Role of B2 in Brown Fat Transcription and Development

描述（由申请人提供）：肥胖是一种与几种代谢性疾病（如2型糖尿病）相关的全球健康流行病。白色脂肪组织（WAT）积累脂肪作为能量储存，过量会导致肥胖，而棕色脂肪组织（BAT）通过非寒颤产热将能量作为热量消散。最近，大量功能性BAT已被证明存在于成年人中，这一发现引起了相当大的兴趣，因为BAT活性的增加可能对肥胖有保护作用。诱导解偶联蛋白-1 （uncoupling protein-1, UCP1）等产热基因和促进BAT发育可能是肥胖症的治疗策略。因此，阐明BAT的转录网络至关重要。我们发现了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，并且在冷暴露时急剧诱导。我们发现B2直接结合并激活UCP1启动子。假定的B2结合元件在其他bat富集基因的启动子区域被发现，我们检测到B2结合和激活PGC1¿启动子。B2在棕色脂肪细胞分化过程中表达增加。我们发现B2的组成表达促进棕色脂肪细胞分化，而shRNA敲低抑制分化。我们培养的B2基因敲除小鼠BAT质量显著降低，棕色脂肪细胞形态异常，UCP1等BAT富集基因表达减少。本研究的目的是了解B2如何激活UCP1等BAT基因，以及B2在BAT发育和功能中的作用。目的1是研究B2激活UCP1和其他bat富集基因的分子机制，以及B2在冷暴露下是如何被诱导的。目的2：探讨B2在体外棕色脂肪细胞分化中的作用。目的3是在小鼠中采用功能获得和功能丧失的方法来检测体内B2的功能。这项研究将有助于BAT生物学的新兴领域，并可能为肥胖治疗提供新的靶点。

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.