C9orf72 repeat expansions impair protein trafficking from the cytoplasm to the nucleus, and reduce the proportion of nuclear TDP-43 in patient-derived MNs (Zhang K. et al., 2015), thereby mimicking the nuclear depletion of TDP-43 in ALS patients (Neumann et al., 2006). Here, TARDBP is linked to amyotrophic lateral sclerosis.