Date of Award
8-14-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
To provide protection against a broad spectrum of threats, the immune system must give rise to a diverse range of cell types each with specialized roles in host defense. Transcriptional regulation is achieved by interactions between transcription factors and non-coding cis-regulatory DNA elements such as promoters and enhancers. One of the most important transcription factors in lymphocyte development and function is TCF1 (encoded by the Tcf7 gene). TCF1 is required for the efficient development of both innate lymphocytes, such as NK cells, as well as adaptive T cells. TCF1 also regulates the functional abilities of these cell types, such as cytokine production, cytotoxicity, proliferation, and survival. Our lab has previously identified a TCF1 centered transcriptional network that supports proliferation and survival of naïve or memory-like lymphocytes, which upon activation is then decommissioned in favor of a BLIMP1 centered network that in turn supports the acquisition of mature effector functions. While this counter-regulatory relationship between BLIMP1 and TCF1 has been well established, the exact mechanisms controlling this balance between TCF1 and BLIMP1 expression in lymphocytes have remained unclear. To better understand how TCF1 expression is regulated, we undertook an integrative analysis of cis-regulatory elements in the Tcf7 locus. Analysis of ATAC-seq data from lymphocytes undergoing activation revealed an evolutionarily conserved non-coding sequence within an intronic region of the Tcf7 gene which, although normally inaccessible, becomes accessible during activation. Chromatin accessibility at this region appears to be inversely correlated with Tcf7 expression, suggesting it could be acting as a regulatory element. To explore what transcription factors could act upon this regulatory element, we disrupted individual transcription factor binding motifs within this conserved region. This revealed that the silencing functions of this regulatory element required a binding site for BLIMP1, a repressive transcription factor that is upregulated by inflammatory cytokine signals. Having identified this cis-regulatory element as a candidate repressor of Tcf7 expression, we then sought to confirm its function as such in vivo. To this end we generated a novel knockout mouse line which lacks this regulatory element. Indeed, we found that deleting this sequence results in an impaired ability for lymphocytes to maintain normal downregulation of Tcf7 in response to stimulation. Thus, this highly conserved cis-regulatory element appears to act as a repressor which limits Tcf7 expression in NK cells in response to activation signals.
Language
English (en)
Chair and Committee
Eugene Oltz
Committee Members
Jacqueline Payton; Marco Colonna; Takeshi Egawa; Wayne Yokoyama
Recommended Citation
McCullen, Matthew Vincent, "An Intronic Regulatory Element Limits Tcf7 Expression in Natural Killer Cells" (2024). Arts & Sciences Electronic Theses and Dissertations. 3312.
https://openscholarship.wustl.edu/art_sci_etds/3312