ATXN2 and amyotrophic lateral sclerosis: In the last years, the discovery of a hexanucleotide repeat expansion in chromosome 9 open reading frame 2 (C9orf72) as the main genetic cause of Amyotrophic Lateral Sclerosis (ALS) and the association between intermediate repeats in ataxin 2 (ATXN2) with this disorder have suggested that repetitive sequences in human genome play a major role in ALS pathophysiology36–38.