C/EBPb and heterochromatin: their role in adipogenesis

描述(申请人提供)：肥胖是世界上最普遍的健康问题之一，特别是如果考虑到它与相关疾病如II型糖尿病、血脂异常和高血压的发病率增加有关的话。肥胖是脂肪细胞体积增大和新脂肪细胞发育的结果。脂肪形成是一系列遗传事件的结果，其中CCAAT/增强子结合蛋白(C/EBPs)在其中起关键作用。小鼠体内C/EBP2、C/EBP4或C/EBP1基因的缺失会导致脂肪组织发育缺陷。在脂肪形成过程中，特定的一组基因被激活，其余的基因被沉默。随着基因的沉默，染色质浓缩的程度增加，DNA的延伸区域被包装成转录不活跃的形式：异染色质。将基因组织成异染色质是控制其沉默的机制之一。有趣的是，在激素刺激下，C/EBP2在异染色质中迅速重新定位。在诱导前脂肪细胞分化为脂肪细胞时，C/EBP2、C/EBP4和C/EBP1也集中在异染色质中。我们推测C/EBP2可能在调节细胞分化过程中的基因沉默中发挥作用。因此，该项目的具体目标是研究在前脂肪细胞和脂肪形成过程中：a)调节C/EBP2同源和异源二聚体形成的机制，b)控制C/EBP2亚核分布的机制，以及c)通过确定C/EBP2靶基因相对于异染色质的位置在基因表达中的作用。我们的研究将有助于理解控制C/EBPs核再分布的机制以及它们在异染色质核室中的作用。提高我们对脂肪生成的理解是重要的，因为这最终将有助于开发新的肥胖症和相关疾病的治疗策略。这项研究扩展了Piwien-Pilipuk博士提出的新方法，当时她是Schwartz博士实验室的博士后实习生。现在Piwien-Pilipuk博士已经返回阿根廷并正在建立一个独立的实验室，这些PI之间通过拟议的项目进行的合作互动，包括Piwien-Pilipuk博士和她的至少一名研究生在该项目过程中访问Schwartz博士的实验室，将促进Piwien-Pilipuk博士的职业发展，此外还将通过合作论文增加对C/EBPβ调控的理解。这项研究将主要在阿根廷布宜诺斯艾利斯的Leloir研究所进行，作为NIH Grant R01DK46072授予Schwartz博士的延伸：肥胖是世界上最普遍的健康问题之一，特别是如果它与糖尿病等相关疾病有关的话。提高我们对脂肪生成的理解最终将有助于开发新的肥胖症和相关疾病的治疗策略。

DESCRIPTION (provided by applicant): Obesity is one of the most prevalent health problems in the world, particularly if it is considered in relation to the increase in prevalence of associated diseases such as type II diabetes, dyslipemia and hypertension. Obesity is the consequence of increased adipocyte size as well as development of new fat cells. Adipogenesis results from a cascade of genetic events in which CCAAT/Enhancer Binding proteins (C/EBPs) play a key role. Disruption of the C/EBP2, C/EBP4 or C/EBP1 gene in mice causes defective development of adipose tissue. During adipogenesis the activation of a specific subset of genes and silencing of the remainder takes place. As genes are silenced, the extent of chromatin condensation increases, and extended regions of DNA are packaged in transcriptionally inactive form: heterochromatin. The organization of genes into heterochromatin is one of the mechanisms that control its silencing. Intriguingly, C/EBP2 rapidly relocalizes in heterochromatin upon hormonal stimulation. C/EBP2, C/EBP4 and C/EBP1 also concentrate in heterochromatin upon induction of preadipocytes to differentiate into adipocytes. We hypothesize that C/EBP2 may play a role in the regulation of gene silencing during cellular differentiation. Thus the specific aims of this project are to investigate in preadipocytes and during adipogenesis: a) mechanisms that regulate the formation of homo- and heterodimers of C/EBP2, b) mechanisms that control the subnuclear distribution of C/EBP2, and c) the role of C/EBP2 in gene expression by determining the position of C/EBP2 target genes with respect to heterochromatin. Our studies will provide insight into the understanding of the mechanism that controls the nuclear redistribution of C/EBPs and their role in the heterochromatic nuclear compartment. Improvement of our understanding of adipogenesis is important, for it will ultimately contribute to the development of new therapeutic strategies for obesity and related disorders. This study extends new approaches initiated by Dr. Piwien-Pilipuk when she was a postdoctoral trainee in Dr. Schwartz's lab. Now that Dr. Piwien-Pilipuk has returned to Argentina and is establishing an independent lab, the collaborative interactions between these PI's through the proposed project, involving visits to Dr. Schwartz's lab by Dr. Piwien-Pilipuk and at least one of her graduate students during the course of this project, will facilitate Dr. Piwien-Pilipuk's career development, in addition to adding to understanding of the regulation of C/EBP beta through collaborative papers. This research will be done primarily at Instituto Leloir, Buenos Aires, Argentina as an extension of NIH Grant R01DK46072 to Dr. Schwartz PUBLIC HEALTH RELEVANCE: Obesity is one of the most prevalent health problems in the world, particularly if it considered in relation to associated diseases such as diabetes. Improvement of our understanding of adipogenesis will ultimately contribute to the development of new therapeutic strategies for obesity and related disorders.