Overview of repeats
Expansions of pentanucleotide ATTCT repeats in an intron of the ATXN10 gene is responsible for the development of spinocerebellar ataxia type 10 (SCA10) as reported by Matsuura et al. (2000, 2006). They reported that the number of repeats in a healthy population was between 10 and 29, whereas pathological repeats in affected individuals were in the range of 800-4500 (Matsuura et al., 2000; Matsuura et al., 2006). Apart from that, there is also evidence of repeat lengths with reduced penetrance. For example, an affected individual was identified with a 400 repeat expansion, whereas her siblings with 360 repeats and the father with 370 repeats were unaffected (Alonso et al., 2006). Also, a patient with early-onset ataxia was described, having 280 ATTCT repeats, while her mother was unaffected with the same repeat length (Matsuura et al., 2006). Due to the huge variability, we have specified here an intermediate range between 30-799.