Date of Award

Spring 2022

Project Type

Thesis

Program or Major

Biochemistry

First Advisor

Sherine F Elsawa

Second Advisor

Xuanmao Chen

Third Advisor

Sarah Walker

Abstract

B cells are an important part of the host defense against pathogens by secreting immunoglobulins (Igs)/antibodies (Abs). Igs are highly specialized molecules due to a DNA recombination process that occurs to generate the variable region. An Ab molecule also undergoes class switch recombination (CSR) after encountering an antigen. Our lab has shown that the transcription factor GLI2 can regulate IgM secretion in immortalized malignant B cells derived from Waldenström macroglobulinemia (WM) patients and can modulate several cytokines. However, if GLI2 plays a role in B cell biology and class switch recombination is unknown. In mice with a B cell-specific Gli2-deficiency (B-Gli2-/-) using CD19-cre mediated recombination, the role of Gli2 in B-2 cell biology can be studied. We found that Gli2 deletion in B cells does not affect overall mouse survival patterns or splenic B cell development. However, we found that Gli2 deletion in B cells results in increased expression of AID, an important protein in CSR. Previous lab data suggests that GLI2 may modulate class switching from IgM to IgG. A CSR assay using purified B cells from B-Gli2-/- mice showed an increase in CSR to IgG1 isotype compared to WT. Interestingly, the difference was dominantly in female mice. While CSR naturally occurs in the majority of B cells, this process is lacking in WM B cells. To address this lack of response in WM cells, cells were stimulated with CD40L + IL-4 to induce CSR and the GLI inhibitor, GANT61, was added to determine the role of GLI in CSR. I found that inhibition of GLI in the presence of CD40L + IL-4 resulted in an increase in surface IgG expression. Furthermore, there was an increase in I-C germ-line transcript (GLT) expression in WM cells treated with GANT61 further supporting the notion that GLI inhibition allows CSR to IgG. Altogether, Gli2 affects CSR in both normal B cells and WM cell lines.

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