The Role of Megakaryocytes in Myeloproliferative Neoplasms. (360G-Wellcome-107477_Z_15_Z)

In Primary Myelofibrosis (PMF), acquired genetic abnormalities affecting JAK- STAT signalling lead to haematopoietic stem/progenitor cell proliferation, mobilization, and bone marrow (BM) fibrosis. BM infiltration with pathological megakaryocytes (MKs) is ubiquitous, with many low-ploidy/immature MKs. PMF- derived MKs secrete supra-physiological levels of angiogenic/fibrogenic cytokines and proteases. However, the mechanisms underlying abnormal megakaryopoiesis and its contribution to pathological fibrosis are poorly understood. PROJECT AIMS: (1) Determine the functionally-significant abnormalities in PMF megakaryopoiesis; (2) Identify the molecular basis for MK-mediated fibrosis. To define the cellular hierarchy associated with early MK commitment of bipotential MK-erythroid progenitors (MEP), I have devised a 10-fluorochrome immunophenotyping panel that identifies 3 distinct MEP subpopulations with different MK potential that have not previously been described and appear to be MK-b iased in PMF. In this Fellowship I will perform transcriptome profiling by RNASeq of single cell and MEP/MKP subpopulations. Together these novel approaches will enable a reconstruction of the cellular hierarchies in normal and malignant megakaryopoiesis. PMF will be compared to healthy controls; patients with Immune Thrombocytopenia (increased non-clonal MKs), and transient myeloproliferative disorder (clonal megakaryopoiesis and fibrosis; collaboration with I.Roberts), and gene targeting will be employed to confirm the pathological significance of dysregulated pathways identified for MK-mediated fibrosis.