Date of Award

Fall 12-2019

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Sciences

Advisor

Jennifer Trowbridge

Second Committee Member

Derry Roopenian

Third Committee Member

Dustin Updike

Additional Committee Members

Luanne Peters

Christopher Baker

Abstract

As lifespan is increasing globally, there is a critical need to identify strategies to extend healthspan and prevent chronic diseases into older age. The long-term goal of my research is to identify novel strategies to ameliorate aging-induced decline in hematopoietic stem cell (HSC) function. HSCs give rise to all mature blood and immune cells. With age, HSCs undergo defects in their differentiation ability which correlates with a decline in immune function. Comprehensive knowledge of gene regulatory and epigenetic mechanisms underlying this defect is a barrier to developing therapies to ameliorate aging-associated decline in HSC function. Therefore, my project focuses on understanding the gene regulatory mechanisms underlying this decline in HSC function. Before delving into the gene regulatory mechanisms that go awry with age, it is important to identify which mechanisms are important for the differentiation of HSCs to mature cells. The majority of screening approaches for the identification of novel genes and gene regulatory elements rely on robust in vitro assays. In my thesis work, I have demonstrated in my thesis work that one such assay widely used in the field to differentiate hematopoietic stem and progenitor cells (HSPCs) to B-lymphoid cells performs in a qualitative rather than a quantitative manner which provides implications for interpretations of results this assay. Also, by mining publicly available gene expression data sets and data from an unpublished shRNA knockdown screen, I have identified that the epigenetic regulator lysine acetyltransferase 6b (Kat6b) is important for HSC function as well as demonstrated that KAT6B levels are significantly decreased in expression in aged long term-hematopoietic stem cells (LT-HSCs) at the transcript and protein levels, using qPCR and immunofluorescence. In addition, I have observed that knockdown of Kat6b leads to enhanced myeloid differentiation from LT-HSCs by using in vitro and in vivo assays which partially replicates aging-associated hematopoietic phenotypes. Transcriptome analysis suggests that Kat6b knockdown in LT-HSCs leads to dysregulation of differentiation signatures and an increase in inflammation. These data support increasing the levels of Kat6b as a novel therapeutic strategy for ameliorating aging-associated hematopoietic decline.

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