Third, in ALS patient-specific induced-pluripotent stem cells, including ALS patient-derived VCP(R155C and R191Q), SOD1(A4V), and FUS(R521G) mutations, increased intron retention is a dominant feature during early neural differentiation22,23, which is in contrast to the most frequent exon skipping type detected in our study. Here, FUS is linked to amyotrophic lateral sclerosis.