MPL and myeloproliferative neoplasm: Thrombopoietin and its receptor MPL are primary regulators of megakaryocyte growth and differentiation.236–238 The pathogenetic mutation MPLW515L induces abnormal activation of JAK-STAT signaling and participates in MPN development.231,239 MPLW515L promotes hematopoietic cell proliferation and cellular responses to thrombopoietin.