Date of Award
5-25-2023
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Development of immune cells is orchestrated by expression of transcription factors which function to control differentiation of progenitor populations and survival of mature cells. Nonclassical monocytes are a population of myeloid cells which patrol the bloodstream and are thought to maintain vascular endothelium. Conventional dendritic cells (cDCs) are antigen-presenting myeloid cells which serve to activate naïve T cells during infections. cDCs are further differentiated into cDC1s capable of cross-presenting exogenous antigens to activate CD8 T cells and cDC2s which are thought to play essential roles in activating Th2 and Th17 responses. These disparate cells originate from a shared bone marrow population termed the monocyte-dendritic cell progenitor and must acquire distinct transcriptional profiles to perform their distinct functions. Mechanisms governing the differentiation of cDC1 and cDC2 have not been fully elucidated. The process by which nonclassical monocytes arise from classical monocytes additionally remains unclear. Previous work in cDC differentiation using germline knockout mice had revealed a contributing role of the transcription factor Bcl6 in survival and/or differentiation of cDC1s. To determine more specifically the nature of the requirement for Bcl6 in cDC1s, we crossed Bcl6flox mice to Csf1rCre mice to generate Bcl6cKO mice in which Bcl6 is conditionally ablated in myeloid cells. We surprisingly found that while Bcl6 was strictly required for in vitro development of cDC1s, cDC1 development was not abrogated in vivo. Instead, Bcl6cKO mice developed cDC1s with altered surface marker expression. These cDC1s were functional and able to support tumor rejection. Simultaneously, we examined the previously-published claim that the transcription factor Irf2 is required to support development of cDC2s. We find that Irf2-/- mice have significant reductions in cDC2s. However, Irf2-/- bone marrow gives rise to cDC2s in mixed bone marrow chimera settings, demonstrating that the effect of Irf2 on cDC2 development is not cell-intrinsic. We also investigated the roles of Bcl6 and Irf2 in nonclassical monocyte development. We found that Bcl6 and Irf2 were both required in nonclassical monocytes in a cell-intrinsic manner. To facilitate investigation of nonclassical monocytes, we created a method for development of nonclassical monocytes in vitro via activation of Notch signaling. Surprisingly, we find that Irf2 but not Bcl6 is required for in vitro differentiation of nonclassical monocytes. This work advances our understanding of mechanisms governing differentiation of cDCs and nonclassical monocytes and will support further studies exploring the development of these cells.
Language
English (en)
Chair and Committee
Kenneth Murphy
Recommended Citation
O'Connor, Kevin William, "Roles of the Transcription Factors Bcl6, IRF2, and Notch2 in Myeloid Development" (2023). Arts & Sciences Electronic Theses and Dissertations. 2986.
https://openscholarship.wustl.edu/art_sci_etds/2986