Dissecting Adipose Depot-Selective Regulation of Gene Programs

描述（由申请人提供）：该申请涉及广泛的挑战领域（15）转化科学和特定的挑战主题，15- dk -102：开发改进的NIDDK疾病动物模型。在过去的几年里，许多实验室的工作都强调了身体内不同的脂肪库不仅在解剖位置上是不同的，而且在相对独特的基因表达程序上也是不同的。虽然在决定成熟脂肪细胞功能的基因方面存在许多重叠，但同样清楚的是，不同的脂肪垫表达独特的基因表达亚群，导致生理上不同的脂肪组织。我们的最终目标是理解和操纵不同脂肪垫中作为不同基因簇的基因表达，这些基因簇在整个基因簇的水平上被操纵，而不是在单个基因的水平上。在这里，Stephen Farmer和Philipp Scherer的实验室已经联合起来，汇集他们的专业知识和资源来解决我们认为是脂肪组织生物学中最重要的问题之一，脂肪垫特异性基因表达的分子基础。我们的假设是，这些程序（而不是单个基因）以一种特定的方式被脂肪垫调节，并负责个体脂肪垫的独特特征。棕色脂肪组织在成人中的重要性在最近的过去获得了一些新的兴趣。参与“白色脂肪细胞褐变”的关键因素已经确定，但仍有待进一步研究。调控棕色脂肪细胞程序的关键因素之一是PRDM16。关于prdm16介导的基因表达的模块化性质，还有很多有待研究。因此，我们提出解决模块化的脂肪垫特异性基因表达控制问题，目的如下：SA1: PPARg在不同脂肪垫中的作用是什么，它如何实现脂肪垫特异性基因表达？PPARg通过与多种协同抑制因子和协同激活因子的不同关联诱导脂肪垫特异性作用。定义螺旋7的突变使Farmer小组能够以独特的方式操纵PPARg活性，现在可以在体内进行测试。SA2: C/EBPa在成熟脂肪细胞中的作用是什么？C/EBPa已被系统性淘汰。这导致了一种相当复杂的表型，对发育有着深远的影响。利用我们的新技术，我们将能够首次选择性地研究C/EBPa在成熟脂肪组织中的作用，而不依赖于对肝脏和脂肪形成的影响。SA3: CtBP-1和-2在白色脂肪细胞中的确切作用是什么？与它们在棕色脂肪组织中的作用相比，这种作用在不同的白色脂肪垫中的作用有何不同？CtBP-1和-2是共同抑制因子，负责关闭内脏白色基因以响应PPARg配体，但它们也是棕色脂肪组织中与PRDM16相互作用的抑制因子。选择性地、有针对性地激活这些转录程序，使脂肪垫能够在不伴有炎症的情况下扩张，这是改善肥胖相关代谢功能障碍风险的关键。

DESCRIPTION (provided by applicant): This application addresses broad Challenge Area (15) Translational Science and specific Challenge Topic, 15-DK-102: Develop improved animal models of NIDDK diseases. Work from many laboratories over the last several years has highlighted different fat depots within the body being not only distinct by anatomical location, but also characterized by relatively unique gene expression programs. While a lot of overlap exists with respect to genes that dictate mature adipocyte function, is also clear that distinct fat pads express unique subsets of gene expression resulting in physiologically distinct adipose tissues. Our ultimate goal is to understand and manipulate gene expression in distinct fat pads as distinct clusters of genes that are manipulated at the level of entire clusters rather than at the level of the individual gene. Here, the laboratories of Stephen Farmer and Philipp Scherer have teamed up to pool their expertise and resources to address what we consider to be one of the most important questions in adipose tissue biology, the molecular basis for fat pad-specific gene expression. Our hypothesis is that these programs (and not individual genes) are being modulated in a fat pad specific way and are responsible for the unique characteristics of individual fat pads. The importance of brown adipose tissue in the adult human has garnered some renewed interest in the very recent past. Critical factors involved in the "browning of white adipocytes" have been identified, but remain to be further studied. One of these critical factors that modulate portions of a brown adipocyte program is PRDM16. Much remains to be learned about the modular nature of PRDM16-mediated gene expression. Therefore, we propose to address the issue of modular, fat pad-specific control of gene expression with the following here aims: SA1: What is the role of PPARg in different pads and how does it achieve fat pad specific gene expression? PPARg induces fat pad specific effects through differential association with a multitude of co-repressors and co-activators. Defining a mutation in helix 7 has enabled the Farmer group to manipulate PPARg activity in unique ways that can now be tested in vivo. SA2: What is the role of C/EBPa in the mature adipocyte? C/EBPa has been knocked out systemically. This causes a fairly complex phenotype that has profound implications on development. Using our novel techniques, we will be able to study for the first time the role of C/EBPa in mature adipose tissue selectively, independent of effects in the liver and on adipogenesis.SA3: What is the exact role of CtBP-1 and -2 in white adipocytes and how does this action differ in distinct white fat pads compared to their role in brown adipose tissue. CtBP-1 and -2 are co-repressors responsible for turning off the visceral white genes in response to PPARg ligands but they are also the repressors interacting with PRDM16 in brown adipose tissue. The selective, targeted activation of these transcriptional programs enabling a fat pad to expand without concomitant inflammation is key to improvements of the obesity-associated risks of metabolic dysfunction. PUBLIC HEALTH RELEVANCE: Understanding and manipulating gene expression in distinct fat pads as distinct clusters of genes remains a major challenge. We propose that the physiological properties of a given fat pad are the result of the discrete regulation of a relatively small number of modules that controlled at the level of entire clusters rather than at the level of the individual genes. In this proposal, a group of investigators with expertise in the in vitro analysis of transcriptional events (Steven Farmer, Boston University) has teamed up with a group with ample expertise in the generation of mouse models (Phil Scherer, UTSW, Dallas) in which these modules will be manipulated through targeted expression or elimination of these key transcription factors.