This conclusion is substantiated by a number of observations, namely, (a) ectopic expression of exogenous STAU1 caused apoptosis through the PERK–CHOP pathway, (b) STAU1 knockout or knockdown cells showed attenuated UPR and apoptosis in response to ER stressors, and (c) basal levels of UPR activation and apoptosis in cellular and mouse models of SCA2, TDP-43 ALS, and C9ORF72 FTD were markedly decreased by STAU1 knockdown. Here, ATXN2 is linked to amyotrophic lateral sclerosis.