PPM1D exon 6 mutations in our t-AML/t-MDS cohort were all truncating mutations with no particular hotspot, consistent with the distribution of exon 6 mutations found in CH and solid tumors (Figure 2A) (Dudgeon et al., 2013, Genovese et al., 2014, Ruark et al., 2013, Tan et al., 2009). Here, PPM1D is linked to cyclic hematopoiesis.