Clinical characteristics and gene mutation analysis of hereditary spinocerebellar ataxia type 7: a study of 2 Chinese families

Objective To study the clinical characteristics and gene mutation of hereditary spinocerebellar ataxia type 7 (SCA7). Methods The regions of SCA 7 gene containing CAG repeat were amplified by means of PCR and agarose gelelectrophoresis (AGE) technique in 26 patients and 37 normal family members from 5 families with autosomal dominant SCA. The abnormal allele fragments were sequenced by DNA sequencing machine. The correlation between clinical manifestations and CAG repeat size in SCA 7 gene product was analyzed. Results The patients carried 44-50 repeated CAG in the SCA7 allele of 2 SCA 7 gene families with main clinical manifestations as ataxia, hypopsia and retinal pigmental degeneration. About 10-30 repeated CAGs in the SCA7 allele were seen in other healthy members. Conclusion Expanded triplet repeats in SCA 7 gene contributes to the pathologic phenotype,and molecular genetic analysis is effective in the diagnosis and differentiation of SCA 7 gene. Key words: Spinocerebellar ataxia;  Allele;  Trinucleotide repeat;  Retinal pigmental degeneration