Consistent with these findings, the hemizygous deletion of PERK in another familial ALS mouse model (SOD1 G85R) is detrimental, accelerating disease onset and shortening life-span, except in later disease, when it is protective (Wang et al., 2011)—possibly due to the greater influence of factors affecting ageing neurons later in disease, discussed above. This evidence concerns the gene EIF2AK3 and amyotrophic lateral sclerosis.