CELL AND DEVELOPMENTAL BIOLOGY
Identification and characterization of MAFA coregulators: MLL3/4 and its role in mouse and human islet β-cells
David William Scoville
Dissertation under the direction of Professor Roland Stein
Pancreatic islet β-cells are critical regulators of glycemic control, and their dysfunction or absence leads to Diabetes Mellitus. Several transcription factors play crucial roles in the development of functional β-cells, including the transcription factor MafA. MafA expression is restricted to islet β-cells in the pancreas where it regulates postnatal β-cell maturation and function in the mouse. However, little is known about the mechanisms through which MafA regulates its target genes. The goal of this dissertation work was to identify coregulators which interact with and contribute to the function of the MafA transcription factor. Utilizing an unbiased proteomics approach in a mouse β-cell line, I identified several potential coregulators of MafA that could control the many activities associated with this protein, including β-cell proliferation and glucose-stimulated insulin secretion. Among them were the mixed-lineage leukemia 3 and 4 (Mll3/4) complexes, known for their role in histone 3 lysine 4 (H3K4) methylation and gene activation. MafA was bound to the Mll3/4 complexes in experiments performed with size fractionated β-cell extracts and by immunoprecipitation analysis. Likewise, the MLL3 and MLL4 complexes bound human MAFB, which is closely related to MAFA, important to mouse β-cell development, and co-produced with MAFA in adult human islet β-cells. Knockdown of NCOA6, a core subunit of these methyltransferases, reduced expression of only a small subset of MAFA and MAFB target genes in mouse and human β-cell lines. In contrast, a more profound effect on MafA/MafB gene activation was observed upon NCoA6 deletion specifically in embryonic β-cells using rat insulin promoter-driven Cre. We propose that this broader impact is due to the coordinated recruitment of the Mll3/4 complexes by MafB during development and MafA postnatally. Future studies may elucidate the context-dependent mechanisms involved in regulating MAFA and MAFB coregulator binding. This may allow for development of therapeutic strategies for enhancing β-cell function and mass in the treatment of diabetes.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-07172015-124218 |
| Date | 23 July 2015 |
| Creators | Scoville, David William |
| Contributors | Maureen Gannon, Guoqiang Gu, Alvin Powers, Peter A. Weil |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-07172015-124218/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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