PTPN11 and myeloproliferative disorder: Further experimental evidence comes from another murine study reporting that a mutated form of protein tyrosine phosphatase SHP2 (encoded by PTPN11), a positive regulator of the RAS signalling pathway, in MSCs and osteoprogenitors, drives the development and progression of myeloproliferative neoplasms (MPN) through severe detrimental effects particularly on HSCs.