Defining Mechanisms of SAMD1 in Hematopoiesis

ABSTRACT Hematopoiesis produces ~300 billion blood cells daily. Hematopoietic stem and progenitor cells (HSPCs) give rise to lineage-committed progenitors (e.g., the megakaryocyte-erythrocyte progenitor (MEP)), which differentiate into mature cell types. Understanding mechanisms required for HSPC and MEP fate determination

has important implications for pathologies such as leukemia, chronic anemia, and myelodysplastic syndrome (MDS), as all can be caused by mutations and misregulation of HSPC and/or MEP activities. I identified that the sterile alpha motif protein-1 (SAMD1) protein is expressed highly in HSPCs and MEPs. My preliminary data

indicates that SAMD1 promotes Kit signaling, impairs erythropoiesis and HSPC activity, and modulates the expression of multiple genes required for hematopoiesis/erythropoiesis, including GATA2. In other contexts, SAMD1 acts as a transcriptional co-repressor with LSD1 to control transcription. I hypothesize that SAMD1

directs transcription and signaling during hematopoiesis. To test this hypothesis, I will use in vivo and ex vivo loss-of-function approaches. First, I will perform bone marrow transplantation experiments in mice to examine the requirement of Samd1 for HSPC activity. Second, using CRISPR-Cas9, I will knock out human

SAMD1 in CD34+ hematopoietic progenitors and test SAMD1-dependent changes to the progenitor phenotype (using colony and cell signaling assays). Finally, I will establish the role of SAMD1 in modulating GATA2 gene expression using the human umbilical cord-derived erythroid progenitor-2 (HUDEP2) cell line. These

experiments will determine whether and how SAMD1 expression is needed to promote HSPC and MEP cell phenotypes, including progenitor potential, cell signaling, and transcription. Linking Samd1 function to signaling and transcriptional mechanisms opens the door to translational avenues for studying the contribution of Samd1

in hematologic pathologies. The University of Nebraska Medical Center, the parent institution of this research proposal, is rapidly developing as a biomedical research leader. The scientific environment in which the proposed studies are to be performed will directly contribute to the probability of the project’s success. UNMC

is an intellectual and collaborative environment with ample resources to facilitate training and career development. The training plan includes learning fundamental skills in the field of hematopoiesis, including hematopoietic stem cell transplantation. With the presentations, career workshops, and writing opportunities

this fellowship will provide, the career goal of becoming an expert in the field of hematopoiesis working in an academic environment will be achieved by the applicant.