Date of Award

Spring 5-15-2021

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Immunology)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

A potent immune response requires crosstalk and collaboration between the innate and adaptive immune systems, both of which contain highly specialized immune lineages. All immune lineages arise during adult life are generated from the differentiation of hematopoietic stem cells (HSCs) in the process of hematopoiesis. Normal hematopoiesis under steady state and emergency hematopoiesis during immune response are orchestrated precisely by transcriptional networks formed by transcription factors (TFs) to direct multipotent progenitors into specific fate. TFs required for the development of single or multiple lineages within the hematopoietic system has been identified, such as Irf8 for type I classical dendritic cells (cDC1s), Id2 and Nfil3 for innate lymphoid cells (ILCs), and Zeb2 for plasmacytoid dendritic cells (pDCs) and monocytes, however, how these TFs interact with each other to enforce lineage fate choices and what cis-element in their genomic locus are employed to execute such interactions and thus form regulatory networks were poorly defined.In the first part of this dissertation, we dissected the transcriptional networks involving TF Zeb2 in the fate choice of common dendritic cell progenitors (CDPs) between pDC and cDC1s. Using sc-RNA seq and several reporter mouse lines for relevant transcription factors, we identified the earliest type 1 conventional DC (cDC1) specified cells as a fraction of common dendritic cell progenitors (CDPs) marked by low expression of transcription factor Zeb2 and high expression of transcription factor Id2. We also defined a regulatory network of transcription factors involving Nfil3, Zeb2, and Id2 that controls the specification of the CDPs into a clonogenic progenitor for the cDC1 lineage. This network also imposes a switching in the usage of Irf8 enhancer. In the second part of this dissertation, we examined the molecular mechanisms governing the expression of Zeb2 across hematopoietic system, specifically how such regulation differs between fetal and adult animals. Using ATAC-seq and ChIP-seq analysis, we identified a cis-element 165kb upstream of Zeb2 transcription starting site (TSS) (-165kb Zeb2 enhancer). We generated a novel mouse model deficient in this enhancer and detected impaired Zeb2 expression throughout the hematopoietic system. We demonstrated that this enhancer and subsequently Zeb2 expression is required for the development of pDC, monocytes and B cells, the terminal maturation of NK cells under steady state, and CD8+ T cell terminal differentiation in response to acute murine LCMV infection. Surprisingly, the -165-kb Zeb2 enhancer is not required for Zeb2 expression in embryonically derived macrophage populations and their embryonic progenitors. Employing scATAC-seq technique we were able to demonstrate that the fetal-derived macrophage lineages utilize an alternative enhancer to drive Zeb2 expression. This enhancer, 164-kb downstream of Zeb2 TSS (+164-kb Zeb2 enhancer) is likely bound by TF Nur77. These discoveries provided novel insights into the precise regulation of TF expression and interactions during embryonic development and hematopoiesis.

Language

English (en)

Chair and Committee

Kenneth M. Murphy

Committee Members

Gwendalyn J. Randolph, Paul M. Allen, Takeshi Egawa, Brian T. Edelson,

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