PPM1D/WIP1 is a phosphatase that dephosphorylates and inactivates many DDR mediators, such as ATM, p53, CHK2 and H2AX, and truncating exon 6 mutations were previously reported in DIPG as mutually exclusive with TP53 mutations [36–38]. The gene discussed is PPM1D; the disease is diffuse intrinsic pontine glioma.