EIF2AK3 and amyotrophic lateral sclerosis: In our study, PERK protein level was upregulated 2.6-fold in WG muscle of ALS-Tg vs. WT mice at 70d (p = 0.01), 5.4-fold at 90d (p = 0.025) and 5.2-fold at 120–140d (p = 0.001; Figures 1A,C).