RESUMO
Autosomal dominant cerebellar ataxias (ADCAs) comprise a group of genetically heterogeneous neurodegenerative disorders among which spinocerebellar ataxia type 3 (SCA3) represents the most common form of SCAs worldwide. The fragments of SCA3/MJD gene,which is the member of family GXPL1,were amplified by polymerase chain reaction (PCR). The PCR products of SCA3/MJD gene were detected with capillary electrophoresis (CE) and sequencing to evaluate the size of CAG repeats, feature in the transmission and the mutation in the family with SCA3 in Guangxi province. The results showed that the exon 10 of the SCA3/MJD gene contains 64-71 CAG repeats in all of the affected individuals and three asymptomatic carriers of the family. The number of the CAG repeats during transmission in the normal individuals carrying CGG allele remains consistent, suggesting that CGG allele could have no effect on intergenerational stability of CAG repeats in normal individuals. In addition, two novel point mutations were identified: IVS9-113 T > C in the intronic region and a missense mutation 220 G > A (Glu > Gly) in the encoding region. These two novel point mutations have not been reported and the effect of the mutations on the phenotype of SCA3 is not clear.