Hematopoietic Stem Cell Biology

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This project of the Hematopoiesis Section is focused on the basic biology of hematopoietic stem cells (HSC). HSC are a rare population of self-renewing cells that give rise to all cells in the peripheral blood. For patients with a life-threatening hematologic disease, transplantation of HSC from a healthy closely matched donor after ablation of the diseased bone marrow can be a life long cure. However, the main risk in these procedures is the transplantation of inadequate numbers of HSC. Our goal is to understand the processes that promote HSC self-renewal and inhibit HSC differentiation. By manipulating the balance between self-renewal and differentiation we will be able to increase the number of stem cells and consequently increase the effectiveness of bone marrow transplantation to cure acquired or inherited hematopoietic diseases. Specific Aim 1: We have previously used ChIP Seq to evaluate the role of EKLF (transcription factor) binding in mouse erythroid cells. We will use this same procedure to analyze DNA methylation and histone tri methylation in mouse HSC (Lin- c-kit+ Sca-1 +) multipotent progenitor cells (Lin-, c-kit+ Sca-1-) and erythroid progenitor cells (Lin-, CD71+, GlyA+). After sequencing the enriched DNA fragments, we will use the Eland software to map each sequence tag to the genome and the MACS program to determine where significant enrichment has occurred. Loci at which the methylation pattern differs between HSC and progenitor cells will be analyzed to determine the pathways associated with HSC differentiation. Similar analyses will be performed to determine what causes restriction to the erythroid lineage. Specific Aim 2: CMML is an unusual bone marrow failure syndrome with a clonal out growth of monocyte progenitors (Lin- CD33+ CD34+). This disorder id treated with the DNA methylation inhibitor 5-aza cytidine and histone deacetylase inhibitors. However, whether the effects of these drugs are specifically due to the described actions of these drugs is not known. We will perform methylation pull down and ChIPSeq on tri methylated histones on chromatin extracted from CMML monocyte progenitors before and after treatment with these drugs. We will analyze the genome wide results to determine whether the drugs cause minimal, local or global epigenetic alterations. In addition, we hope to correlate the response with a specific change, allowing a more detailed understanding of the disease process.