Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Microbiology and Immunology

Collaborative Specialization

Developmental Biology

Supervisor

DeKoter, Rodney P.

Abstract

Spi-C is an E26 transformation-specific transcription factor closely related to PU.1 and Spi-B. Spi-C has lineage-instructive functions important in antibody-generating responses, B cell development, and red pulp macrophage generation. Spi-C is inducible by heme- and NF-κB-dependent pathways in macrophages. The present research aimed to examine the regulation of Spi-C in B cells. RT-qPCR revealed that Spic expression was reduced in B cells following addition of lipopolysaccharide, anti-IgM antibodies, CD40L, or cytokines BAFF+IL-4+IL-5. Blocking proliferative signaling partially prevented downregulation of Spic. Unstimulated B cells upregulated Spic over time. To determine the mechanism of Spic regulation, we examined the Spic promoter and regulatory elements. The Spic promoter had unidirectional activity, which was reduced by mutation of a predicted NF-κB binding site. Bach2 and Spi-C formed a negative regulatory loop, repressing transcription of one another. Taken together, these data indicate that Spi-C is dynamically regulated by external signals in B cells.

Summary for Lay Audience

Immune cell fate decisions are important for generating the cells that protect the body from invading pathogens. One cell type that contributes to immune responses by detecting dangerous stimuli and producing antibodies is the B cell, which can aid in the elimination of threats such as bacteria, viruses, and parasites. The development and differentiation of B cells into antibody-secreting cells relies heavily on the actions of transcription factors, including the E26-transformation-specific factors PU.1, Spi-B, and Spi-C. While PU.1 and Spi-B have well-defined roles in B cell fate decisions, the contributions and regulation of Spi-C in B cells are largely unknown. The goal of my thesis was to investigate the regulation of Spi-C in B cells and determine the biological implications of its up- or downregulation.

Gene expression analysis revealed that Spic expression was decreased when B cells were treated with signals that cause cell division. Blocking cell division partially prevented the downregulation of Spic. B cells cultured without any growth factors upregulated Spic over time. To determine how Spic is regulated, we examined the gene sequences responsible for its up- or downregulation. We identified several transcription factors that altered the expression of Spi-C by interacting with its regulatory gene sequences, including one factor known to be important in B cell fate decisions. Overall, our findings indicate that Spi-C is dynamically regulated by external signals, acting to contribute to important B cell fate decisions necessary for a robust immune system.

Available for download on Tuesday, August 01, 2023

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