Cell Cycle Control Of Beta Cell Mass

描述（由申请人提供）：了解调节β细胞质量的分子机制对促进β细胞再生和糖尿病治疗具有重要影响。该基金支持的研究已经确立了β细胞复制在生长、生理扩张和再生过程中调节β细胞质量的重要性。在过去的资助周期中，我们已经证明周期蛋白D2不仅在建立β细胞质量中起关键作用，而且在适应胰岛素抵抗中也起关键作用。我们确定了代谢变化如何通过调节p27细胞丰度的机制导致β细胞质量的调节。最近，我们发现β细胞的年龄依赖性复制能力随着年龄的增长而下降，并受多梳基因的调控，多梳基因通过表观遗传机制控制细胞周期调节剂p16Ink4a的水平。在接下来的5年里，我们建议设计表观遗传策略来增强β细胞在成人中的复制，测试β细胞在再生损伤模型中的复制需求，并开发新的成像工具来可视化β细胞在生长、发育和再生过程中的复制。我们拟研究：目的1，体内β细胞中Ezh2水平升高是否能抑制成年小鼠p16Ink4a，促进β细胞复制，增强β细胞再生；在Aim 2中，通过生成和分析β细胞中缺乏Brg1的小鼠，研究Brg1在体内调控β细胞复制的机制，并对β细胞中Brg1对细胞周期调节因子的靶点进行全基因组分析；在Aim 3中，评估将cyclin D2引入到缺乏cyclin D2小鼠的β细胞中是否足以促进β细胞的生长和再生；在Aim 4中，提出使用一种新型的带有荧光传感器的转基因小鼠系统来监测胰腺发育、产后生长和再生过程中细胞周期动力学的时空模式。这些研究将使用零小鼠突变体、β细胞特异性诱导转基因小鼠和培养的胰岛进行，使用在实验室中完全实施的方法。这个提议的一个主要的总体优势是，我们已经产生或获得了这里描述的所有小鼠，并评估了它们的繁殖性能，并进行了交叉杂交以验证我们产生所需基因型的能力。

DESCRIPTION (provided by applicant): 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.