Neuropathy of the HSPC niche is present and essential for disease development in experimental models of JAK2<sup>V617F+</sup> myeloproliferative neoplasms (MPN) and MLL-AF9<sup>+</sup> acute myeloid leukemia (AML), and it is present in the BM of human MPN and AML patients [3-6]. The gene discussed is MLLT3; the disease is acute myeloid leukemia.