To assess the role of RRP7A in neurogenesis, we next used the CRISPR/Cas9 system to induce deletions in exon 2 of the Rrp7a gene in P19CL6 cells, a mouse teratocarcinoma stem cell line that differentiates into neurons upon retinoic acid (RA) stimulation26 (Supplementary Fig. 3a, b). The gene discussed is RRP7A; the disease is teratocarcinoma.