Cyclin D2 Regulation Of Islet Growth

描述(由申请人提供)： 作为一名内科科学家，我的目标是通过研究糖尿病的病理生理学来改善儿童的生活。为此，我在过去的几年里一直在莫里斯·怀特博士的实验室里接受培训，研究糖尿病中β细胞功能障碍的病因。这项提议将使我能够在我过渡到乔斯林糖尿病中心独立资助的研究人员的职业生涯时，进一步接受细胞生物学和生理学方面的培训。 尽管胰岛素样生长因子(IGF)、其他生长因子和胰腺转录因子Pdx1可能在其中发挥作用，但对β细胞增殖的调控知之甚少。胰岛素受体底物(IRS)-2相关通路对胰岛β细胞的存活至关重要：IRS2基因敲除(-/-)小鼠发生胰岛细胞衰竭和胰岛素抵抗，导致糖尿病死亡。我之前已经证明，Irs2信号改变了Pdx1的水平，Pdx1是一种促进β细胞质量和功能的胰腺转录因子。我还发现，Pdx1的过度表达可以刺激小鼠的β细胞增殖，这是通过将BrdU掺入β细胞来衡量的。在大多数组织中，有丝分裂刺激会增加G1、Cyclin、D型细胞周期蛋白的基因表达，它们与细胞周期蛋白依赖性激酶(CDK)-4或-6配对，以促进细胞生长。值得注意的是，CDK4-/-小鼠由于β细胞生长不足而患上糖尿病。根据这些发现，我怀疑其中一个D型细胞周期蛋白可能是CDK4在胰岛扩张中的一个重要伙伴。支持这一观点的我最近发现，细胞周期蛋白D2-/-小鼠患上糖尿病并伴有β细胞生长受损。进一步的实验表明，Pdx1可以通过直接与细胞周期蛋白D2启动子结合来调节β细胞的增殖。这项提议将检验这样一种假设，即细胞周期蛋白D2对正常胰岛生长是必不可少的，而Pdx1通过检测以下特定目的来调节细胞周期蛋白D2的活性，从而调节β细胞的增殖： 1.检测细胞周期蛋白D2是否为胰岛生长的重要调节因子。 2.检测Pdx1是否通过调节细胞周期蛋白D2影响胰岛β细胞增殖。

DESCRIPTION (provided by applicant): My goal as a physician-scientist is to improve the lives of children through research on the pathophysiology of diabetes mellitus. To this end I have spent the past several years training in the laboratory of Dr Morris White investigating the etiology of beta-cell dysfunction in diabetes. This proposal will allow me to further train in cell biology and physiology as I transition to a career as an independently funded investigator in the Joslin Diabetes Center. Little is known about the regulation of beta-cell proliferation, although the insulin-like growth factors (IGFs), other growth factors, and the pancreatic transcription factor Pdx1 may play a role. Insulin Receptor Substrate (IRS)-2 related pathways are essential for beta-cell survival: Irs2 knockout (-/-) mice develop beta-cell failure and insulin resistance resulting in death from diabetes. I have previously shown that Irs2 signaling alters levels of Pdx1, a pancreatic transcription factor that promotes beta-cell mass and function. I also found that Pdx1 overexpression can stimulate beta-cell proliferation in mice, as measured by BrdU incorporation into beta-cells. In most tissues mitogenic stimuli increase gene expression of G1 cyclin D-type cyclins, which partner with cyclin dependent kinase (cdk)-4 or -6 to promote cell growth. Remarkably, cdk4-/- mice develop diabetes from inadequate beta-cell growth. From these findings I suspected that one of the D-type cyclins might be an important partner of cdk4 in islet expansion. Supporting this notion I have recently found that cyclin D2-/- mice develop diabetes with impaired beta-cell growth. Further experiments suggest that Pdx1 could regulate beta-cell proliferation by directly binding to the cyclin D2 promoter. This proposal will test the hypothesis that cyclin D2 is essential for normal islet growth and that Pdx1 regulates beta-cell proliferation by regulating cyclin D2 activity by examining the following specific aims: 1. To test if cyclin D2 is an essential regulator of islet growth. 2. To test if Pdx1 influences beta-cell proliferation by regulating cyclin D2.