We contributed to these earlier in vivo studies by showing that Xist deletion in hematopoietic stem cells (HSCs) leads to female-specific lethality due to a range of aggressive hematologic malignancies in the form of mixed myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) and chronic myelomonocytic leukemia (CMML)18. The gene discussed is XIST; the disease is chronic myelomonocytic leukemia.