Curiously, polyQ tract expansion in human ataxin-2 is associated with two neurodegenerative diseases, amyotrophic lateral sclerosis 13 associated with the intermediate expansions of CAG repeat (between 24 and 35 repeats) [302] and spinocerebellar ataxia 2 (SCA2) [92,93,303]. The gene discussed is ATXN2; the disease is spinocerebellar ataxia type 2.