PPM1D and myelodysplastic syndrome: 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).