Neural-Specific Regulation of POMC Gene Expression

描述(由申请人提供) 这次美国和阿根廷之间的Fogarty国际合作奖的竞争性续签是为了继续支持其母项目P01 DK55819“喂养和代谢的神经内分泌控制”子项目4“阿片肽对喂养和代谢的调节”中概述的科学目标。肥胖及其代谢后遗症是世界范围内的主要健康问题。阿片肽β-内啡肽和黑素皮质肽家族都是体重稳态的重要调节剂，也是同一种前激素原的产物，前阿片黑素皮质素(POMC)在下丘脑弓状核和脑干孤束核内的特定神经元群中表达。这两个大脑核团都是参与神经内分泌和自主控制食欲和摄食的复杂整合的关键区域。POMC基因的零突变很少与儿童早发性病态肥胖和过度吞噬有关。然而，在几个人类群体中的遗传学研究强烈表明POMC基因是肥胖和瘦素水平的数量性状基因座。POMC基因编码区的突变会改变肽的生产或功能，但不能解释这种联系，这表明POMC调节序列可能存在突变。我们对POMC基因神经特异性表达的分子基础知之甚少，尽管我们假设神经元POMC表达失调可能是能量平衡失调的一个因素。FIRCA项目的总体目标是阐明大脑中神经元特异性和瘦素调节的POMC基因表达的转录机制，并开发新的分子工具，进一步研究POMC多肽在食欲和摄食控制中的生理特征。将通过下列具体目标来实现这一目标：1)在转基因小鼠中利用缺失和突变分析确定POMC基因中的下丘脑神经特异性增强子(S)；2)表征POMC基因中的瘦素反应元件；以及3)通过对脊椎动物不同目的基因组元件的序列比较和对携带4.5亿年前与胎盘哺乳动物的POMC调控序列的转基因小鼠的分析，确定POMC基因的系统发育转录密码。

DESCRIPTION (provided by applicant) This competitive renewal of a Fogarty International Cooperative Award between the U.S.A. and Argentina is in continued support of the scientific goals outlined in its parent grant P01 DK55819, "Neuroendocrine Control of Feeding and Metabolism," subproject 4, "Modulation of Feeding and Metabolism by Opioid Peptides." Obesity and its metabolic sequelae are major health problems world-wide. The opioid peptide beta-endorphin and a family of melanocortin peptides are both important modulators of weight homeostasis and products of the same prohormone, proopiomelanocortin (POMC), that is expressed in specific populations of neurons within the arcuate nucleus of the hypothalamus and the nucleus tractus solitarius in the brain stem. Both of these brain nuclei are key areas involved in the complex integration of neuroendocrine and autonomic control of appetite and feeding. Null mutations of the POMC gene have rarely been associated with early onset morbid obesity and hyperphagia in children. However, genetic studies in several human populations have strongly implicated the POMC gene as a quantitative trait locus for obesity and leptin levels. Mutations in the coding region of the POMC gene that would alter peptide production or function do not account for this linkage, suggesting the alternative possibility of mutations in POMC regulatory sequences. Little is known about the molecular basis for neural-specific expression of the POMC gene, although we hypothesize that dysregulated neuronal POMC expression may be a contributing factor to disorders of energy homeostasis. The overall goal of this FIRCA project is to elucidate the transcriptional machinery responsible for neuronal-specific and leptin-regulated POMC gene expression in the brain and to develop novel molecular tools for the further physiological characterization of POMC peptides in the control of appetite and feeding. This goal will be addressed by the following specific aims: 1) Identify a hypothalamic neural-specific enhancer(s) in the POMC gene utilizing a deletional and mutational analysis in transgenic mice; 2) Characterize the leptin-responsive element in the POMC gene; and 3) Determine a phylogenetic transcriptional code for the POMC gene by sequence comparisons of genomic elements from divergent orders of vertebrate species and the analysis of transgenic mice carrying POMC regulatory sequences of Fugu rubripes, a teleost fish that diverged from placental mammals 450 million years ago.