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于促进β细胞再生和糖尿病的治疗具有重要的意义。这笔赠款支持的研究已经确定了在生长、生理扩张和再生过程中，β细胞复制在调节β细胞质量方面的重要性。在过去的资金周期中，我们已经证明周期蛋白D2不仅在建立β细胞团方面发挥着关键作用，而且在适应胰岛素抵抗方面也发挥着关键作用。我们确定了代谢变化如何通过调节p27细胞丰度的机制来调节β细胞质量。最近，我们发现，依赖于年龄的β细胞复制能力随着年龄的增长而下降，并受到多梳基因的调控，该基因通过表观遗传机制控制细胞周期调节因子p16INK4a的水平。在接下来的五年里，我们建议设计表观遗传学策略，以增强成人的β细胞复制，测试再生损伤模型中对β细胞复制的要求，并开发新的成像工具来可视化生长、发育和再生过程中的β细胞复制。我们拟研究：目的1，体内β细胞中Ezh2水平升高是否能抑制p16INK4a，促进成年小鼠的β细胞复制，促进β细胞再生；目的2，通过建立和分析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细胞中的BRG1靶点进行全基因组分析；目的3，评估将细胞周期蛋白D2导入到周期蛋白D2基因缺失的小鼠的β细胞中，是否足以促进β细胞的生长和再生；在目标4中，建议使用一种带有荧光传感器的新型转基因小鼠系统来监测胰腺发育、出生后生长和再生过程中细胞周期动力学的时空模式。这些研究将使用空白小鼠突变体、β细胞特异性诱导转基因小鼠和培养的胰岛，使用完全在实验室实施的方法。这一提议的一个主要综合优势是，我们已经培育或获得了这里描述的所有小鼠，并评估了它们的繁殖性能，并进行了杂交，以验证我们产生所需基因类型的能力。 公共卫生相关性：由于糖尿病患者需要终生胰岛素治疗，并且有很高的医疗并发症风险，因此迫切需要预防性或根治性治疗。糖尿病是由于功能性β细胞数量不足造成的，越来越多的证据表明，β细胞的复制是β细胞适应不断变化的代谢需求和再生过程中的主要手段。这项建议认为，了解β细胞再生的机制可能有助于再生β细胞，这种方法利用生理需求导致的β细胞团扩张的机制，将对开发涉及糖尿病患者β细胞再生的新治疗方法至关重要。

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.