A repeat-primed PCR assay for pentanucleotide repeat alleles in spinocerebellar ataxia type 37.

Spinocerebellar ataxia 37 (SCA37) is caused by an (ATTTC) insertion in a polymorphic ATTTT repeat in the non-coding region of DAB1. The non-pathogenic alleles have a configuration [(ATTTT)], whereas pathogenic alleles have a complex structure of [(ATTTT)(ATTTC)(ATTTT)]. Molecular diagnosis of SCA37 is laborious because about 7% of the pentanucleotide repeat alleles in DAB1 are larger than 30 units and, thus, fail to amplify with standard PCR conditions, resulting in apparently homoallelism or in complete lack of PCR amplification in several cases.