Transcriptional Regulation of Pancreatic Beta Cell Mass

描述(由申请人提供)： 2型糖尿病是一种影响超过2500万美国人(或超过8%的人口)的疾病。随着肥胖率的增加，我们看到2型糖尿病的发病率也随之增加。退伍军人的糖尿病患病率明显高于普通人群，而且还在继续上升。越来越多的人认识到，2型糖尿病的一个关键缺陷是胰岛β细胞无法产生足够的胰岛素来满足胰岛素抵抗的需求。了解控制胰岛细胞增殖的正常生理机制可以帮助我们开发靶向疗法，帮助维持和扩大功能性的胰岛细胞群。我们已经使用肥胖的小鼠模型来识别参与调节β细胞适应性增殖反应的基因，观察对增加的胰岛素需求的自然适应性反应为确定β细胞复制机制提供了一个有用的工具。利用这个模型，我们已经确定了一个新的转录因子tcf19，它与小鼠胰岛的增殖反应高度相关。Tcf19基因在很大程度上尚未确定，但已知是一个细胞周期调控基因。我们的初步结果表明，tcf19在β细胞中表达，并且是β细胞所必需的。 成长和生存。我们推测，tcf19是β细胞复制的关键转录调节因子，也在调节内质网应激反应基因以防止细胞凋亡方面发挥重要作用。在这项提案中，我们将研究tcf19在β细胞中的转录活性。 用染色质免疫沉淀法鉴定tcf19的直接转录靶点。具体地说，我们将寻找关键细胞周期和ER伴侣基因的调节，以了解TCF19对细胞生长影响的机制。接下来，我们将使用腺病毒表达系统来确定tcf19是否足以促进小鼠和人类胰岛的细胞增殖和保护细胞免于凋亡。我们还将进一步研究tcf19对人类胰岛转录的影响。最后，我们将产生并鉴定tcf19的细胞特异性敲除，以确认它是细胞在体内扩张和存活所必需的。在完成拟议的研究后，我们将清楚地了解这种新型的细胞质量调节因子的作用。最终，我们的目标是清楚地阐明调控的途径。 细胞增殖和存活是增加细胞质量的一种手段。如果我们能够在胰岛素抵抗的情况下增加细胞量，我们将能够防止高危人群发生2型糖尿病，并改进对已经患有糖尿病的人的治疗。

DESCRIPTION (provided by applicant): Type 2 diabetes is a disease that affects more than 25 million Americans (or over 8% of the population). As rates of obesity increase, we see concomitant increases in rates of type 2 diabetes. The prevalence of diabetes is significantly higher in Veterans than in the general population and also continues to rise. It is increasingly recognized that a key defect in type 2 diabetes is failure of the pancreatic beta cells to produce enough insulin to keep up with the demands of insulin resistance. Gaining an understanding of the normal physiologic mechanisms that control beta cell proliferation can allow us to develop targeted therapeutics that can help maintain and expand functional beta cell mass. We have used a mouse model of obesity to identify genes that are involved in regulating the adaptive proliferative response of the beta cell Looking at the natural adaptive responses to increased insulin demand provides a useful tool to identify mechanisms of beta cell replication. Using this model, we have identified a novel transcription factor, tcf19, which is highly correlated with the proliferative response in mouse islets. Tcf19 is largely uncharacterized, but is known to be a cell cycle regulated gene. Our preliminary results indicate that tcf19 is expressed in the beta cell and is required for beta cell growth and survival. We hypothesize that tcf19 is a key transcriptional regulator of beta cell replication and is also important in the regulation of ER stress response genes to prevent apoptosis. In this proposal, we will examine the transcriptional activity of tcf19 in the beta cell using chromatin immunoprecipitation to identify direct transcriptional targets of tcf19. Specifically, we will look for regulation of key cell cycle and ER chaperone genes to understand the mechanism for the effects of tcf19 on ¿-cell growth. We will next use an adenoviral expression system to determine if tcf19 is sufficient to promote ¿-cell proliferation and protect from ¿-cell apoptosis in mouse and human islets. We will also further examine the effects of tcf19 on transcription in human islets. Finally, we will generate and characterize a ¿-cell specifi knockout of tcf19 to confirm that it is necessary for ¿-cell expansion and survival in vivo. Upon completion of the proposed studies, we will have a clear understanding of the role of this novel regulator of ¿-cell mass. Ultimately, our goal is to clearly elucidate the pathways that regulate ¿ cell proliferation and survival as a means to increase ¿-cell mass. If we are able to increase ¿-cell mass in the face of insulin resistance, we will be able to prevent the onset of type 2 diabete in those at high risk and improve treatment for individuals already suffering from diabetes.