P-3. Investigation of the spinocerebellar ataxia type 10 mutation in the Cypriot population

Spinocerebellar ataxia type 10 belongs to the group of neurodegenerative diseases known as autosomal dominant cerebellar ataxias. Genetic studies in patients with SCA so far revealed 12 genes responsible for ADSCA and 12 mapped loci without gene identification. SCA10 is characterized by progressive ataxia and seizures. The underlying mutation is a large expansion of an ATTCT repeat in intron 9 of the SCA10 gene. Our aim is to determine the relative frequency of SCA10 in Cyprus, which constitutes part of our wider effort to identify the genetic defects of the Cypriot SCA sporadic patients and families, which prove to be exceptional in comparison with other populations. We analyzed the ATTCT repeats in 53 SCA patients, previously excluded from other genes (FRDA, SCA1-3, SCA6-8, SCA12, SCA17 and DRPLA). We also determined the size of repeats in 58 normal controls from the Cypriot polulation. The repeat lengths were analyzed by polymerase chain reaction followed by fragment analysis. Southern blot analysis was performed for samples with one allele detected, in order to confirm homozygosity or presence of a SCA10 expansion. Normal control sample repeat lengths ranged from 11 to 20 with 81% heterozygosity and the 14 repeats allele is more frequent (37%) in the Cypriot population. In the patient group, repeats ranged from 11 to19 with 83% heterozygosity. The rest of them (17%) have been confirmed to be homozygous for the normal range allele. Therefore the SCA10 mutation does not exist in the Cypriot SCA population under study. In conclusion, our results agree with other studies demonstrating that SCA10 is rare in populations other than the Mexican.