Understanding the molecular mechanisms that regulate beta cell mass have important ramifications for fostering beta cell regeneration and the treatment of diabetes. Studies supported by this grant have established the importance of beta cell replication in regulating beta cell mass during growth, physiological expansion and regeneration. During the past funding cycle, we have shown that cyclin D2 plays a key role not only in establishing beta cell mass but also in adapting to insulin resistance. We established how metabolic changes lead to modulation of beta cell mass by mechanisms that regulate the cellular abundance of p27. Recently, we have shown that the age-dependent capacity of beta cells to replicate declines with age and is regulated by polycomb genes that control the levels of cell cycle regulator, p16Ink4a by epigenetic mechanisms. In the next five years we propose to design epigenetic strategies that can enhance beta cell replication in adults, test the requirements of beta cell replication in injury models of regeneration and develop new imaging tools to visualize beta cell replication during growth, development and regeneration. We propose to study:
Aim 1, whether increased Ezh2 levels in beta cells in vivo can inhibit p16Ink4a, promote beta cell replication and enhance beta cell regeneration in adult mice;
in Aim 2, study the mechanism by which Brg1 regulates beta cell replication in vivo by generating and analyzing mice that lack Brg1 in beta cells and carry out genome-wide analysis of Brg1 targets on cell cycle regulators in beta cells;
in Aim 3, assess whether introduction of cyclin D2 into beta cells of cyclin D2 null mice is sufficient for beta cell growth and regeneration;
in Aim 4, propose to monitor the spatiotemporal patterns of cell-cycle dynamics during pancreas development, growth in postnatal period and regeneration using a novel transgenic mouse system with fluorescent sensors. These studies will be carried out using null mouse mutants, beta cell-specific inducible transgenic mice, and cultured islet, using methods that are fully implemented in the laboratory. A major overall strength of this proposal is that we have already generated or obtained all the mice described here as well as assessed their breeding performance, and have carried out intercrosses to verify our ability to generate desired genotypes.

Public Health Relevance

As diabetic patients require life-long insulin therapy and have a high risk of medical complications, preventative or curative therapies are urgently needed. Diabetes results from an inadequate mass of functional beta cells and there is increasing evidence to suggests that replication of beta cell is the dominant means by which beta cells adapt to changing metabolic demands and during regeneration. This proposal contends that understanding the mechanisms of beta cell regeneration could be useful for regenerating beta cells and such an approach that exploits the mechanisms involved in the expansion of beta cell mass due to physiologic demands will be critical in developing novel therapeutic approaches that involve beta-cell regeneration in diabetic patients.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK068763-09
Application #
8299092
Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
Program Officer
Sato, Sheryl M
Project Start
2004-07-05
Project End
2015-06-30
Budget Start
2012-07-01
Budget End
2013-06-30
Support Year
9
Fiscal Year
2012
Total Cost
$349,329
Indirect Cost
$122,492
Name
University of California Los Angeles
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
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Georgia, Senta; Kanji, Murtaza; Bhushan, Anil (2013) DNMT1 represses p53 to maintain progenitor cell survival during pancreatic organogenesis. Genes Dev 27:372-7
Kartikasari, Apriliana E R; Zhou, Josie X; Kanji, Murtaza S et al. (2013) The histone demethylase Jmjd3 sequentially associates with the transcription factors Tbx3 and Eomes to drive endoderm differentiation. EMBO J 32:1393-408
Dhawan, Sangeeta; Georgia, Senta; Tschen, Shuen-Ing et al. (2011) Pancreatic ? cell identity is maintained by DNA methylation-mediated repression of Arx. Dev Cell 20:419-29
Tschen, Shuen-Ing; Georgia, Senta; Dhawan, Sangeeta et al. (2011) Skp2 is required for incretin hormone-mediated ?-cell proliferation. Mol Endocrinol 25:2134-43
Papizan, James B; Singer, Ruth A; Tschen, Shuen-Ing et al. (2011) Nkx2.2 repressor complex regulates islet *-cell specification and prevents *-to-*-cell reprogramming. Genes Dev 25:2291-305
Georgia, Senta; Hinault, Charlotte; Kawamori, Dan et al. (2010) Cyclin D2 is essential for the compensatory beta-cell hyperplastic response to insulin resistance in rodents. Diabetes 59:987-96
Tschen, Shuen-Ing; Dhawan, Sangeeta; Gurlo, Tatyana et al. (2009) Age-dependent decline in beta-cell proliferation restricts the capacity of beta-cell regeneration in mice. Diabetes 58:1312-20
Dhawan, Sangeeta; Tschen, Shuen-Ing; Bhushan, Anil (2009) Bmi-1 regulates the Ink4a/Arf locus to control pancreatic beta-cell proliferation. Genes Dev 23:906-11
Dhawan, Sangeeta; Georgia, Senta; Bhushan, Anil (2007) Formation and regeneration of the endocrine pancreas. Curr Opin Cell Biol 19:634-45

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