• Journal of Genetic Medicine
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• v.14 no.2
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• pp.71-74
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• 2017

Mutations in the DNA methyltransferase 1 gene (DNMT1) were reported to cause two phenotypes: OMIM 604121 and OMIM 614116. The first phenotype includes autosomal dominant cerebellar ataxia, deafness, and narcolepsy, which were reported to be caused by mutations in exon 21. The second phenotype includes hereditary sensory and autonomic neuropathy type 1E, which was suggested to be caused by mutations in exon 20 and 21. In this article, we report a novel heterozygous missense variant c.898A>C, p.(Lys300Gln) in exon 12 of DNMT1 in a young woman who presented with pure cerebellar ataxia. This report indicates that a mutation in exon 12 may lead to pure cerebellar ataxia. Another possibility is that the patient is currently in an early stage of the disease, and as the disease progresses, she will have more manifestations. To confirm or exclude this possibility, a subsequent follow-up study reporting the disease progression in this patient may be needed. Further reports of cases with the same mutation are needed to confirm the phenotype of this mutation.

• Annals of Clinical Neurophysiology
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• v.3 no.2
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• pp.151-155
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• 2001

SCA 1 is an autosomal dominant disorder. The phenotypic manifestations of SCA 1 are not specific, and thus, the diagnosis of SCA 1 rests on molecular genetic testing. The number of CAG repeats ranges from 6-44 in normal alleles and from 39-81 repeats in disease-causing alleles(chromosomal locus 6p22-23). The main clinical features of SCA 1 are ataxia, dysarthria, ophthalmoparesis, extrapyramidal signs without retinal degeneration. A 24-year-old woman with suspected family history presented with progressive cerebellar ataxia, dysarthria, ptosis, titubation and general weakness. Brain MRI revealed a moderate cerebellar atrophy. A genomic polymerase chain reaction(PCR) analysis showed 66 repeats at the SCA 1 locus.

• Journal of Genetic Medicine
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• v.4 no.1
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• pp.22-37
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• 2007

The autosomal dominant spinocerebellar ataxias (SCAs) are a group of neurodegenerative diseases, clinically and genetically heterogeneous, characterized by degeneration of spinocerebellar pathways with variable involvement of other neural systems. At present, 27 distinct genetic forms of SCAs are known: SCA1-8, SCA10-21, SCA23, SCA25-28, DRPLA (dentatorubral-pallidoluysian atrophy), and 16q-liked ADCA (autosomal dominant cerebellar ataxia). Epidemiological data about the prevalence of SCAs are restricted to a few studies of isolated geographical regions, and most do not reflect the real occurrence of the disease. In general a prevalence of about 0.3-2 cases per 100,000 people is assumed. As SCA are highly heterogeneous, the prevalence of specific subtypes varies between different ethnic and continental populations. Most recent data suggest that SCA3 is the commonest subtype worldwide; SCA1, SCA2, SCA6, SCA7, and SCA8 have a prevalence of over 2%, and the remaining SCAs are thought to be rare (prevalence <1%). In this review, we highlight and discuss the SCA7. The hallmark of SCA7 is the association of hereditary ataxia and visual loss caused by pigmentary macular degeneration. Visual failure is progressive, bilateral and symmetrical, and leads irreversibly to blindness. This association represents a distinct disease entity classified as autosomal dominant cerebellar ataxia (ADCA) type II by Harding. The disease affectsprimarily the cerebellum and the retina by the moderate to severe neuronal loss and gliosis, but also many other central nervous system structures as the disease progresses. SCA7 is caused by expansion of an unstable trinucleotide CAG repeat in the ATXN7 gene encoding a polyglutamine (polyQ) tract in the corresponding protein, ataxin-7. Normal ATXN7 alleles contain 4-35 CAG repeats, whereas pathological alleles contain from 36->450 CAG repeats. Immunoblott analysis demonstrated that ataxin-7 is widely expressed but that expression levels vary among tissues. Instability of expanded repeats is more pronounced in SCA7 than in other SCA subtypes and can cause substantial lowering of age at onset in successive generations termed ‘anticipation’ so that children may become diseased even before their parents develop symptoms. The strong anticipation in SCA7 and the rarity of contractions should have led to its extinction within a few generations. There is no specific drug therapy for this neurodegenerative disorder. Currently, therapy remains purely symptomatic. Cellular models and SCA7 transgenic mice have been generated which constitute valuable resources for studying the disease mechanism. Understanding the pathogenetic mechanisms of neurodegeneration in SCAs should lead to the identification of potential therapeutic targets and ultimately facilitate drug discovery. Here we summarize the clinical, pathological, and genetic aspects of SCA7, and review the current understanding of the pathogenesis of this disorder. Further, we also review the potential therapeutic strategies that are currently being explored in polyglutamine diseases.

• Journal of Yeungnam Medical Science
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• v.23 no.1
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• pp.118-123
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• 2006

Dentatorubropallidoluysian atrophy (DRPLA) is a rare neurodegenerative disorder usually inherited in an autosomal dominant pattern. DRPLA has been shown to be associated with expansion of an unstable cytosine-adenine-guanine (CAG) trinucleotide repeat in a gene on chromosome 12p. We evaluated a family with DRPLA that affected three members; A 35-year-old female presented with seven year history of gait ataxia, dysarthria and mild cognitive impairment. The MRI of the brain revealed diffuse cerebellar atrophy with an incidental lipoma in the midbrain. Her 30-year-old brother presented with progressive cerebellar ataxia that developed at the age of 20. Her grandmother and mother were reported to have developed ataxia during the late period of their life, and died at the age of 60 and 55, respectively. The demonstration of an expanded CAG repeat in the gene for DRPLA was used to confirm the diagnosis.

• Journal of Genetic Medicine
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• v.17 no.2
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• pp.92-96
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• 2020

Hypotonia, Ataxia, and Delayed Development Syndrome (HADDS) is an autosomal-dominant, extremely rare neurodevelopmental disorder caused by the heterozygous EBF3 gene mutation. EBF3 is located on chromosome 10q26.3 and acts as a transcription factor that regulates neurogenesis and differentiation. This syndrome is characterized by dysmorphism, cerebellar hypoplasia, urogenital anomaly, hypotonia, ataxia, intellectual deficit, and speech delay. The current report describes a 3-year-old Korean male carrying a de novo EBF3 mutation, c.589A>G (p.Asn197Asp), which was identified by whole exome sequencing. He manifested facial dysmorphism, hypotonia, strabismus, vermis hypoplasia, and urogenital anomalies, including vesicoureteral reflux, cryptorchidism, and areflexic bladder. This is the first report of a case of HADDS cause by an EBF3 mutation in the Korean population.

• Journal of the Korean Child Neurology Society
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• v.25 no.3
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• pp.200-203
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• 2017

Spinocerebellar ataxias (SCAs) are autosomal dominant neurodegenerative disorders which disrupt the afferent and efferent pathways of the cerebellum that cause cerebellar ataxia. Spectrin beta non-erythrocytic 2 (SPTBN2) gene encodes the ${\beta}-III$ spectrin protein with high expression in Purkinje cells that is involved in excitatory glutamate signaling through stabilization of the glutamate transporter, and its mutation is known to cause spinocerebellar ataxia type 5. Three years and 5 months old boy with delayed development showed leukodystrophy and cerebellar atrophy in brain magnetic resonance imaging (MRI). Diagnostic exome sequencing revealed that the patient has heterozygous mutation in SPTBN2 (p.Glu1251Gln) which is a causative genetic mutation for spinocerebellar ataxia type 5. With the patient's clinical findings, it seems reasonable to conclude that p.Glu1251Gln mutation of SPTBN2 gene caused spinocerebellar ataxia type 5 in this patient.