The genetic inhibition of p110δ in vivo led to reduced splenomegaly, decreased phosphorylation of Akt and Erk, and decreased progenitor cell hypersensitivity to GM-CSF in a Shp2D61Y/+;Mx1cre+ mouse model of JMML. The gene discussed is CSF2; the disease is juvenile myelomonocytic leukemia.