In addition, a recent study has revealed that calpain, a Ca2+‐dependent protease, cleaves TAR DNA binding protein 43 (TDP‐43), a protein abnormally accumulated in the lesion of sporadic ALS (Arai et al, 2006; Neumann et al, 2006), and induces the aggregation of TDP‐43 (Yamashita et al, 2012). Here, TARDBP is linked to amyotrophic lateral sclerosis.