ATXN2 and cerebellar ataxia: Spinocerebellar ataxia (SCA) type 2 and 3 are caused by cytosine–adenine–guanine (CAG)n repeat expansions in ATXN2 and ATXN3 genes (OMIM 601517, 607047), which are the most common types of SCAs in China (Wang et al., 2011).