tp53 R217H and R242H mutant zebrafish exhibit dysfunctional p53 hallmarks and recapitulate Li-Fraumeni syndrome phenotypes

Li-Fraumeni syndrome (LFS) is a hereditary cancer predisposition syndrome associated with a highly penetrant cancer spectrum characterized by germline TP53 mutations. We characterized the first LFS zebrafish hotspot mutants, tp53 R217H and R242H (human R248H and R273H), and found these mutants exhibit partial-to-no activation of p53 target genes, have defective cell-cycle checkpoints, and display partial-to-full resistance to apoptosis, although the R217H mutation has hypomorphic characteristics. Spontaneous tumor development histologically resembling human sarcomas was observed as early as 6 months. tp53 R242H mutants had a higher lifetime tumor incidence compared to tp53 null and R217H mutants, suggesting it is a more aggressive mutation. We observed mutation-specific tumor phenotypes across tp53 mutants with associated diverse transcriptomic and DNA methylome profiles in tp53 mutant larvae, impacting metabolism, cell signalling, and biomacromolecule synthesis and degradation. These tp53 zebrafish mutants demonstrate fidelity to their human counterparts and provide new insights into underlying tumorigenesis mechanisms and kinetics that suggest metabolic rewiring and cellular signalling changes occur prior to tumor initiation, which will guide targeted therapeutics for LFS.