ATF4 and amyotrophic lateral sclerosis: The activation of the PERK pathway (PERK and eIF2α phosphorylation; ATF4 and CHOP expression) was also observed in various ALS models, including mutant SOD1-expressing mice [245,246,254], ALS-related mutants (SOD1, FUS, TDP-43)-expressing cells [253,255,256], Drosophila model expressing TDP-43 aggregates [257], and patients’ spinal cord samples with sALS [247].