Control of Islet Beta Specific PDX-1 and MafA Transcription

描述(申请人提供)：胰腺十二指肠同源框1(Pdx1)基因编码一种转录因子(Tf)，它在早期胰腺发育以及后来胰岛细胞的形成、维持和活动中都是必不可少的。我们已经证明，Pdx1在胰腺前体细胞和分化的细胞中的转录是由区域I、II、III和IV定义的保守的5‘侧翼序列驱动的，在小鼠中，I-II-III区域的完全缺失会导致严重的胰腺发育不良，类似于整体Pdx1基因敲除。我们有强有力的证据表明，哺乳动物专属区域II是该区域的功能核心。第二区的表观遗传结构将与基因的控制区进行比较，后者直接受 Pdx1蛋白。区域II被预测包含稳定的表观遗传结构，在产生少量Pdx1(称为Pdx1LO)的胚胎祖细胞中，Pdx1随后被修饰为细胞形成、分化和成熟细胞功能所需的高Pdx1(Pdx1HI)产生的先决条件。此外，我们将确定新发现的正性和负性作用区域II因子如何影响细胞。引人注目的是，尽管转录和染色质修饰网络对功能性细胞的生产至关重要，但这些网络是如何相互作用的还不清楚，特别是哪些共同调节因子被招募来重塑胰腺内的染色质。我们将检验这一假设，即我们新发现的Pdx1的共同调节因子深刻影响Pdx1介导的基因控制。这些发现将为转录调控机制提供有价值的见解，这些机制将在糖尿病治疗的细胞疗法的生产中有效，例如通过前向分化或重新编程。 公共卫生相关性：几项候选和全基因组研究已经确定了2型糖尿病的风险基因；这些基因包括许多与细胞发育和功能控制有关的转录因子。值得注意的是，Pdx1转录因子是年轻基因中唯一的成熟发作性糖尿病，在该基因中，纯合子突变的人有胰腺发育不全，而杂合子由于胰岛细胞功能障碍而发展为早发性糖尿病。我们建议的研究旨在确定Pdx1及其相关辅助调节因子影响细胞成熟和成体细胞功能的潜在转录机制。我们相信，我们的发现将对正在进行的从ES、iPS和/或成人细胞来源产生用于治疗1型糖尿病的细胞的努力至关重要。

DESCRIPTION (provided by applicant): The pancreatic duodenal homeobox 1 (Pdx1) gene encodes a transcription factor (TF) that is essential in early pancreas development and later in the formation, maintenance and activity of islet ¿-cells. We have shown that Pdx1 transcription in pancreatic progenitors and differentiated ¿-cells is driven by conserved 5'-flanking sequences defined by Areas I, II, III and IV, and that complete deletion of Areas I-II-III in mice causes severe pancreas hypoplasia, similar to the global Pdx1 gene knockout. We have strong evidence that mammal-specific Area II is the functional core of this region. The epigenetic architecture of Area II will be compared to control regions in genes that are directly regulated by the Pdx1 protein. Area II is predicted to contain a poised epigenetic architecture in embryonic progenitors that produce little Pdx1 (termed Pdx1LO), which is subsequently modified as a prerequisite to high Pdx1 (Pdx1HI) production required for ¿-cell formation, differentiation and mature cell function. Moreover, we will determine how newly identified positive- and negative-acting Area II TFs impact ¿-cells. Strikingly, while transcriptional and chromatin-modifying networks are critical for functional ¿-cell production, it is unclear how these networks interact, and specifically what coregulators are recruited to remodel chromatin within the pancreas. We will test the hypothesis that our newly identified coregulators of Pdx1 profoundly influence Pdx1-mediated gene control. These findings will provide valuable insight into the transcriptional regulatory mechanisms that will be effective in the production of cellular therapeutics for diabetes treatment, for example by forward directed differentiation or reprogramming. PUBLIC HEALTH RELEVANCE: Several candidate and genome-wide studies have identified risk loci for type 2 diabetes; these genes include many transcription factors implicated in the control of ¿-cell development and function. Strikingly, the Pdx1 transcription factor is the only maturity onset diabetes of the young gene in which homozygous mutant humans have pancreatic agenesis, while heterozygotes develop early-onset diabetes due to islet ¿-cell dysfunction. Our proposed studies are designed to define the underlying transcriptional mechanisms through which Pdx1 and its associated coregulators influence ¿-cell maturation and adult cell function. We believe that our findings will be essential to the ongoing efforts to generate ¿-cells from ES, iPS and/or adult cell sources for type 1 diabetes treatment.