Hemogenic mesoderm heterogeneity, regulation, and function

About This Grant

PROJECT SUMMARY / ABSTRACT The mammalian hematopoietic system develops in the early embryo through a series of spatio-temporally separated programs, each of which harbors different functional potential, culminating in the specification of the hematopoietic stem cell (HSC). The overall goal of our research is to understand the origins and development of each program in the embryonic hematopoietic system. Where does each developmental program originate from? How does it develop? Why is each different? And, is there clinical utility to embryonic cell types that are no longer found in adult donors? Dr. Sturgeon's prior work has focused on these questions, through the lens of human pluripotent stem cell (hPSC) directed differentiation, leading to the pivotal discovery of hematopoietic commitment occurring very early, within nacent mesoderm, referred to as hemogenic mesoderm (HM). The proposed research program builds upon Dr. Sturgeon's productive research track record to delineate the molecular and transcriptional mechanisms by which HM gives rise to the embryonic hematopoietic programs. Dr. Sturgeon has shown that HMs are found in multiple immunophenotypically distinct subsets, each of which are specified in ACTIVIN/NODAL- and/or WNT-dependent processes. Further, Dr. Sturgeon has found that each HM first gives rise to a hemogenic endothelial cell (HEC) population, in VEGF- and RA-dependent processes. HM express genes associated with early gastrulation, yet each HM is highly restricted, ultimately each giving rise to a specific hematopoietic program, such as yolk sac-like erythromyeloid progenitors (EMPs), or intra- embryonic-like definitive multipotent progenitors (MPPs). Finally, Dr. Sturgeon has found that hematopoietic lineages common across multiple HM populations harbor distinct functional properties from one another. Building off these groundbreaking findings, the research program is divided into 3 projects. The first project will delineate the signal, transcriptional, and epigenetic mechanisms underlying how each hematopoietic program is specified and functionally restricted. These studies will improve our ability to obtain progenitors from each program, including the HSC. The second project will define the mechanisms regulating how HECs give rise to different lineages. Finally, the third project will continue our studies on the translational potential of hematopoietic lineages from each developmental program. Collectively, these studies will provide us with a more comprehensive understanding of hematopoietic development. This is of fundamental importance to basic biology, and the insights generated from these studies will have clinical implications, such as the in vitro generation of HSCs or other embryonic hematopoietic lineages for a wide array of regenerative medicine applications.