Additionally, consistent with the previous reports of ER stress in the SOD1 mouse models of ALS [46,47], the phosphorylation of PERK, but not that of GCN2, was increased in the spinal cord tissues from symptomatic mutant SOD1 mice (S6B Fig), suggesting that both PERK and MARK2 could contribute to the phosphorylation of eIF2α in these mice. Here, SOD1 is linked to amyotrophic lateral sclerosis.