C9orf72 and amyotrophic lateral sclerosis: Other examples are ATXN2, in which more than 34 repeats cause SCA2, while 29–33 are risk factor for ALS [32,33], and ATXN1, in which more than 38 repeat cause SCA1, while ≥33 are risk factor for ALS, mostly in C9orf72 expansion carriers [34].