ATXN2 and amyotrophic lateral sclerosis: When the number of expansions is between 27 and 34 repeats, this represents a major risk factor for the onset of ALS and is a cause of the production of abnormal protein ataxin-2; in fact, at the molecular level, poliQ expansion in ataxin-2 increases the interaction with TDP-43 and promotes the sequestration of TDP-43 to form irreversible cytoplasmic inclusions (SGs) with various RBPs (RNA-binding proteins) such as FUS, TDP-43, ataxin-2, and TAF15.