C9orf72 and amyotrophic lateral sclerosis: On the other hand, haploinsufficiency of C9orf72, a protein closely related with ALS and FTD, causes a ≈50% degradation of the translocase TIMMDC1, and a ≈30% blockage of complex I assembly, as measured by two-dimensional BN/SDS–PAGE analysis (Wang et al., 2021a).