PTPN11 and juvenile myelomonocytic leukemia: Furthermore, activating mutation of the Ptpn11 gene in mouse BM MSCs has been shown to promote the development and progression of the MDS/MPN juvenile myelomonocytic leukemia (JMML) through excessive production of the CC chemokine CCL3, which recruits monocytes to the area where HSCs also reside and activates them [44].