Genetic and clinical analysis of spinocerebellar ataxia type 8 repeat expansion in Yugoslavia

Spinocerebellar ataxia type 8 (SCA8) is a slowly progressive ataxia causally associated with untranslated CTG repeat expansion on chromosome 13q21. However, the role of the CTG repeat in SCA8 pathology is not yet well understood. Therefore, we studied the length of the SCA8 CTA/CTG expansions (combined repeats, CRs) in 115 patients with ataxia, 64 unrelated individuals with non-triplet neuromuscular diseases, 70 unrelated patients with schizophrenia, and 125 healthy controls. Only one patient with apparently sporadic ataxia was identified with an expansion of 100 CRs. He had inherited the expansion from his asymptomatic father (140 CRs) and transmitted the mutation to his son (92 CRs). Paternal transmission in this family produced contractions of 40 and 8 CRs, respectively. None of the subjects from other studied groups had an expansion at the SCA8 locus. In the control group the number of CRs at the SCA8 locus ranged from 14 to 34. Our findings support the notion that allelic variants of the expansion mutation at the SCA8 locus can predispose to ataxia.

The status of SCA1, MJD/SCA3, FRDA, DRPLA and MD triplet containing genes in patients with Huntington disease and healthy controls

A number of human hereditary neuromuscular and neurodegenerative disorders are caused by the expansion of trinucleotide repeats within certain genes. Here we report the results of the analysis of five trinucleotide repeats containing genes (SCA1, MJD/SCA3, DRPLA, FRDA and MD) in HD patients and in a group of healthy controls. Allelic frequency distributions for SCA1 and FRDA genes were shifted toward larger alleles in the group of unrelated HD patients, compared to healthy controls. This linkage disequilibrium suggests a possible existence of a common mechanism of trinucleotide repeats expansion in these loci.