TP53 and neoplasm: While >50% of mice in which Trp53 was edited before Nf1 came down with tumors with 37% harboring macroscopic tumors, no tumor development was observed in mice in which Nf1 was edited before Trp53, and only one control mouse with an sgRNA targeting Nf1 presented one microscopic (Trp53 negative) tumor nodule (Fig. 5c).