C9 and amyotrophic lateral sclerosis: In the current study, patient-derived C9-ALS iPSCs were differentiated into myogenic progenitors and skeletal myocytes using a transgene-free approach (Hosoyama et al., 2014; Jiwlawat et al., 2017) and then analyzed for signs of C9ORF72-linked pathology, including haploinsufficiency, RNA foci and DPR proteins.