C9ORF72 repeat expansion is not detected in sporadic ataxia patients in mainland China.

Expansion of a GGGGCC hexanucleotide repeat in the gene C9ORF72 is a common pathogenic mutation in families with autosomal dominant frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). In order to understand whether pathogenic GGGGCC expansions of C9ORF72 are associated with spinocerebellar ataxia (SCA) in mainland China, we performed an experiment to determine the prevalence of pathogenic hexanucleotide expansions of C9ORF72 in a large cohort of Chinese Han patients with SCA. 411 sporadic patients with SCA and 314 healthy controls were screened for pathogenic hexanucleotide expansions of C9ORF72 utilizing a repeat primed polymerase chain reaction assay. However, no pathological repeat expansion of C9ORF72 was detected in either patients or controls. We therefore conclude that an expansion in C9ORF72 may not play a significant role in SCA in our cohort. However, more studies are needed to draw conclusions for the general population.