Repeat-containing transcripts of the mutated C9orf72 gene can form RNA foci enriched with RNA-binding proteins in induced pluripotent stem cell (iPSC)-derived neurons from ALS and FTD patients, as well as in motor neurons of C9orf72-ALS patients [37,38,39,40]. The gene discussed is PTBP1; the disease is amyotrophic lateral sclerosis.