RUNX1-mediated regulation of MEP fate specification

(PLEASE KEEP IN WORD, DO NOT PDF) Enter the text here that is the new abstract information for your application. This section must be no longer than 30 lines of text. Abstract Fate specification is a fundamental aspect of hematopoietic stem and progenitor cell biology. The proposed studies are focused on the still elusive molecular mechanisms that direct bipotent megakaryocyte-erythroid progenitors (MEP) towards downstream unipotent megakaryocytic progenitors (MkP) and erythroid progenitors (ErP), which are essential for platelet and red blood cell production. Building on our published studies and new preliminary data, we will test how the transcription factor RUNX1, one of the most commonly mutated genes in acute myeloid leukemia, regulates MEP fate. In collaboration with experts in proteomics, and transcriptional initiation we will use state-of-the-art approaches to test the hypothesis that phosphorylation of specific serines and threonines of RUNX1 by CDK9 and other kinases promotes the transcriptional elongation of genes that promote the megakaryocytic fate whereas inhibition of this phosphorylation promotes the erythroid fate. Sorted MEP, MkP and ErP populations provide a unique opportunity to study mechanisms of fate specification as they are extremely close to one another developmentally, yet have distinctly different differentiation potential. Using cell and molecular biology along with highly innovative proteomics approaches, we will 1) determine the differential levels of phospho-RUNX1 proteoforms in primary MEP, MkP, and ErP; 2) test the degree to which the upstream kinase CDK9 promotes RUNX1 Serine and Threonine phosphorylation; and 3) assess potential downstream mechanisms by which phosphorylated RUNX1 regulates MEP fate specification. This research holds significant promise for advancing our understanding of hematopoiesis and has implications for therapeutic interventions in Hematology and Transfusion Medicine as well as broad implications regarding fundamental mechanisms in fate specification.