Also, mutations in the gene encoding the chaperone Ubiquilin 2 (UBQLN2) are associated with X-linked forms of ALS [18]; this age-related form of ALS shows dysfunctional mitophagy caused by altered function of the UBQLN2 protein, which interacts with Hsp70 [19]. Here, HSPA4 is linked to amyotrophic lateral sclerosis.