rearrangement calls were validated by targeted deep sequencing and PCR, respectively (Extended Data Figs 9, 10 and Methods). One plausible explanation for the lack of increased mutagenesis in Aldh2−/−Fancd2−/−Trp53−/− HSCs is the possibility that the very small number of HSCs in Aldh2−/−Fancd2−/− mice might have undergone more replicative cycles, thereby accruing a larger number of mutations. To address this, we quantified the frequency of ‘clock’ mutations (C to T at CpG sites), but this analysis showed no significant difference between Aldh2−/−Fancd2−/− and Aldh2−/−Fancd2−/−Trp53−/− HSCs (Fig. 6f). These results indicate that aldehyde-induced DNA damage induces p53 leading to HSC attrition, which is inconsistent with p53 being a negative regulator of Fanconi anaemia repair, as recently reported27. However, while Trp53 deletion completely rescues HSC depletion, this does not occur at the expense of genome stability in stem cells.
