TP53 and neoplasm: None of the mice implanted with control p53−/− aNSCs transfected with Cas9 alone, or with Cas9 and gRNA pairs designed to induce the Fgfr3-Tacc3, Sec61g-Egfr, or Gga2-Prkcb rearrangements developed tumours during the observation period (Supplementary Table 1).