Role of B2 in Brown Fat Transcription and Development

描述(申请人提供)：肥胖是一种全球性的健康流行病，与几种代谢性疾病有关，如2型糖尿病。白色脂肪组织(Wat)积累脂肪作为能量储存，过量导致肥胖，而棕色脂肪组织(BAT)通过非颤抖的产热作用将能量作为热量散失。最近，大量的功能性蝙蝠已被证明即使在成年人身上也存在--这一发现引起了人们的极大兴趣，因为蝙蝠活动的增加可能会预防肥胖。诱导解偶联蛋白-1(UCP1)等生热基因和促进BAT发育可能是治疗肥胖症的策略。因此，阐明BAT转录网络是至关重要的。我们已经鉴定出一种新的锌指转录因子B2，与WAT和其他组织相比，它在BAT中优先表达，并且在冷暴露时被强烈诱导。我们发现B2直接与UCP1启动子结合，并强烈激活UCP1启动子。在其他BAT富集型基因的启动子区域中发现了可能的B2结合元件，并且我们检测到B2与PGC1启动子的结合和激活。在棕色脂肪细胞分化过程中，B2的表达增加。我们发现B2的结构性表达促进了棕色脂肪细胞的分化，而shRNA敲除则抑制了分化。我们产生的B2基因敲除小鼠表现出显著的BAT质量减少和异常的棕色脂肪细胞形态，以及UCP1和其他富含BAT的基因的表达减少。本研究的目的是了解B2是如何激活UCP1和其他蝙蝠基因的，以及B2在蝙蝠发育和功能中的作用。目的1是研究UCP1和其他富含蝙蝠的基因激活B2的分子机制，以及在冷暴露下B2是如何被诱导的。目的2探讨B2在棕色脂肪细胞体外分化中的作用。目的3是利用小鼠的功能获得和功能丧失的方法来检测B2在体内的功能。这项研究将有助于蝙蝠生物学的新兴领域，并可能为肥胖症治疗提供新的靶点。

DESCRIPTION (provided by applicant): Obesity is a global health epidemic associated with several metabolic diseases, such as type 2 diabetes. While white adipose tissue (WAT) accumulates fat as energy storage that in excess results in obesity, brown adipose tissue (BAT) dissipates energy as heat via non-shivering thermogenesis. Recently, substantial functional BAT has been proven to be present even in adult humans-a finding which has generated considerable interest, since an increase in BAT activity may be protective against obesity. Inducing thermogenic genes such as uncoupling protein-1 (UCP1) and promoting BAT development could be therapeutic strategies for obesity. Thus, it is critical to elucidate the BAT transcriptional network. We have identified a novel zinc finger transcription factor, B2, which is preferentially expressed in BAT compared to WAT and other tissues and is induced drastically upon cold exposure. We found that B2 directly binds to and robustly activates the UCP1 promoter. The putative B2 binding element is found in the promoter regions of other BAT-enriched genes, and we detected binding and activation of PGC1¿ promoter by B2. B2 expression is increased during brown adipocyte differentiation. We found that constitutive expression of B2 enhances brown adipocyte differentiation, whereas shRNA knockdown inhibits differentiation. The B2 knockout mice that we have generated show drastically decreased BAT mass with abnormal brown adipocyte morphology and decreased expression of UCP1 and other BAT-enriched genes. The goal of this research is to understand how B2 activates UCP1 and other BAT genes and the role of B2 in the BAT development and function. Aim 1 is to examine the molecular mechanisms underlying B2 activation of UCP1 and other BAT-enriched genes and how B2 is induced upon cold exposure. Aim 2 is to investigate the role of B2 in brown adipocyte differentiation in vitro. Aim 3 is to employ gain- and loss-of function approaches in mice to examine the function of B2 in vivo. This research will contribute to the emerging field of BAT biology and may provide new targets for obesity therapeutics.