Frequency of SCA1, SCA2, SCA3/MJD, SCA6, SCA7, and DRPLA CAG Trinucleotide Repeat Expansion in Patients With Hereditary Spinocerebellar Ataxia From Chinese Kindreds

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Abstract
THE HEREDITARY spinocerebellar ataxias (SCAs) are a heterogeneous group of neurodegenerative disorders including Machado-Joseph disease (MJD) and a variety of other ataxia subtypes, which share progressive deterioration in balance and coordination. Most of the familial SCAs are inherited as autosomal dominant traits. Because dentatorubropallidoluysian atrophy (DRPLA) can be seen initially with an SCA phenotype, some authors also classify it into the SCAs. To date, at least 10 genetic loci have been mapped to different chromosomes by linkage analysis, which confirm that hereditary SCAs are genetically heterogeneous. The genes responsible for SCA1 (spinocerebellar ataxia type 1),1 SCA2,2-4 SCA3/MJD (spinocerebellar ataxia type 3/MJD),5 SCA6,6 SCA7,7 and DRPLA8,9 have been cloned. All are caused by CAG trinucleotide repeat expansion in open reading frames of corresponding gene, resulting in an expanded glutamine repeat. To assess the frequencies of different SCA genotypes among Chinese families, we have detected the SCA1, SCA2, SCA3/MJD, SCA6, SCA7, and DRPLA CAG trinucleotide repeat expansions in 167 patients with autosomal dominant SCA from 85 Chinese kindreds and 37 patients with sporadic SCA. To our knowledge, we provide the first documentation of SCA genotypes in Mainland China.