C9 and amyotrophic lateral sclerosis: Although Swartz and colleagues reported lower levels of C9orf72 variants in iPSC skeletal muscles compared to iPSC-derived MNs and an absence of TDP-43 mislocalization or ubiquitin/p62-positive inclusions [91], another study showed that C9-ALS myocytes from iPSCs of C9orf72 ALS patients had increased expression and aggregation of TDP-43 [92], necessitating the need for more studies to investigate contribution of C9orf72 transcripts to skeletal muscle pathology.