The future of genetic diagnostics will see a move toward massively parallel next-generation seque... more The future of genetic diagnostics will see a move toward massively parallel next-generation sequencing of a patient's DNA. Amyotrophic lateral sclerosis (ALS) is one of the diseases that would benefit from this prospect. Exploring this idea, we designed a screening panel to sequence 25 ALS-linked genes and examined samples from 95 patients with both familial and sporadic ALS. Forty-three rare polymorphisms were detected in this cohort. A third of these have already been reported with respect to ALS, leaving 28 novel variants all open for further investigation. This study highlights the potential benefits of next-generation sequencing as a reliable, cost and time efficient, diagnostic, and research tool for ALS.
Mutations in the nuclear gene POLG (encoding the catalytic subunit of DNA polymerase gamma) are a... more Mutations in the nuclear gene POLG (encoding the catalytic subunit of DNA polymerase gamma) are an important cause of mitochondrial disease. The most common POLG mutation, A467T, appears to exhibit considerable phenotypic heterogeneity. The mechanism by which this single genetic defect results in such clinical diversity remains unclear. In this study we evaluate the clinical, neuropathological and mitochondrial genetic features of four unrelated patients with homozygous A467T mutations. One patient presented with the severe and lethal Alpers-Huttenlocher syndrome, which was confirmed on neuropathology, and was found to have a depletion of mitochondrial DNA (mtDNA). Of the remaining three patients, one presented with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), one with a phenotype in the Myoclonic Epilepsy, Myopathy and Sensory Ataxia (MEMSA) spectrum and one with Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoplegia (SANDO). All three had secondary accumulation of multiple mtDNA deletions. Complete sequence analysis of muscle mtDNA using the MitoChip resequencing chip in all four cases demonstrated significant variation in mtDNA, including a pathogenic MT-ND5 mutation in one patient. These data highlight the variable and overlapping clinical and neuropathological phenotypes and downstream molecular defects caused by the A467T mutation, which may result from factors such as the mtDNA genetic background, nuclear genetic modifiers and environmental stressors.
Journal of Neurology, Neurosurgery & Psychiatry, 2014
ABSTRACT Objectives Hemiplegic migraine (HM) is a rare form of migraine with aura with a prevalen... more ABSTRACT Objectives Hemiplegic migraine (HM) is a rare form of migraine with aura with a prevalence of 0.01–0.002%. Familial and sporadic forms are described and associated with ataxia and seizures. Causative genes include; CACNA1A, ATP1A2, SCNA1 for FHM types 1, 2 and 3 respectively. Recently PRRT2 mutations have been reported. However, significant numbers of patients remain genetically-undefined. The objectives are (i)Phenotype characterisation and (ii)Molecular investigations. Methods 50 probands were screened on a targeted gene panel designed for the Illumina TruSeq Custom Amplicon platform. Amplicons defined coding regions of known paroxysmal genes; CACNA1A, ATP1A2, SCN1A, KCNK18, KCNA1, ATP1A3, SLC2A1, SLC1A3, PRRT2, MR1, CACNB4. Variants were validated with Sanger sequencing. Results All patients reported classical symptoms; hemiplegic and/or hemisensory aura (100%), focal headache (100%), and complex aura (53%). Other features included epilepsy (13%), ataxia (10%), migraine with or without typical aura independent of HM (33%) and dyskinesia (2%). Variants were identified in: CACNA1A (12%), SCN1A (6%) and ATP1A2 (4%), PRRT2 (2%). Conclusions CACNA1A is a major disease gene but HM shows significant clinical and, genetic heterogeneity. The paroxysmal disorders gene panel will be an important diagnostic tool in investigating HM, related disorders and the role of ion channels. Whole-exome sequencing is underway for unresolved cases.
We report the clinical, biochemical, and molecular genetic findings in a family with an unusual m... more We report the clinical, biochemical, and molecular genetic findings in a family with an unusual mitochondrial disease phenotype harboring a novel mtDNA tRNA glutamic acid mutation at position 14709. The proband and his sister presented with congenital myopathy and mental retardation and subsequently developed cerebellar ataxia. Other family members had either adult-onset diabetes mellitus with muscle weakness or adult-onset diabetes
A family with maternally inherited myopathy and cardiomyopathy is described. Mitochondrial DNA an... more A family with maternally inherited myopathy and cardiomyopathy is described. Mitochondrial DNA analysis showed a heteroplasmic point mutation at position 3260 in the leucine transfer RNA gene, previously reported in a large Italian family with a similar phenotype. This observation confirms pathogenicity of this mutation and suggests phenotypic specificity.
A family exhibited maternal inheritance of a variable syndrome comprising ocular, neck and proxim... more A family exhibited maternal inheritance of a variable syndrome comprising ocular, neck and proximal upper limb weakness, psychiatric features, and sudden death. Of 15 definitely or probably affected individuals, 7 had died in early adult life, probably of respiratory failure. A novel point mutation of mitochondrial DNA, in a transfer RNA gene at position 3251, was detected in all living affected family members.
The future of genetic diagnostics will see a move toward massively parallel next-generation seque... more The future of genetic diagnostics will see a move toward massively parallel next-generation sequencing of a patient's DNA. Amyotrophic lateral sclerosis (ALS) is one of the diseases that would benefit from this prospect. Exploring this idea, we designed a screening panel to sequence 25 ALS-linked genes and examined samples from 95 patients with both familial and sporadic ALS. Forty-three rare polymorphisms were detected in this cohort. A third of these have already been reported with respect to ALS, leaving 28 novel variants all open for further investigation. This study highlights the potential benefits of next-generation sequencing as a reliable, cost and time efficient, diagnostic, and research tool for ALS.
Mutations in the nuclear gene POLG (encoding the catalytic subunit of DNA polymerase gamma) are a... more Mutations in the nuclear gene POLG (encoding the catalytic subunit of DNA polymerase gamma) are an important cause of mitochondrial disease. The most common POLG mutation, A467T, appears to exhibit considerable phenotypic heterogeneity. The mechanism by which this single genetic defect results in such clinical diversity remains unclear. In this study we evaluate the clinical, neuropathological and mitochondrial genetic features of four unrelated patients with homozygous A467T mutations. One patient presented with the severe and lethal Alpers-Huttenlocher syndrome, which was confirmed on neuropathology, and was found to have a depletion of mitochondrial DNA (mtDNA). Of the remaining three patients, one presented with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), one with a phenotype in the Myoclonic Epilepsy, Myopathy and Sensory Ataxia (MEMSA) spectrum and one with Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoplegia (SANDO). All three had secondary accumulation of multiple mtDNA deletions. Complete sequence analysis of muscle mtDNA using the MitoChip resequencing chip in all four cases demonstrated significant variation in mtDNA, including a pathogenic MT-ND5 mutation in one patient. These data highlight the variable and overlapping clinical and neuropathological phenotypes and downstream molecular defects caused by the A467T mutation, which may result from factors such as the mtDNA genetic background, nuclear genetic modifiers and environmental stressors.
Journal of Neurology, Neurosurgery & Psychiatry, 2014
ABSTRACT Objectives Hemiplegic migraine (HM) is a rare form of migraine with aura with a prevalen... more ABSTRACT Objectives Hemiplegic migraine (HM) is a rare form of migraine with aura with a prevalence of 0.01–0.002%. Familial and sporadic forms are described and associated with ataxia and seizures. Causative genes include; CACNA1A, ATP1A2, SCNA1 for FHM types 1, 2 and 3 respectively. Recently PRRT2 mutations have been reported. However, significant numbers of patients remain genetically-undefined. The objectives are (i)Phenotype characterisation and (ii)Molecular investigations. Methods 50 probands were screened on a targeted gene panel designed for the Illumina TruSeq Custom Amplicon platform. Amplicons defined coding regions of known paroxysmal genes; CACNA1A, ATP1A2, SCN1A, KCNK18, KCNA1, ATP1A3, SLC2A1, SLC1A3, PRRT2, MR1, CACNB4. Variants were validated with Sanger sequencing. Results All patients reported classical symptoms; hemiplegic and/or hemisensory aura (100%), focal headache (100%), and complex aura (53%). Other features included epilepsy (13%), ataxia (10%), migraine with or without typical aura independent of HM (33%) and dyskinesia (2%). Variants were identified in: CACNA1A (12%), SCN1A (6%) and ATP1A2 (4%), PRRT2 (2%). Conclusions CACNA1A is a major disease gene but HM shows significant clinical and, genetic heterogeneity. The paroxysmal disorders gene panel will be an important diagnostic tool in investigating HM, related disorders and the role of ion channels. Whole-exome sequencing is underway for unresolved cases.
We report the clinical, biochemical, and molecular genetic findings in a family with an unusual m... more We report the clinical, biochemical, and molecular genetic findings in a family with an unusual mitochondrial disease phenotype harboring a novel mtDNA tRNA glutamic acid mutation at position 14709. The proband and his sister presented with congenital myopathy and mental retardation and subsequently developed cerebellar ataxia. Other family members had either adult-onset diabetes mellitus with muscle weakness or adult-onset diabetes
A family with maternally inherited myopathy and cardiomyopathy is described. Mitochondrial DNA an... more A family with maternally inherited myopathy and cardiomyopathy is described. Mitochondrial DNA analysis showed a heteroplasmic point mutation at position 3260 in the leucine transfer RNA gene, previously reported in a large Italian family with a similar phenotype. This observation confirms pathogenicity of this mutation and suggests phenotypic specificity.
A family exhibited maternal inheritance of a variable syndrome comprising ocular, neck and proxim... more A family exhibited maternal inheritance of a variable syndrome comprising ocular, neck and proximal upper limb weakness, psychiatric features, and sudden death. Of 15 definitely or probably affected individuals, 7 had died in early adult life, probably of respiratory failure. A novel point mutation of mitochondrial DNA, in a transfer RNA gene at position 3251, was detected in all living affected family members.
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Papers by Mary Sweeney