To investigate whether the molecular changes observed upon loss of FUS, TAF15 or both proteins were relevant to ALS pathogenesis, we obtained fibroblasts from two ALS patients with the causative R521G mutation in FUS. The fibroblasts were reprogrammed into iPSCs and subjected to cellular, molecular and genetic characterization to confirm that they are pluripotent (Supplementary Fig. 6b), exhibit a normal karyotype and harbour the presence or absence of the mutation at nucleotide position 1,561 (Supplementary Fig. 6c). Here, FUS is linked to amyotrophic lateral sclerosis.