ATXN2 and frontotemporal dementia: ATXN2 belongs to a class of genes associated with microsatellite-expansion diseases, where an interrupted CAG repeat expansion has been associated with brain-related diseases including spinocerebellar ataxia type 2 (SCA2), frontotemporal lobar degeneration (FTLD), and amyotrophic lateral sclerosis (ALS)39,40.