 8 Verification of hACE2 expression in humanized ACE2 gene-modified mice

Small intestine, lung and kidney samples of a wild-type mouse and a humanized ACE2 gene-modified mouse (prepared in Example 7) were taken for RNA extraction and qPCR verification of hACE2 gene expression. Tissue samples were lysed by adding Trizol reagent. 200 μl of chloroform was added to each milliliter of Trizol lysate, and the mixture was allowed to stand until stratification after vigorous shaking. After repeating the operation 3 times, centrifuged at 4°C, 14000rpm for 15min, and 400 μl of the supernatant was added to 400 μl of pre-cooled isopropanol, inverted and mixed, and allowed to stand on ice for 5min. Centrifuged at 4°C, 14000pm for 10min, a white precipitate was visible at the bottom of the EP tube, which was RNA.

Discard the supernatant, add pre-cooled 70% ethanol solution, wash once, centrifuge, remove ethanol, dry RNA until colorless and transparent, add appropriate amount of RNase-free H2O according to the amount of precipitation, and bathe in 60℃ water until completely dissolved. Take 1μl respectively, dilute 50 times with 10mMTris-HCl (pH 7.5) and H2O to determine the purity and concentration, and the OD260/280 value is about 2.0. The extracted RNA is stored at -80℃ for long-term storage.

2 μg RNA was taken for inversion, and the system is shown in Table 8. After the cDNA sample obtained by inversion was diluted 30 times, it was further used for fluorescence quantitative PCR to detect gene expression. The hACE2 detection qPCR primers are as follows (hACE2-qF: GGTCTTCAGTGCTCTCAG (SEQ ID NO: 33); hACE2-qR: GCATTCTTGTGGATTATCTGG (SEQ ID NO: 34)), and it can be seen that the humanized ACE2 gene-modified mice express human ACE2 at the RNA level and have tissue specificity (Figure 13).

Table 8

In addition, the small intestine, lung and testicular tissues of humanized ACE2 gene-modified mice were taken for immunofluorescence tissue protein level verification of human ACE2 expression. Mouse tissues were fixed in 4% PFA at 4°C overnight. The next day, the tissues were rinsed 3 times in PBS and cryoprotected in 30% sucrose in PBS at 4°C overnight. The tissues were then incubated in a 1:1 mixture of 30% sucrose/PBS and O.C.T. for 2-4 hours. Frozen embedding medium (Sakura, catalog number 4583). Next, the tissues were transferred from the sucrose/OCT mixture to a cryogenic mold and filled with O.C.T. The embedded tissues were frozen on dry ice and then stored at -80°C until cryostat sectioning. The frozen organoid tissues were cut into 20 μm slices using a cryostat and collected on superfrost Ultra Plus slides. The sections were dried overnight and then used for immunofluorescence. At room temperature, 4% PFA was directly post-fixed on the slide for 10 minutes, and then washed 3x10 times in PBS. The outline of the tissue area was outlined using a hydrophobic PAP pen. Blocked with 5% BSA/0.3% TX100 in PBS containing 0.05% sodium azide and incubated at room temperature for 30 minutes. The tissue was then incubated with anti-ACE2 antibody (ET1611-58, Huabio) at 4°C overnight. After washing with PBS, the secondary antibody (A11004, Invitrogen) was incubated for 1 hour, and then DAPI for 2 minutes. Finally, the coverslip was mounted on a slide for observation, and it can be seen from the tissue immunofluorescence results that human ACE2 is specifically expressed in humanized ACE2 genetically modified mouse tissues at the protein expression level (Figure 14).

Example 9 SARS-CoV-2 infection of humanized ACE2 genetically modified mice

Probe One-step qRT-PCR Kit(Toyobo)试剂盒对SARS-CoV-2的核蛋白N基因进行检测。荧光定量PCR检测所用到的引物如下：正向引物：5’-GGGGAACTTCTCCTGCTAGAAT-3’(SEQ IDNO:35)；反向引物:5’-CAGACATTTTGCTCTCAAGCTG-3’(SEQ ID NO:36)，TaqMan探针序列为5’-FAM-TTGCTGCTGCTTGACAGATT-TAMRA-3’(SEQ ID NO:37)，结果可见人源化ACE2基因改造小鼠经SARS-CoV-2感染后肺、气道及小肠在D1、D3病毒载量达到顶峰，随之下降，表明本发明人源化ACE2基因改造小鼠对SARS-CoV-2易感(图15)，而对照组小鼠并未检测到病毒。图15中的折线表示平均值。The humanized ACE2 gene-modified mice inhaled 30 μl of DMEM containing 2×10 ⁶ TCID ₅₀ viral load of SARS-CoV-2 through nasal drops, while the control group was dripped with 30 μl of DMEM. The lung, airway and small intestinal tissues of the infected mice were taken on D1, D3, D5, D6, D7 and D9, and RNA was extracted and fluorescent quantitative PCR was used to detect the SARS-CoV-2 virus titer. The RNA extraction method was consistent with the above-mentioned hACE2 expression detection example. The extracted tissue RNA was used

The Probe One-step qRT-PCR Kit (Toyobo) was used to detect the nucleoprotein N gene of SARS-CoV-2. The primers used for the fluorescence quantitative PCR test are as follows: forward primer: 5'-GGGGAACTTCTCCTGCTAGAAT-3' (SEQ ID NO: 35); reverse primer: 5'-CAGACATTTTGCTCTCAAGCTG-3' (SEQ ID NO: 36), and the TaqMan probe sequence is 5'-FAM-TTGCTGCTGCTTGACAGATT-TAMRA-3' (SEQ ID NO: 37). The results show that the humanized ACE2 gene-modified mice were infected with SARS-CoV-2. The lung, airway and small intestine reached a peak viral load on D1 and D3, and then decreased, indicating that the humanized ACE2 gene-modified mice of the present invention are susceptible to SARS-CoV-2 (Figure 15), while the control group mice did not detect the virus. The broken line in Figure 15 represents the average value.

Sequence Listing

<110> Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences

<120> Preparation method and application of humanized ACE2 gene-modified mouse embryonic stem cell model

<150> 202010152182.X

<151> 2020-03-06

<160> 37

<170> SIPOSequenceListing 1.0

<210> 1

<211> 23

<212> DNA

<213> Natural sequence

<220>

<223> sgRNA1 sequence

<400> 1

tactgctcag tccctcaccg agg 23

<210> 2

<211> 23

<212> DNA

<213> Natural sequence

<220>

<223> sgRNA2 sequence

<400> 2

cttggcattt tcctcggtga ggg 23

<210> 3

<211> 23

<212> DNA

<213> Natural sequence

<220>

<223> sgRNRA3 sequence

<400> 3

caagtgaactttgataagac agg 23

<210> 4

<211> 25

<212> DNA

<213> Artificial Sequence

<220>

<223> Synthesize the upstream single-stranded primer sequence of sgRNA2

<400> 4

caccgcttgg cattttcctc ggtga 25

<210> 5

<211> 25

<212> DNA

<213> Artificial Sequence

<220>

<223> Synthesize the downstream single-stranded primer sequence of sgRNA2

<400> 5

aaactcaccg aggaaaatgc caagc 25

<210> 6

<211> 25

<212> DNA

<213> Artificial Sequence

<220>

<223> Synthesize the upstream single-stranded primer sequence of sgRNA1

<400> 6

caccgtactg ctcagtccct caccg 25

<210> 7

<211> 25

<212> DNA

<213> Artificial Sequence

<220>

<223> Synthesize the downstream single-stranded primer sequence of sgRNA1

<400> 7

aaaccggtga gggactgagc agtac 25

<210> 8

<211> 25

<212> DNA

<213> Artificial Sequence

<220>

<223> Synthesize the upstream single-stranded primer sequence of sgRNA3

<400> 8

caccgcaagt gaactttgat aagac 25

<210> 9

<211> 25

<212> DNA

<213> Artificial Sequence

<220>

<223> Synthesize the downstream single-stranded primer sequence of sgRNA3

<400> 9

aaacgtctta tcaaagttca cttgc 25

<210> 10

<211> 28

<212> DNA

<213> Natural sequence

<220>

<223> 5arm-sgF

<400> 10

ggttttgatt tggccataaa atgttagc 28

<210> 11

<211> 25

<212> DNA

<213> Natural sequence

<220>

<223> 3arm-sgR

<400> 11

attcccaggt ccagtttcac ctaag 25

<210> 12

<211> 2418

<212> DNA

<213> Natural sequence

<220>

<223> hACE2-CDS sequence

<400> 12

atgtcaagct cttcctggct ccttctcagc cttgttgctg taactgctgc tcagtccacc 60

attgaggaac aggccaagac atttttggac aagtttaacc acgaagccga agacctgttc 120

tatcaaagtt cacttgcttc ttggaattat aacaccaata ttactgaaga gaatgtccaa 180

aacatgaata atgctgggga caaatggtct gcctttttaa aggaacagtc cacacttgcc 240

caaatgtatc cactacaaga aattcagaat ctcacagtca agcttcagct gcaggctctt 300

cagcaaaatg ggtcttcagt gctctcagaa gacaagagca aacggttgaa cacaattcta 360

aatacaatga gcaccatcta cagtactgga aaagtttgta acccagataa tccacaagaa 420

tgcttattac ttgaaccagg tttgaatgaa ataatggcaa acagtttaga ctacaatgag 480

aggctctggg cttgggaaag ctggagatct gaggtcggca agcagctgag gccattatat 540

gaagagtatg tggtcttgaa aaatgagatg gcaagagcaa atcattatga ggactatggg 600

gattattgga gaggagacta tgaagtaaat ggggtagatg gctatgacta cagccgcggc 660

cagttgattg aagatgtgga acataccttt gaagagatta aaccattata tgaacatctt 720

catgcctatg tgagggcaaa gttgatgaat gcctatcctt cctatatcag tccaattgga 780

tgcctccctg ctcatttgct tggtgatatg tggggtagat tttggacaaa tctgtactct 840

ttgacagttc cctttggaca gaaaccaaac atagatgtta ctgatgcaat ggtggaccag 900

gcctgggatg cacagagaat attcaaggag gccgagaagt tctttgtatc tgttggtctt 960

cctaatatga ctcaaggatt ctgggaaaat tccatgctaa cggacccagg aaatgttcag 1020

aaagcagtct gccatcccac agcttgggac ctggggaagg gcgacttcag gatccttatg 1080

tgcacaaagg tgacaatgga cgacttcctg acagctcatc atgagatggg gcatatccag 1140

tatgatatgg catatgctgc acaacctttt ctgctaagaa atggagctaa tgaaggattc 1200

catgaagctg ttggggaaat catgtcactt tctgcagcca cacctaagca tttaaaatcc 1260

attggtcttc tgtcacccga ttttcaagaa gacaatgaaa cagaaataaa cttcctgctc 1320

aaacaagcac tcacgattgt tgggactctg ccatttactt acatgttaga gaagtggagg 1380

tggatggtct ttaaagggga aattcccaaa gaccagtgga tgaaaaagtg gtgggatg 1440

aagcgagaga tagttggggt ggtggaacct gtgccccatg atgaaacata ctgtgacccc 1500

gcatctctgt tccatgtttc taatgattac tcattcattc gatattacac aaggaccctt 1560

taccaattcc agtttcaaga agcactttgt caagcagcta aacatgaagg ccctctgcac 1620

aaatgtgaca tctcaaactc tacagaagct ggacagaaac tgttcaatat gctgaggctt 1680

ggaaaatcag aaccctggac cctagcattg gaaaatgttg taggagcaaa gaacatgaat 1740

gtaaggccac tgctcaacta ctttgagccc ttatttacct ggctgaaaga ccagaacaag 1800

aattcttttg tgggatggag taccgactgg agtccatatg cagaccaaag catcaaagtg 1860

aggataagcc taaaatcagc tcttggagat aaagcatatg aatggaacga caatgaaatg 1920

tacctgttcc gatcatctgt tgcatatgct atgaggcagt actttttaaa agtaaaaaat 1980

cagatgattc tttttgggga ggaggatgtg cgagtggcta atttgaaacc aagaatctcc 2040

tttaatttct ttgtcactgc acctaaaaat gtgtctgata tcattcctag aactgaagtt 2100

gaaaaggcca tcaggatgtc ccggagccgt atcaatgatg ctttccgtct gaatgacaac 2160

agcctagagt ttctggggat acagccaaca cttggacctc ctaaccagcc ccctgtttcc 2220

atatggctga ttgtttttgg agttgtgatg ggagtgatag tggttggcat tgtcatcctg 2280

atcttcactg ggatcagaga tcggaagaag aaaaataaag caagaagtgg agaaaatcct 2340

tatgcctcca tcgatattag caaaggagaa aataatccag gattccaaaa cactgatgat 2400

gttcagacctccttttag 2418

<210> 13

<211> 805

<212> PRT

<213> Natural sequence

<220>

<223> hACE2-protein sequence

<400> 13

Met Ser Ser Ser Ser Trp Leu Leu Leu Ser Leu Val Ala Val Thr Ala

1 5 10 15

Ala Gln Ser Thr Ile Glu Glu Gln Ala Lys Thr Phe Leu Asp Lys Phe

20 25 30

Asn His Glu Ala Glu Asp Leu Phe Tyr Gln Ser Ser Leu Ala Ser Trp

35 40 45

Asn Tyr Asn Thr Asn Ile Thr Glu Glu Asn Val Gln Asn Met Asn Asn

50 55 60

Ala Gly Asp Lys Trp Ser Ala Phe Leu Lys Glu Gln Ser Thr Leu Ala

65 70 75 80

Gln Met Tyr Pro Leu Gln Glu Ile Gln Asn Leu Thr Val Lys Leu Gln

85 90 95

Leu Gln Ala Leu Gln Gln Asn Gly Ser Ser Val Leu Ser Glu Asp Lys

100 105 110

Ser Lys Arg Leu Asn Thr Ile Leu Asn Thr Met Ser Thr Ile Tyr Ser

115 120 125

Thr Gly Lys Val Cys Asn Pro Asp Asn Pro Gln Glu Cys Leu Leu Leu

130 135 140

Glu Pro Gly Leu Asn Glu Ile Met Ala Asn Ser Leu Asp Tyr Asn Glu

145 150 155 160

Arg Leu Trp Ala Trp Glu Ser Trp Arg Ser Glu Val Gly Lys Gln Leu

165 170 175

Arg Pro Leu Tyr Glu Glu Tyr Val Val Leu Lys Asn Glu Met Ala Arg

180 185 190

Ala Asn His Tyr Glu Asp Tyr Gly Asp Tyr Trp Arg Gly Asp Tyr Glu

195 200 205

Val Asn Gly Val Asp Gly Tyr Asp Tyr Ser Arg Gly Gln Leu Ile Glu

210 215 220

Asp Val Glu His Thr Phe Glu Glu Ile Lys Pro Leu Tyr Glu His Leu

225 230 235 240

His Ala Tyr Val Arg Ala Lys Leu Met Asn Ala Tyr Pro Ser Tyr Ile

245 250 255

Ser Pro Ile Gly Cys Leu Pro Ala His Leu Leu Gly Asp Met Trp Gly

260 265 270

Arg Phe Trp Thr Asn Leu Tyr Ser Leu Thr Val Pro Phe Gly Gln Lys

275 280 285

Pro Asn Ile Asp Val Thr Asp Ala Met Val Asp Gln Ala Trp Asp Ala

290 295 300

Gln Arg Ile Phe Lys Glu Ala Glu Lys Phe Phe Val Ser Val Gly Leu

305 310 315 320

Pro Asn Met Thr Gln Gly Phe Trp Glu Asn Ser Met Leu Thr Asp Pro

325 330 335

Gly Asn Val Gln Lys Ala Val Cys His Pro Thr Ala Trp Asp Leu Gly

340 345 350

Lys Gly Asp Phe Arg Ile Leu Met Cys Thr Lys Val Thr Met Asp Asp

355 360 365

Phe Leu Thr Ala His His Glu Met Gly His Ile Gln Tyr Asp Met Ala

370 375 380

Tyr Ala Ala Gln Pro Phe Leu Leu Arg Asn Gly Ala Asn Glu Gly Phe

385 390 395 400

His Glu Ala Val Gly Glu Ile Met Ser Leu Ser Ala Ala Thr Pro Lys

405 410 415

His Leu Lys Ser Ile Gly Leu Leu Ser Pro Asp Phe Gln Glu Asp Asn

420 425 430

Glu Thr Glu Ile Asn Phe Leu Leu Lys Gln Ala Leu Thr Ile Val Gly

435 440 445

Thr Leu Pro Phe Thr Tyr Met Leu Glu Lys Trp Arg Trp Met Val Phe

450 455 460

Lys Gly Glu Ile Pro Lys Asp Gln Trp Met Lys Lys Trp Trp Glu Met

465 470 475 480

Lys Arg Glu Ile Val Gly Val Val Glu Pro Val Pro His Asp Glu Thr

485 490 495

Tyr Cys Asp Pro Ala Ser Leu Phe His Val Ser Asn Asp Tyr Ser Phe

500 505 510

Ile Arg Tyr Tyr Thr Arg Thr Leu Tyr Gln Phe Gln Phe Gln Glu Ala

515 520 525

Leu Cys Gln Ala Ala Lys His Glu Gly Pro Leu His Lys Cys Asp Ile

530 535 540

Ser Asn Ser Thr Glu Ala Gly Gln Lys Leu Phe Asn Met Leu Arg Leu

545 550 555 560

Gly Lys Ser Glu Pro Trp Thr Leu Ala Leu Glu Asn Val Val Gly Ala

565 570 575

Lys Asn Met Asn Val Arg Pro Leu Leu Asn Tyr Phe Glu Pro Leu Phe

580 585 590

Thr Trp Leu Lys Asp Gln Asn Lys Asn Ser Phe Val Gly Trp Ser Thr

595 600 605

Asp Trp Ser Pro Tyr Ala Asp Gln Ser Ile Lys Val Arg Ile Ser Leu

610 615 620

Lys Ser Ala Leu Gly Asp Lys Ala Tyr Glu Trp Asn Asp Asn Glu Met

625 630 635 640

Tyr Leu Phe Arg Ser Ser Val Ala Tyr Ala Met Arg Gln Tyr Phe Leu

645 650 655

Lys Val Lys Asn Gln Met Ile Leu Phe Gly Glu Glu Asp Val Arg Val

660 665 670

Ala Asn Leu Lys Pro Arg Ile Ser Phe Asn Phe Phe Val Thr Ala Pro

675 680 685

Lys Asn Val Ser Asp Ile Ile Pro Arg Thr Glu Val Glu Lys Ala Ile

690 695 700

Arg Met Ser Arg Ser Arg Ile Asn Asp Ala Phe Arg Leu Asn Asp Asn

705 710 715 720

Ser Leu Glu Phe Leu Gly Ile Gln Pro Thr Leu Gly Pro Pro Asn Gln

725 730 735

Pro Pro Val Ser Ile Trp Leu Ile Val Phe Gly Val Val Met Gly Val

740 745 750

Ile Val Val Gly Ile Val Ile Leu Ile Phe Thr Gly Ile Arg Asp Arg

755 760 765

Lys Lys Lys Asn Lys Ala Arg Ser Gly Glu Asn Pro Tyr Ala Ser Ile

770 775 780

Asp Ile Ser Lys Gly Glu Asn Asn Pro Gly Phe Gln Asn Thr Asp Asp

785 790 795 800

Val Gln Thr Ser Phe

805

<210> 14

<211> 122

<212> DNA

<213> Natural sequence

<220>

<223> SV40 polyA sequence

<400> 14

aacttgttta ttgcagctta taatggttac aaataaagca atagcatcac aaatttcaca 60

aataaagcat ttttttcact gcattctagt tgtggtttgt ccaaactcat caatgtatct 120

ta 122

<210> 15

<211> 970

<212> DNA

<213> Natural sequence

<220>

<223> 5' homology arm sequence

<400> 15

ccctatggag tggagaagag tcttataatt ttttaaatgg gcagagaaat gaatttattt 60

ttaattttta gagacagggt ttctttgtat agctctagct gtctttgatt ggtagacaaa 120

gctgtcctca aactcagaga tcttccttcc tttgtctcct gagtgctggg attaaaggca 180

tggaccacca ctgccctgcc ccattctctc cattaatttt aagtgaatgc ttgcaaaagc 240

tcacttcttt ggtgaacagc ttcctttaca aataagtacc tttgccttcg tttttatagg 300

attcttaaaa agaaaaaaaa gattcagcca ggtggttgtg gtgcacacct ttaatcccag 360

cagtcaggag gcagaggaaa gcagatctct tgagtttgag gctagcctag tctacagagg 420

gagttccagg acagccaagg ctacagagag gaactgtcta aaaacaccaa gaaagagaga 480

aaggagagag ggagaggatg gatagctttat tgatagaatt gtcagaaaag gctataagtt 540

ccaatatgtg tcccatgatt tctaagtcta gccctttctg ttatagtaaa atcatagtac 600

accctcctcc tccagtgtat ctttaacagc ttttaaggaa catattaact aaatgtccag 660

gttttgattt ggccataaaa tgttagcaaa gctaaggttt tctaggatta atgaataaca 720

tgtctttatt tagtttactt aaaaaaatca ttctaaaata tctgtttaca tatctgtcct 780

ctccaggatt aacttcatat tggtccagca gcttgtttac tgttctcttc tgtttcttct 840

tctgcttttt ttttcttctc ttctcagtgc ccaacccaag ttcaaaggct gatgagagag 900

aaaaactcat gaagagattt tactctaggg aaagttgctc agtggatggg atcttggcgc 960

acggggaaag 970

<210> 16

<211> 971

<212> DNA

<213> Natural sequence

<220>

<223> 3’ homology arm sequence

<400> 16

gaattataat actaacatta ctgaagaaaa tgcccaaaag atggtaagtt cttgaggcta 60

cccagggggt tattgattgc ttcttaaaga tcagaattac tgcctataaa actggataag 120

gaaatcatag agatctctca agtgtgagga tgagtgactg cctctgtagc tctgatccta 180

gtctcccaga tggctaaatt caattgacct tagagttcat ctggaaaatt gttatgaatg 240

aattatttgc ccagattcca aagatgagtg aaaatgttta ataaagttgc catcactatt 300

ctcattatat ttggtatgta aagcattcat ggaaatgttc taagtcgtta ttgagccaat 360

aattttcttt agcttataat gccaacaggt ctatccgaga actacaaatg acatattaac 420

tgaaaaatgc aactggggtt tactgaaggc agcagcttag taattaaggt aaccatggct 480

taggtgaaac tggacctggg aattccttct ttcattgaca cagagctctg aggaatttcc 540

aaaggtcaca gaagaaaagc tataattaaa ctagtcccaa aaaatctcag cctactctgg 600

gaaagcagca tattttgttt gacaagtgca aggacttaga actttttttt ttctcactga 660

tcctgaagtg ccttttaagt atagttaagt ggtggaaaat tgagcaacta tttaagaaaa 720

gactcttttt tttcttcttc cagcaatgct ttccttcaaa acggtagctt caaaacttcc 780

tgtcttttaa atgatcaggg ggctgtgtgt ttaaattatt gccattcata gaacagagtg 840

ggtctgagga tgcctgtttc ctttgaaatt ctatgccccc tcccagtttt ctaaaattta 900

agaaaccaca gagactttga caatgtagtt gccaaatgag ttgcttttaa ctgctctaat 960

agtttggtct t 971

<210> 17

<211> 1124

<212> DNA

<213> Natural sequence

<220>

<223> PGK-puro sequence

<400> 17

gggtagggga ggcgcttttc ccaaggcagt ctggagcatg cgctttagca gccccgctgg 60

gcacttggcg ctacacaagt ggcctctggc ctcgcacaca ttccacatcc cccggtaggc 120

gccaaccggc tccgttcttt ggtggcccct tcgcgccacc ttctactcct cccctagtca 180

ggaagttccc ccccgccccg cagctcgcgt cgtgcaggac gtgacaaatg gaagtagcac 240

gtctcactag tctcgtgcag atggacagca ccgctgagca atggaagcgg gtaggccttt 300

ggggcagcgg ccaatagcag ctttgctcct tcgctttctg ggctcagagg ctgggaaggg 360

gtgggtccgg gggcgggctc aggggcgggc tcaggggcgg ggcgggcgcc cgaaggtcct 420

ccggaggccc ggcattctgc acgcttcaaa agcgcacgtc tgccgcgctg ttctcctctt 480

cctcatctcc gggcctttcg acctgcagcc caagctagct taccatgacc gagtacaagc 540

ccacggtgcg cctcgccacc cgcgacgacg tccccagggc cgtacgcacc ctcgccgccg 600

cgttcgccga ctaccccgcc acgcgccaca ccgtcgatcc ggaccgccac atcgagcggg 660

tcaccgagct gcaagaactc ttcctcacgc gcgtcgggct cgacatcggc aaggtgtggg 720

tcgcggacga cggcgccgcg gtggcggtct ggaccacgcc ggagagcgtc gaagcggggg 780

cggtgttcgc cgagatcggc ccgcgcatgg ccgagttgag cggttcccgg ctggccgcgc 840

agcaacagat ggaaggcctc ctggcgccgc accggcccaa ggagcccgcg tggttcctgg 900

ccaccgtcgg cgtctcgccc gaccaccagg gcaagggtct gggcagcgcc gtcgtgctcc 960

ccggagtgga ggcggccgag cgcgccgggg tgcccgcctt cctggagacc tccgcgcccc 1020

gcaacctccc cttctacgag cggctcggct tcaccgtcac cgccgacgtc gaggtgcccg 1080

aaggaccgcg cacctggtgc atgacccgca agcccggtgc ctga 1124

<210> 18

<211> 34

<212> DNA

<213> Natural sequence

<220>

<223> Frt sequence

<400> 18

gaagttccta ttctctagaa agtataggaa cttc 34

<210> 19

<211> 50

<212> DNA

<213> Artificial Sequence

<220>

<223> 5arm-pcrF

<400> 19

tcgcacacat tccacatcca ccggtcccta tggagtggag aagagtctta 50

<210> 20

<211> 47

<212> DNA

<213> Artificial Sequence

<220>

<223> 5arm-pcrR

<400> 20

gaaggagcca ggaagagctt gacatctttc cccgtgcgcc aagatcc 47

<210> 21

<211> 47

<212> DNA

<213> Artificial Sequence

<220>

<223> hACE2-F

<400> 21

ggatcttggc gcacggggaa agatgtcaag ctcttcctgg ctccttc 47

<210> 22

<211> 49

<212> DNA

<213> Artificial Sequence

<220>

<223> hACE2-R

<400> 22

cattataagc tgcaataaac aagttctaaa aggaggtctg aacatcatc 49

<210> 23

<211> 49

<212> DNA

<213> Artificial Sequence

<220>

<223> SV40-F

<400> 23

gatgatgttc agacctcctt ttagaacttg tttattgcag cttataatg 49

<210> 24

<211> 48

<212> DNA

<213> Artificial Sequence

<220>

<223> SV40-R

<400> 24

agagaatagg aacttcgcac gcgttaagat acattgatga gtttggac 48

<210> 25

<211> 50

<212> DNA

<213> Artificial Sequence

<220>

<223> 3arm-pcrF

<400> 25

tacgaagtta tgtcgacgcg gcgcgccgaa ttataatact aacattactg 50

<210> 26

<211> 53

<212> DNA

<213> Artificial Sequence

<220>

<223> 3arm-pcrR

<400> 26

tatgaccatg attacgccaa gcttaagacc aaactattag agcagttaaa agc 53

<210> 27

<211> 8470

<212> DNA

<213> Artificial Sequence

<220>

<223> Targeting vector sequence

<400> 27

tcgcgcgttt cggtgatgac ggtgaaaacc tctgacacat gcagctcccg gagacggtca 60

cagcttgtct gtaagcggat gccgggagca gacaagcccg tcagggcgcg tcagcgggtg 120

ttggcgggtg tcggggctgg cttaactatg cggcatcaga gcagattgta ctgagagtgc 180

accatatgta ccgggtaggg gaggcgcttt tcccaaggca gtctggagca tgcgctttag 240

cagccccgct gggcacttgg cgctacacaa gtggcctctg gcctcgcaca cattccacat 300

ccaccggtcc ctatggagtg gagaagagtc ttataatttt ttaaatgggc agagaaatga 360

atttattttt aatttttaga gacagggttt ctttgtatag ctctagctgt ctttgattgg 420

tagacaaagc tgtcctcaaa ctcagagatc ttccttcctt tgtctcctga gtgctgggat 480

taaaggcatg gaccaccact gccctgcccc attctctcca ttaattttaa gtgaatgctt 540

gcaaaagctc acttctttgg tgaacagctt cctttacaaa taagtacctt tgccttcgtt 600

tttataggat tcttaaaaag aaaaaaaaga ttcagccagg tggttgtggt gcacaccttt 660

aatcccagca gtcaggaggc agaggaaagc agatctcttg agtttgaggc tagcctagtc 720

tacagaggga gttccaggac agccaaggct acagagagga actgtctaaa aacaccaaga 780

aagagagaaa ggagagagggg agaggatgga tagcttattg atagaattgt cagaaaaggc 840

tataagttcc aatatgtgtc ccatgatttc taagtctagc cctttctgtt atagtaaaat 900

catagtacac cctcctcctc cagtgtatct ttaacagctt ttaaggaaca tattaactaa 960

atgtccaggt tttgatttgg ccataaaatg ttagcaaagc taaggttttc taggattaat 1020

gaataacatg tctttattta gtttacttaa aaaaatcatt ctaaaatatc tgtttacata 1080

tctgtcctct ccaggattaa cttcatattg gtccagcagc ttgtttactg ttctcttctg 1140

tttcttcttc tgcttttttt ttcttctctt ctcagtgccc aacccaagtt caaaggctga 1200

tgagagagaa aaactcatga agagatttta ctctagggaa agttgctcag tggatgggat 1260

cttggcgcac ggggaaagat gtcaagctct tcctggctcc ttctcagcct tgttgctgta 1320

actgctgctc agtccaccat tgaggaacag gccaagacat ttttggacaa gtttaaccac 1380

gaagccgaag acctgttcta tcaaagttca cttgcttctt ggaattataa caccaatatt 1440

actgaagaga atgtccaaaa catgaataat gctggggaca aatggtctgc ctttttaaag 1500

gaacagtcca cacttgccca aatgtatcca ctacaagaaa ttcagaatct cacagtcaag 1560

cttcagctgc aggctcttca gcaaaatggg tcttcagtgc tctcagaaga caagagcaaa 1620

cggttgaaca caattctaaa tacaatgagc accatctaca gtactggaaa agtttgtaac 1680

ccagataatc cacaagaatg cttattactt gaaccaggtt tgaatgaaat aatggcaaac 1740

agtttagact acaatgagag gctctgggct tgggaaagct ggagatctga ggtcggcaag 1800

cagctgaggc cattatatga agagtatgtg gtcttgaaaa atgagatggc aagagcaaat 1860

cattatgagg actatgggga ttatggaga ggagactatg aagtaaatgg ggtagatggc 1920

tatgactaca gccgcggcca gttgattgaa gatgtggaac atacctttga agagattaaa 1980

ccattatatg aacatcttca tgcctatgtg agggcaaagt tgatgaatgc ctatccttcc 2040

tatatcagtc caattggatg cctccctgct catttgcttg gtgatatgtg gggtagattt 2100

tggacaaatc tgtactcttt gacagttccc tttggacaga aaccaaacat agatgttatact 2160

gatgcaatgg tggaccaggc ctgggatgca cagagaatat tcaaggaggc cgagaagttc 2220

tttgtatctg ttggtcttcc taatatgact caaggattct gggaaaattc catgctaacg 2280

gacccaggaa atgttcagaa agcagtctgc catcccacag cttggggacct ggggaagggc 2340

gacttcagga tccttatgtg cacaaaggtg acaatggacg acttcctgac agctcatcat 2400

gagatggggc atatccagta tgatatggca tatgctgcac aaccttttct gctaagaaat 2460

ggagctaatg aaggattcca tgaagctgtt ggggaaatca tgtcactttc tgcagccaca 2520

cctaagcatt taaaatccat tggtcttctg tcacccgatt ttcaagaaga caatgaaaca 2580

gaaataaact tcctgctcaa acaagcactc acgattgttg ggactctgcc atttacttac 2640

atgttagaga agtggaggtg gatggtcttt aaaggggaaa ttcccaaaga ccagtggatg 2700

aaaaagtggt gggagatgaa gcgagagata gttggggtgg tggaacctgt gccccatgat 2760

gaaacatact gtgaccccgc atctctgttc catgtttcta atgattactc attcattcga 2820

tattacacaa ggacccttta ccaattccag tttcaagaag cactttgtca agcagctaaa 2880

catgaaggcc ctctgcacaa atgtgacatc tcaaactcta cagaagctgg acagaaactg 2940

ttcaatatgc tgaggcttgg aaaatcagaa ccctggaccc tagcattgga aaatgttgta 3000

ggagcaaaga acatgaatgt aaggccactg ctcaactact ttgagccctt atttacctgg 3060

ctgaaagacc agaacaagaa ttcttttgtg ggatggagta ccgactggag tccatatgca 3120

gaccaaagca tcaaagtgag gataagccta aaatcagctc ttggagataa agcatatgaa 3180

tggaacgaca atgaaatgta cctgttccga tcatctgttg catatgctat gaggcagtac 3240

tttttaaaag taaaaaatca gatgattctt tttggggagg aggatgtgcg agtggctaat 3300

ttgaaaccaa gaatctcctt taatttcttt gtcactgcac ctaaaaatgt gtctgatatc 3360

attcctagaa ctgaagttga aaaggccatc aggatgtccc ggagccgtat caatgatgct 3420

ttccgtctga atgacaacag cctagagttt ctggggatac agccaacact tggacctcct 3480

aaccagcccc ctgtttccat atggctgatt gtttttggag ttgtgatggg agtgatagtg 3540

gttggcattg tcatcctgat cttcactggg atcagagatc ggaagaagaa aaataaagca 3600

agaagtggag aaaatcctta tgcctccatc gatattagca aaggagaaaa taatccagga 3660

ttccaaaaca ctgatgatgt tcagacctcc ttttagaact tgtttatattgc agcttataat 3720

ggttacaaat aaagcaatag catcacaaat ttcacaaata aagcattttt ttcactgcat 3780

tctagttgtg gtttgtccaa actcatcaat gtatcttaac gcgtgcgaag ttcctattct 3840

ctagaaagta taggaacttc atcgataccg ggtagggggag gcgcttttcc caaggcagtc 3900

tggagcatgc gctttagcag ccccgctggg cacttggcgc tacacaagtg gcctctggcc 3960

tcgcacacat tccacatccc ccggtaggcg ccaaccggct ccgttctttg gtggcccctt 4020

cgcgccacct tctactcctc ccctagtcag gaagttcccc cccgccccgc agctcgcgtc 4080

gtgcaggacg tgacaaatgg aagtagcacg tctcactagt ctcgtgcaga tggacagcac 4140

cgctgagcaa tggaagcggg taggcctttg gggcagcggc caatagcagc tttgctcctt 4200

cgctttctgg gctcagaggc tgggaagggg tgggtccggg ggcgggctca ggggcgggct 4260

caggggcggg gcgggcgccc gaaggtcctc cggaggcccg gcattctgca cgcttcaaaa 4320

gcgcacgtct gccgcgctgt tctcctcttc ctcatctccg ggcctttcga cctgcagccc 4380

aagctagctt accatgaccg agtacaagcc cacggtgcgc ctcgccaccc gcgacgacgt 4440

ccccagggcc gtacgcaccc tcgccgccgc gttcgccgac taccccgcca cgcgccacac 4500

cgtcgatccg gaccgccaca tcgagcgggt caccgagctg caagaactct tcctcacgcg 4560

cgtcgggctc gacatcggca aggtgtgggt cgcggacgac ggcgccgcgg tggcggtctg 4620

gaccacgccg gagagcgtcg aagcgggggc ggtgttcgcc gagatcggcc cgcgcatggc 4680

cgagttgagc ggttcccggc tggccgcgca gcaacagatg gaaggcctcc tggcgccgca 4740

ccggcccaag gagcccgcgt ggttcctggc caccgtcggc gtctcgcccg accaccaggg 4800

caagggtctg ggcagcgccg tcgtgctccc cggagtggag gcggccgagc gcgccggggt 4860

gcccgccttc ctggagacct ccgcgccccg caacctcccc ttctacgagc ggctcggctt 4920

caccgtcacc gccgacgtcg aggtgcccga aggaccgcgc acctggtgca tgacccgcaa 4980

gcccggtgcc tgaggtacct ctcatgctgg agttcttcgc ccaccccaac ttgtttattg 5040

cagcttataa tggttacaaa taaagcaata gcatcacaaa tttcacaaat aaagcatttt 5100

tttcactgca ttctagttgt ggtttgtcca aactcatcaa tgtatcttat catcgatgaa 5160

gttcctattc tctagaaagt ataggaactt ctaacctccc gggtgacaga taacttcgta 5220

taatgtatgc tatacgaagt tatgtcgacg cggcgcgccg aattataata ctaacattac 5280

tgaagaaaat gcccaaaaga tggtaagttc ttgaggctac ccagggggtt attgattgct 5340

tcttaaagat cagaattact gcctataaaa ctggataagg aaatcataga gatctctcaa 5400

gtgtgaggat gagtgactgc ctctgtagct ctgatcctag tctcccagat ggctaaattc 5460

aattgacctt agagttcatc tggaaaattg ttatgaatga attatttgcc cagattccaa 5520

agatgagtga aaatgtttaa taaagttgcc atcactattc tcattatatt tggtatgtaa 5580

agcattcatg gaaatgttct aagtcgttat tgagccaata attttcttta gcttataatg 5640

ccaacaggtc tatccgagaa ctacaaatga catattaact gaaaaatgca actggggttt 5700

actgaaggca gcagcttagt aattaaggta accatggctt aggtgaaact ggacctggga 5760

attccttctt tcattgacac agagctctga ggaatttcca aaggtcacag aagaaaagct 5820

ataattaaac tagtcccaaa aaatctcagc ctactctggg aaagcagcat attttgtttg 5880

acaagtgcaa ggacttagaa cttttttttt tctcactgat cctgaagtgc cttttaagta 5940

tagttaagtg gtggaaaatt gagcaactat ttaagaaaag actctttttt ttcttcttcc 6000

agcaatgctt tccttcaaaa cggtagcttc aaaacttcct gtcttttaaa tgatcagggg 6060

gctgtgtgtt taaattattg ccattcatag aacagagtgg gtctgaggat gcctgtttcc 6120

tttgaaattc tatgccccct cccagttttc taaaatttaa gaaaccacag agactttgac 6180

aatgtagttg ccaaatgagt tgcttttaac tgctctaata gtttggtctt aagcttggcg 6240

taatcatggt catagctgtt tcctgtgtga aattgttatc cgctcacaat tccacacaac 6300

atacgagccg gaagcataaa gtgtaaagcc tggggtgcct aatgagtgag ctaactcaca 6360

ttaattgcgt tgcgctcact gcccgctttc cagtcgggaa acctgtcgtg ccagctgcat 6420

taatgaatcg gccaacgcgc ggggagaggc ggtttgcgta ttgggcgctc ttccgcttcc 6480

tcgctcactg actcgctgcg ctcggtcgtt cggctgcggc gagcggtatc agctcactca 6540

aaggcggtaa tacggttatc cacagaatca ggggataacg caggaaagaa catgtgagca 6600

aaaggccagc aaaaggccag gaaccgtaaa aaggccgcgt tgctggcgtt tttccatagg 6660

ctccgccccc ctgacgagca tcacaaaaat cgacgctcaa gtcagaggtg gcgaaacccg 6720

acaggactat aaagatacca ggcgtttccc cctggaagct ccctcgtgcg ctctcctgtt 6780

ccgaccctgc cgcttaccgg atacctgtcc gcctttctcc cttcgggaag cgtggcgctt 6840

tctcatagct cacgctgtag gtatctcagt tcggtgtagg tcgttcgctc caagctgggc 6900

tgtgtgcacg aaccccccgt tcagcccgac cgctgcgcct tatccggtaa ctatcgtctt 6960

gagtccaacc cggtaagaca cgacttatcg ccactggcag cagccactgg taacaggatt 7020

agcagagcga ggtatgtagg cggtgctaca gagttcttga agtggtggcc taactacggc 7080

tacactagaa gaacagtatt tggtatctgc gctctgctga agccagttac cttcggaaaa 7140

agagttggta gctcttgatc cggcaaacaa accaccgctg gtagcggtgg tttttttgtt 7200

tgcaagcagc agattacgcg cagaaaaaaa ggatctcaag aagatccttt gatcttttct 7260

acggggtctg acgctcagtg gaacgaaaac tcacgttaag ggattttggt catgagatta 7320

tcaaaaagga tcttcaccta gatcctttta aattaaaaat gaagttttaa atcaatctaa 7380

agtatatatg agtaaacttg gtctgacagt taccaatgct taatcagtga ggcacctatc 7440

tcagcgatct gtctatttcg ttcatccata gttgcctgac tccccgtcgt gtagataact 7500

acgatacggg agggcttacc atctggcccc agtgctgcaa tgataccgcg agacccacgc 7560

tcaccggctc cagatttatc agcaataaac cagccagccg gaagggccga gcgcagaagt 7620

ggtcctgcaa ctttatccgc ctccatccag tctattaatt gttgccggga agctagagta 7680

agtagttcgc cagttaatag tttgcgcaac gttgttgcca ttgctacagg catcgtggtg 7740

tcacgctcgt cgtttggtat ggcttcattc agctccggtt cccaacgatc aaggcgagtt 7800

acatgatccc ccatgttgtg caaaaaagcg gttagctcct tcggtcctcc gatcgttgtc 7860

agaagtaagt tggccgcagt gttatcactc atggttatgg cagcactgca taattctctt 7920

actgtcatgc catccgtaag atgcttttct gtgactggtg agtactcaac caagtcattc 7980

tgagaatagt gtatgcggcg accgagttgc tcttgcccgg cgtcaatacg ggataatacc 8040

gcgccacata gcagaacttt aaaagtgctc atcattggaa aacgttcttc ggggcgaaaa 8100

ctctcaagga tcttaccgct gttgagatcc agttcgatgt aacccactcg tgcacccaac 8160

tgatcttcag catcttttac tttcaccagc gtttctgggt gagcaaaaac aggaaggcaa 8220

aatgccgcaa aaaagggaat aagggcgaca cggaaatgtt gaatactcat actcttcctt 8280

tttcaatatt attgaagcat ttatcagggt tattgtctca tgagcggata catatttgaa 8340

tgtatttaga aaaataaaca aataggggtt ccgcgcacat ttccccgaaa agtgccacct 8400

gacgtctaag aaaccattat tatcatgaca ttaacctata aaaataggcg tatcacgagg 8460

ccctttcgtc 8470

<210> 28

<211> 19

<212> DNA

<213> Natural sequence

<220>

<223> Puro-F

<400> 28

aacctccccttctacgagc 19

<210> 29

<211> 24

<212> DNA

<213> Natural sequence

<220>

<223> 3arm-outR

<400> 29

tacagccagg atctggatgt cagc 24

<210> 30

<211> 5922

<212> DNA

<213> Artificial Sequence

<220>

<223> Genomic replacement sequence of Ace2 locus in mouse embryonic stem cells

<400> 30

ccctatggag tggagaagag tcttataatt ttttaaatgg gcagagaaat gaatttattt 60

ttaattttta gagacagggt ttctttgtat agctctagct gtctttgatt ggtagacaaa 120

gctgtcctca aactcagaga tcttccttcc tttgtctcct gagtgctggg attaaaggca 180

tggaccacca ctgccctgcc ccattctctc cattaatttt aagtgaatgc ttgcaaaagc 240

tcacttcttt ggtgaacagc ttcctttaca aataagtacc tttgccttcg tttttatagg 300

attcttaaaa agaaaaaaaa gattcagcca ggtggttgtg gtgcacacct ttaatcccag 360

cagtcaggag gcagaggaaa gcagatctct tgagtttgag gctagcctag tctacagagg 420

gagttccagg acagccaagg ctacagagag gaactgtcta aaaacaccaa gaaagagaga 480

aaggagagag ggagaggatg gatagctttat tgatagaatt gtcagaaaag gctataagtt 540

ccaatatgtg tcccatgatt tctaagtcta gccctttctg ttatagtaaa atcatagtac 600

accctcctcc tccagtgtat ctttaacagc ttttaaggaa catattaact aaatgtccag 660

gttttgattt ggccataaaa tgttagcaaa gctaaggttt tctaggatta atgaataaca 720

tgtctttatt tagtttactt aaaaaaatca ttctaaaata tctgtttaca tatctgtcct 780

ctccaggatt aacttcatat tggtccagca gcttgtttac tgttctcttc tgtttcttct 840

tctgcttttt ttttcttctc ttctcagtgc ccaacccaag ttcaaaggct gatgagagag 900

aaaaactcat gaagagattt tactctaggg aaagttgctc agtggatggg atcttggcgc 960

acggggaaag atgtcaagct cttcctggct ccttctcagc cttgttgctg taactgctgc 1020

tcagtccacc attgaggaac aggccaagac atttttggac aagtttaacc acgaagccga 1080

agacctgttc tatcaaagtt cacttgcttc ttggaattat aacaccaata ttactgaaga 1140

gaatgtccaa aacatgaata atgctgggga caaatggtct gcctttttaa aggaacagtc 1200

cacacttgcc caaatgtatc cactacaaga aattcagaat ctcacagtca agcttcagct 1260

gcaggctctt cagcaaaatg ggtcttcagt gctctcagaa gacaagagca aacggttgaa 1320

cacaattcta aatacaatga gcaccatcta cagtactgga aaagtttgta acccagataa 1380

tccacaagaa tgcttattac ttgaaccagg tttgaatgaa ataatggcaa acagtttaga 1440

ctacaatgag aggctctggg cttgggaaag ctggagatct gaggtcggca agcagctgag 1500

gccattat gaagagtatg tggtcttgaa aaatgagatg gcaagagcaa atcattatga 1560

ggactatggg gattattgga gaggagacta tgaagtaaat ggggtagatg gctatgacta 1620

cagccgcggc cagttgattg aagatgtgga acataccttt gaagagatta aaccattata 1680

tgaacatctt catgcctatg tgagggcaaa gttgatgaat gcctatcctt cctatatcag 1740

tccaattgga tgcctccctg ctcatttgct tggtgatatg tggggtagat tttggacaaa 1800

tctgtactct ttgacagttc cctttggaca gaaaccaaac atagatgtta ctgatgcaat 1860

ggtggaccag gcctggggatg cacagagaat attcaaggag gccgagaagt tctttgtatc 1920

tgttggtctt cctaatatga ctcaaggatt ctgggaaaat tccatgctaa cggacccagg 1980

aaatgttcag aaagcagtct gccatcccac agcttgggac ctggggaagg gcgacttcag 2040

gatccttatg tgcacaaagg tgacaatgga cgacttcctg acagctcatc atgagatggg 2100

gcatatccag tatgatatgg catatgctgc acaacctttt ctgctaagaa atggagctaa 2160

tgaaggattc catgaagctg ttggggaaat catgtcactt tctgcagcca cacctaagca 2220

tttaaaatcc attggtcttc tgtcacccga ttttcaagaa gacaatgaaa cagaaataaa 2280

cttcctgctc aaacaagcac tcacgattgt tgggactctg ccatttactt acatgttaga 2340

gaagtggagg tggatggtct ttaaagggga aattcccaaa gaccagtgga tgaaaaagtg 2400

gtgggagatg aagcgagaga tagttggggt ggtggaacct gtgccccatg atgaaacata 2460

ctgtgacccc gcatctctgt tccatgtttc taatgattac tcattcattc gatattacac 2520

aaggaccctt taccaattcc agtttcaaga agcactttgt caagcagcta aacatgaagg 2580

ccctctgcac aaatgtgaca tctcaaactc tacagaagct ggacagaaac tgttcaatat 2640

gctgaggctt ggaaaatcag aaccctggac cctagcattg gaaaatgttg taggagcaaa 2700

gaacatgaat gtaaggccac tgctcaacta ctttgagccc ttatttacct ggctgaaaga 2760

ccagaacaag aattcttttg tgggatggag taccgactgg agtccatatg cagaccaaag 2820

catcaaagtg aggataagcc taaaatcagc tcttggagat aaagcatatg aatggaacga 2880

caatgaaatg tacctgttcc gatcatctgt tgcatatgct atgaggcagt actttttaaa 2940

agtaaaaaat cagatgattc tttttgggga ggaggatgtg cgagtggcta atttgaaacc 3000

aagaatctcc tttaatttct ttgtcactgc acctaaaaat gtgtctgata tcattcctag 3060

aactgaagtt gaaaaggcca tcaggatgtc ccggagccgt atcaatgatg ctttccgtct 3120

gaatgacaac agcctagagt ttctggggat acagccaaca cttggacctc ctaaccagcc 3180

ccctgtttcc atatggctga ttgtttttgg agttgtgatg ggagtgatag tggttggcat 3240

tgtcatcctg atcttcactg ggatcagaga tcggaagaag aaaaataaag caagaagtgg 3300

agaaaatcct tatgcctcca tcgatattag caaaggagaa aataatccag gattccaaaa 3360

cactgatgat gttcagacct ccttttagaa cttgtttatt gcagcttata atggttacaa 3420

ataaagcaat agcatcacaa atttcacaaa taaagcattt ttttcactgc attctagttg 3480

tggtttgtcc aaactcatca atgtatctta acgcgtgcga agttcctatt ctctagaaag 3540

tataggaact tcatcgatac cgggtagggg aggcgctttt cccaaggcag tctggagcat 3600

gcgctttagc agccccgctg ggcacttggc gctacacaag tggcctctgg cctcgcacac 3660

attccacatc ccccggtagg cgccaaccgg ctccgttctt tggtggcccc ttcgcgccac 3720

cttctactcc tcccctagtc aggaagttcc cccccgcccc gcagctcgcg tcgtgcagga 3780

cgtgacaaat ggaagtagca cgtctcacta gtctcgtgca gatggacagc accgctgagc 3840

aatggaagcg ggtaggcctt tggggcagcg gccaatagca gctttgctcc ttcgctttct 3900

gggctcagag gctgggaagg ggtgggtccg ggggcgggct caggggcggg ctcaggggcg 3960

gggcgggcgc ccgaaggtcc tccggaggcc cggcattctg cacgcttcaa aagcgcacgt 4020

ctgccgcgct gttctcctct tcctcatctc cgggcctttc gacctgcagc ccaagctagc 4080

ttaccatgac cgagtacaag cccacggtgc gcctcgccac ccgcgacgac gtccccaggg 4140

ccgtacgcac cctcgccgcc gcgttcgccg actaccccgc cacgcgccac accgtcgatc 4200

cggaccgcca catcgagcgg gtcaccgagc tgcaagaact cttcctcacg cgcgtcgggc 4260

tcgacatcgg caaggtgtgg gtcgcggacg acggcgccgc ggtggcggtc tggaccacgc 4320

cggagagcgt cgaagcgggg gcggtgttcg ccgagatcgg cccgcgcatg gccgagttga 4380

gcggttcccg gctggccgcg cagcaacaga tggaaggcct cctggcgccg caccggccca 4440

aggagcccgc gtggttcctg gccaccgtcg gcgtctcgcc cgaccaccag ggcaagggtc 4500

tgggcagcgc cgtcgtgctc cccggagtgg aggcggccga gcgcgccggg gtgcccgcct 4560

tcctggagac ctccgcgccc cgcaacctcc ccttctacga gcggctcggc ttcaccgtca 4620

ccgccgacgt cgaggtgccc gaaggaccgc gcacctggtg catgacccgc aagcccggtg 4680

cctgaggtac ctctcatgct ggagttcttc gcccaccccca acttgtttat tgcagctttat 4740

aatggttaca aataaagcaa tagcatcaca aatttcacaa ataaagcatttttttcactg 4800

cattctagtt gtggtttgtc caaactcatc aatgtatctt atcatcgatg aagttcctat 4860

tctctagaaa gtataggaac ttctaacctc ccgggtgaca gataacttcg tataatgtat 4920

gctatacgaa gttatgtcga cgcggcgcgc cgaattataa tactaacatt actgaagaaa 4980

atgcccaaaa gatggtaagt tcttgaggct acccaggggg ttattgattg cttcttaaag 5040

atcagaatta ctgcctataa aactggataa ggaaatcata gagatctctc aagtgtgagg 5100

atgagtgact gcctctgtag ctctgatcct agtctcccag atggctaaat tcaattgacc 5160

ttagagttca tctggaaaat tgttatgaat gaattatttg cccagattcc aaagatgagt 5220

gaaaatgttt aataaagttg ccatcactat tctcattata tttggtatgt aaagcattca 5280

tggaaatgtt ctaagtcgtt attgagccaa taattttctt tagcttataa tgccaacagg 5340

tctatccgag aactacaaat gacatattaa ctgaaaaatg caactggggt ttactgaagg 5400

cagcagctta gtaattaagg taaccatggc ttaggtgaaa ctggacctgg gaattccttc 5460

tttcattgac acagagctct gaggaatttc caaaggtcac agaagaaaag ctataattaa 5520

actagtccca aaaaatctca gcctactctg ggaaagcagc atattttgtt tgacaagtgc 5580

aaggacttag aacttttttt tttctcactg atcctgaagt gccttttaag tatagttaag 5640

tggtggaaaa ttgagcaact atttaagaaa agactctttt ttttcttctt ccagcaatgc 5700

tttccttcaa aacggtagct tcaaaacttc ctgtctttta aatgatcagg gggctgtgtg 5760

tttaaattat tgccattcat agaacagagt gggtctgagg atgcctgttt cctttgaaat 5820

tctatgcccc ctcccagttt tctaaaattt aagaaaccac agagactttg acaatgtagt 5880

tgccaaatga gttgctttta actgctctaa tagtttggtc tt 5922

<210> 31

<211> 19

<212> DNA

<213> Natural sequence

<220>

<223> hACE2-F

<400> 31

tgatagtggt tggcattgt 19

<210> 32

<211> 4591

<212> DNA

<213> Artificial Sequence

<220>

<223> Genomic replacement sequence of the Ace2 locus in mouse embryonic stem cells after final deletion of PGK-puro

<400> 32

ccctatggag tggagaagag tcttataatt ttttaaatgg gcagagaaat gaatttattt 60

ttaattttta gagacagggt ttctttgtat agctctagct gtctttgatt ggtagacaaa 120

gctgtcctca aactcagaga tcttccttcc tttgtctcct gagtgctggg attaaaggca 180

tggaccacca ctgccctgcc ccattctctc cattaatttt aagtgaatgc ttgcaaaagc 240

tcacttcttt ggtgaacagc ttcctttaca aataagtacc tttgccttcg tttttatagg 300

attcttaaaa agaaaaaaaa gattcagcca ggtggttgtg gtgcacacct ttaatcccag 360

cagtcaggag gcagaggaaa gcagatctct tgagtttgag gctagcctag tctacagagg 420

gagttccagg acagccaagg ctacagagag gaactgtcta aaaacaccaa gaaagagaga 480

aaggagagag ggagaggatg gatagctttat tgatagaatt gtcagaaaag gctataagtt 540

ccaatatgtg tcccatgatt tctaagtcta gccctttctg ttatagtaaa atcatagtac 600

accctcctcc tccagtgtat ctttaacagc ttttaaggaa catattaact aaatgtccag 660

gttttgattt ggccataaaa tgttagcaaa gctaaggttt tctaggatta atgaataaca 720

tgtctttatt tagtttactt aaaaaaatca ttctaaaata tctgtttaca tatctgtcct 780

ctccaggatt aacttcatat tggtccagca gcttgtttac tgttctcttc tgtttcttct 840

tctgcttttt ttttcttctc ttctcagtgc ccaacccaag ttcaaaggct gatgagagag 900

aaaaactcat gaagagattt tactctaggg aaagttgctc agtggatggg atcttggcgc 960

acggggaaag atgtcaagct cttcctggct ccttctcagc cttgttgctg taactgctgc 1020

tcagtccacc attgaggaac aggccaagac atttttggac aagtttaacc acgaagccga 1080

agacctgttc tatcaaagtt cacttgcttc ttggaattat aacaccaata ttactgaaga 1140

gaatgtccaa aacatgaata atgctgggga caaatggtct gcctttttaa aggaacagtc 1200

cacacttgcc caaatgtatc cactacaaga aattcagaat ctcacagtca agcttcagct 1260

gcaggctctt cagcaaaatg ggtcttcagt gctctcagaa gacaagagca aacggttgaa 1320

cacaattcta aatacaatga gcaccatcta cagtactgga aaagtttgta acccagataa 1380

tccacaagaa tgcttattac ttgaaccagg tttgaatgaa ataatggcaa acagtttaga 1440

ctacaatgag aggctctggg cttgggaaag ctggagatct gaggtcggca agcagctgag 1500

gccattat gaagagtatg tggtcttgaa aaatgagatg gcaagagcaa atcattatga 1560

ggactatggg gattattgga gaggagacta tgaagtaaat ggggtagatg gctatgacta 1620

cagccgcggc cagttgattg aagatgtgga acataccttt gaagagatta aaccattata 1680

tgaacatctt catgcctatg tgagggcaaa gttgatgaat gcctatcctt cctatatcag 1740

tccaattgga tgcctccctg ctcatttgct tggtgatatg tggggtagat tttggacaaa 1800

tctgtactct ttgacagttc cctttggaca gaaaccaaac atagatgtta ctgatgcaat 1860

ggtggaccag gcctggggatg cacagagaat attcaaggag gccgagaagt tctttgtatc 1920

tgttggtctt cctaatatga ctcaaggatt ctgggaaaat tccatgctaa cggacccagg 1980

aaatgttcag aaagcagtct gccatcccac agcttgggac ctggggaagg gcgacttcag 2040

gatccttatg tgcacaaagg tgacaatgga cgacttcctg acagctcatc atgagatggg 2100

gcatatccag tatgatatgg catatgctgc acaacctttt ctgctaagaa atggagctaa 2160

tgaaggattc catgaagctg ttggggaaat catgtcactt tctgcagcca cacctaagca 2220

tttaaaatcc attggtcttc tgtcacccga ttttcaagaa gacaatgaaa cagaaataaa 2280

cttcctgctc aaacaagcac tcacgattgt tgggactctg ccatttactt acatgttaga 2340

gaagtggagg tggatggtct ttaaagggga aattcccaaa gaccagtgga tgaaaaagtg 2400

gtgggagatg aagcgagaga tagttggggt ggtggaacct gtgccccatg atgaaacata 2460

ctgtgacccc gcatctctgt tccatgtttc taatgattac tcattcattc gatattacac 2520

aaggaccctt taccaattcc agtttcaaga agcactttgt caagcagcta aacatgaagg 2580

ccctctgcac aaatgtgaca tctcaaactc tacagaagct ggacagaaac tgttcaatat 2640

gctgaggctt ggaaaatcag aaccctggac cctagcattg gaaaatgttg taggagcaaa 2700

gaacatgaat gtaaggccac tgctcaacta ctttgagccc ttatttacct ggctgaaaga 2760

ccagaacaag aattcttttg tgggatggag taccgactgg agtccatatg cagaccaaag 2820

catcaaagtg aggataagcc taaaatcagc tcttggagat aaagcatatg aatggaacga 2880

caatgaaatg tacctgttcc gatcatctgt tgcatatgct atgaggcagt actttttaaa 2940

agtaaaaaat cagatgattc tttttgggga ggaggatgtg cgagtggcta atttgaaacc 3000

aagaatctcc tttaatttct ttgtcactgc acctaaaaat gtgtctgata tcattcctag 3060

aactgaagtt gaaaaggcca tcaggatgtc ccggagccgt atcaatgatg ctttccgtct 3120

gaatgacaac agcctagagt ttctggggat acagccaaca cttggacctc ctaaccagcc 3180

ccctgtttcc atatggctga ttgtttttgg agttgtgatg ggagtgatag tggttggcat 3240

tgtcatcctg atcttcactg ggatcagaga tcggaagaag aaaaataaag caagaagtgg 3300

agaaaatcct tatgcctcca tcgatattag caaaggagaa aataatccag gattccaaaa 3360

cactgatgat gttcagacct ccttttagaa cttgtttatt gcagcttata atggttacaa 3420

ataaagcaat agcatcacaa atttcacaaa taaagcattt ttttcactgc attctagttg 3480

tggtttgtcc aaactcatca atgtatctta acgcgtgcga agttcctatt ctctagaaag 3540

tataggaact tctaacctcc cgggtgacag ataacttcgt ataatgtatg ctatacgaag 3600

ttatgtcgac gcggcgcgcc gaattataat actaacatta ctgaagaaaa tgcccaaaag 3660

atggtaagtt cttgaggcta cccagggggt tattgattgc ttcttaaaga tcagaattac 3720

tgcctataaa actggataag gaaatcatag agatctctca agtgtgagga tgagtgactg 3780

cctctgtagc tctgatccta gtctcccaga tggctaaatt caattgacct tagagttcat 3840

ctggaaaatt gttatgaatg aattatttgc ccagattcca aagatgagtg aaaatgttta 3900

ataaagttgc catcactatt ctcattatat ttggtatgta aagcattcat ggaaatgttc 3960

taagtcgtta ttgagccaat aattttcttt agcttataat gccaacaggt ctatccgaga 4020

actacaaatg acatattaac tgaaaaatgc aactggggtt tactgaaggc agcagcttag 4080

taattaaggt aaccatggct taggtgaaac tggacctggg aattccttct ttcattgaca 4140

cagagctctg aggaatttcc aaaggtcaca gaagaaaagc tataattaaa ctagtcccaa 4200

aaaatctcag cctactctgg gaaagcagca tattttgttt gacaagtgca aggacttaga 4260

actttttttt ttctcactga tcctgaagtg ccttttaagt atagttaagt ggtggaaaat 4320

tgagcaacta tttaagaaaa gactcttttt tttcttcttc cagcaatgct ttccttcaaa 4380

acggtagctt caaaacttcc tgtcttttaa atgatcaggg ggctgtgtgt ttaaattatt 4440

gccattcata gaacagagtg ggtctgagga tgcctgtttc ctttgaaatt ctatgccccc 4500

tcccagtttt ctaaaattta agaaaccaca gagactttga caatgtagtt gccaaatgag 4560

ttgcttttaa ctgctctaat agtttggtct t 4591

<210> 33

<211> 18

<212> DNA

<213> Artificial Sequence

<220>

<223> hACE2-qF

<400> 33

ggtcttcagt gctctcag 18

<210> 34

<211> 21

<212> DNA

<213> Artificial Sequence

<220>

<223> hACE2-qR

<400> 34

gcattcttgt ggattatctg g 21

<210> 35

<211> 22

<212> DNA

<213> Artificial Sequence

<220>

<223> Forward primer

<400> 35

ggggaacttc tcctgctaga at 22

<210> 36

<211> 22

<212> DNA

<213> Artificial Sequence

<220>

<223> Reverse primer

<400> 36

cagacatttt gctctcaagc tg 22

<210> 37

<211> 20

<212> DNA

<213> Artificial Sequence

<220>

<223> TaqMan Probes

<400> 37

ttgctgctgc ttgacagatt 20

Claims (32)

1. The sgRNA is characterized in that the sequence of the sgRNA is shown as SEQ ID NO. 1 or SEQ ID NO. 2.

2. The sgRNA of claim 1, wherein the sequence of the primers upstream and downstream of the synthesis of the sgRNA of SEQ ID NO. 2 is shown as SEQ ID NO. 4 and SEQ ID NO. 5, respectively.

3. The sgRNA of claim 1, wherein the sequences of the primers upstream and downstream of the synthesis of the sgRNA of SEQ ID No. 1 are shown in SEQ ID No. 6 and SEQ ID No. 7, respectively.

4. The sgRNA of claim 1, wherein the sgRNA-targeted gene is an animal ACE2 gene for site-directed cleavage of the ACE2 gene.

5. The sgRNA of claim 1, wherein the sgRNA is used to construct a humanized animal model.

6. The sgRNA of claim 1, wherein the target point of the sgRNA is located on exon 1 of the ACE2 gene of the animal.

7. The sgRNA of claim 6, wherein the target is within 140bp of the 5' utr of the ACE2 gene of the animal.

8. The sgRNA of any one of claims 4 to 7, wherein the animal is a mammal.

9. The sgRNA of claim 8, wherein the mammal is a rodent.

10. The sgRNA of claim 9, wherein the rodent is a mouse.

11. A carrier assembly, the carrier assembly comprising: (1) A vector comprising the sgRNA of any one of claims 1-10; (2) A targeting vector comprising a 5 'homology arm, a human ACE2 gene fragment, an SV40 polyA sequence, and a 3' homology arm; the targeting vector targets an animal ACE2 gene, the animal ACE2 gene comprising a target corresponding to the sgRNA of any one of claims 1 to 10.

12. The vector combination of claim 11, wherein the 5' homology arm is a 5' homology arm homologous to a 5' target sequence at a genomic locus of interest.

13. The vector combination of claim 12, wherein the targeting vector is used to initiate expression of a human gene of interest using an animal gene promoter after insertion of the CDS sequence of the human gene into the promoter and 5' utr region sequences of the animal gene.

14. The vector combination of claim 12, wherein the 3' homology arm is a 3' homology arm that is homologous to a 3' target sequence at a genomic locus of interest.

15. The vector combination of claim 14, wherein the targeting vector further comprises the screening marker PGK-Puro.

16. The carrier combination of claim 11, wherein the animal is a mammal.

17. The vector combination of claim 16, wherein the mammal is a rodent.

18. The vector combination of claim 13, wherein the animal is a mouse.

19. A DNA molecule encoding the sgRNA of any one of claims 1-10.

20. A cell comprising the sgRNA of any one of claims 1-10 or the targeting vector of any one of claims 11-18 or the DNA molecule of claim 19, said cell being incapable of developing into an animal subject, said cell excluding germ cells.

21. Use of the sgRNA of any one of claims 1 to 10 for the preparation of a genetically humanized cell line or a genetically humanized animal model, said animal being a mouse.

22. The use of claim 21, wherein the gene is ACE2.

23. A method for constructing a humanized animal cell line, wherein the sgRNA of any one of claims 1 to 10 is used in the method, the method comprising the steps of: (1) Constructing a targeting vector according to any one of the claims 11-18; (2) Introducing the constructed targeting vector and the vector with the sgRNA of any one of claims 1 to 10 attached thereto into embryonic stem cells of animal origin; (3) Culturing the embryonic stem cells in the step (2) into clones to obtain the embryonic stem cells; the animals were mice.

24. The method of claim 23, comprising introducing a human gene of interest into the animal cell such that the gene of interest expresses the CDS of the full length human gene of interest in situ within the animal cell.

25. The method of claim 24, wherein the gene of interest is ACE2.

26. The method of claim 23, wherein the method uses gene editing techniques for the construction of the humanized animal cell model.

27. The method of claim 26, wherein the gene editing technique comprises an embryonic stem cell-based DNA homologous recombination technique, a CRISPR/Cas9 technique.

28. The ACE2 gene humanized animal cell line produced by the method of any one of claims 23-27, which is incapable of developing into an animal subject, said cells not comprising germ cells.

29. A method of constructing a genetically humanized animal model comprising injecting the animal cell of claim 28 into an animal.

30. The method of claim 29, comprising forming the animal cells into an animal subject by tetraploid compensation or blastocyst injection.

31. A tissue, body fluid, cell or a fragment thereof or an extract thereof of a humanized mouse, or a tissue, body fluid, cell or a fragment thereof or an extract thereof of a humanized offspring of a humanized mouse, wherein the humanized mouse is constructed using the method of any one of claims 29-30, wherein the cell or tissue is incapable of developing into an animal subject, and wherein the cell does not comprise germ cells.

32. Use of a humanized animal model or a progeny thereof derived from the construction method of any one of claims 29-30 for the manufacture of human antibodies, or as a model system for pharmacological, immunological, microbiological and medical research, or for the production of animal experimental disease models for etiology research and/or for the development of new diagnostic and/or therapeutic strategies, or for screening, validating, evaluating or studying ACE2 gene function, ACE2 antibodies, drugs against ACE2 targets, pharmacodynamic research.

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