BCOR and myelodysplastic syndrome: Analysis of the clonal composition and mutation hierarchies using the PyClone algorithm18 revealed that TP53, DNMT3A, BCOR and STAG2 were mostly founder mutations in the corresponding MDS subgroup, and RUNX1 frequently occurred as a secondary hit in dominant clones driven by BCOR and STAG2 mutations (Extended Data Fig. 4a–c).