Global Gene Expression of hematopoietic stem cells expressing endogenous NrasG12D/G12D, NrasG12D/+, Nras+/+. Mus musculus

Oncogenic NRAS mutations are frequently identified in human myeloid leukemias. In mice, expression of endogenous oncogenic Nras (NrasG12D/+) in hematopoietic cells leads to expansion of myeloid progenitors, increased long-term reconstitution of bone marrow cells, and a chronic myeloproliferative neoplasm (MPN). However, acute expression of NrasG12D/+ in a pure C57BL/6 background does not induce hyperactivated GM-CSF signaling or increased proliferation in myeloid progenitors. It is thus unclear how NrasG12D/+ signaling promotes leukemogenesis. Here we show that hematopoietic stem cells (HSCs) expressing NrasG12D/+ serve as MPN initiating cells. They undergo moderate hyperproliferation with increased self-renewal. The aberrant NrasG12D/+ HSC function is associated with hyperactivation of ERK1/2 in HSCs. Conversely, downregulation of MEK/ERK by pharmacological and genetic approaches attenuates the cycling of NrasG12D/+ HSCs and prevents the expansion of NrasG12D/+ HSCs and myeloid progenitors. Our data delineate critical mechanisms of oncogenic Nras signaling in HSC function and leukemogenesis. Overall design: three NrasG12D/G12D HSCs samples, three NrasG12D/+ HSCs samples, two Nras+/+ HSCs control samples.