[Molecular genetic diagnosis and clinical analysis of spinocerebellar ataxia type 7].

Objective: To study the molecular genetic diagnosis and clinical characteristics of spinocerebellar ataxia type 7 (SCA7).

Methods: This study included 43 patients with autosomal dominant SCA from 36 families, 38 sporadic SCA patients, 60 healthy individuals from the SCA families and 44 normal controls without family SCA history. The SCA7 (CAG)n mutations were detected by PCR, denaturing polyacrylamide gel electrophoresis and silver staining technique. The abnormal allele fragments were sequenced by ABI373 DNA sequencing machine.

Results: Normal alleles of SCA7 were found to have 9 to 19 CAG repeats. Two familial SCA and one sporadic patients were identified by detecting the presence of abnormal CAG-repeat expansion in the SCA7 alleles, which was confirmed by DNA sequencing. The repeats of CAG were 65, 65, and 63 respectively.

Conclusions: Abnormal CAG expansion is the pathogenic cause of SCA7. Molecular genetic analysis is effective for the diagnosis of SCA, prediction of presymptomatic patients and genetic counseling.