Hypothalamic miRNAs in the Pathogenesis of Obesity

 描述(申请人提供)：肥胖症和相关疾病，如II型糖尿病的日益流行是一个主要的健康问题，特别是在儿童中。最近的证据表明，肥胖和相关疾病可能是参与能量平衡调节的各种系统发育过程改变的结果，包括下丘脑黑素皮质素系统。这个神经系统包括产生前阿片黑素皮质素(POMC)衍生多肽的神经元，是能量平衡的主要负调节因素。POMC神经元在胚胎时期开始获得其独特的特性。值得注意的是，细胞谱系实验表明，在成年小鼠中，表达Pomc的胚胎前体亚群随后采用NPY表型(一种在ARH神经元中也表达的促食欲素多肽)。然而，POMC神经元在发育过程中分化和细胞命运指定的分子机制仍然很大程度上是未知的。MicroRNAs(MiRNAs)最近已成为大脑发育的关键调节因子。这些非编码的内源性小分子在基因调控中具有重要的功能，miRNA的异常成熟会损害神经元的分化，诱导细胞死亡，破坏轴突的生长。这一设想的总体假设是，POMC神经元的正常发育需要miRNAs，而在关键的胎儿时期，特定的miRNAs的丢失会导致POMC神经元的异常成熟和长期的代谢失调。我们将使用神经解剖学、神经生理学、生理学和分子生物学的方法来验证这一假说，具体目的如下。具体目标1.我们将评估在未成熟的POMC神经元群体中，miRNA成熟在细胞命运决定中的重要性。为此，我们将建立在POMC神经元中缺失DICER(miRNA成熟所必需的酶)的小鼠模型。我们假设，在缺乏足够的miRNA成熟的情况下，表达POMC的祖细胞可能获得了非POMC表型(例如NPY表型)。我们还将研究DICER缺失对POMC和POMC→神经肽Y神经元连接性的影响。具体目的2.我们将使用体内基因沉默的方法来表征miR-103和miR-107的作用，特别是在胚胎发育过程中POMC神经元及时成熟的过程中。我们还将探讨胚胎miR-103和miR-107在POMC神经元中的表达对POMC神经元活性和连通性的重要性，以及对终身能量平衡调节和葡萄糖稳态的重要性。具体目的3。此外，我们将研究miR103/107在肥胖母鼠后代中观察到的代谢和神经解剖学缺陷中的作用。总而言之，这项工作将确定特定miRNAs在参与终生能量平衡调节的神经系统发展中的关键作用。这些研究还可能为产前营养环境的变化导致后代肥胖和糖尿病的分子机制提供新的见解，从而产生新的治疗机会。

 DESCRIPTION (provided by applicant): The growing prevalence of obesity and associated diseases, such as type II diabetes is a major health concern, particularly among children. Recent evidence has shown that obesity and related diseases might be a consequence of alterations in the developmental processes of a variety of systems involved in energy balance regulation, including the hypothalamic melanocortin system. This neural system, which includes neurons that produce pro-opiomelanocortin (POMC)-derived peptides, is a major negative regulator of energy balance. POMC neurons begin to acquire their unique properties during embryonic life. Notably, cell lineage experiments have shown that a subpopulation of embryonic Pomc-expressing precursors subsequently adopts a NPY phenotype (an orexigenic peptide also expressed in ARH neurons) in adult mice. However, the molecular mechanisms underlying the differentiation and cell fate specification of POMC neurons during development remain largely unknown. MicroRNAs (miRNAs) have recently emerged as critical regulators of brain development. These non-coding small endogenous RNA molecules have important functions in gene regulation and abnormal miRNA maturation impairs neuronal differentiation, induces cell death, and disrupts axon growth. The overall hypothesis of this proposal is that miRNAs are required for the normal development of POMC neurons and that the loss of specific miRNAs during critical fetal periods results in the abnormal maturation of POMC neurons and long-term metabolic dysregulation. Neuroanatomical, neurophysiological, physiological, and molecular approaches will be used to test this hypothesis by addressing the following specific aims. Specific Aim 1. We will evaluate the importance of miRNA maturation in cell fate decision in an immature population of POMC neurons. To this aim, we will generate mouse models in which Dicer (an essential enzyme for miRNA maturation) is deleted in POMC neurons. We hypothesize is that Pomc-expressing progenitors might acquire a non-POMC phenotype (for example a NPY phenotype) in the absence of sufficient miRNA maturation. We will also examine the impact of Dicer deletion on the connectivity of POMC and Pomc → NPY neurons. Specific Aim 2. We will use an in vivo gene silencing approach to characterize the role of miR-103 and miR-107, specifically, in the timely maturation of POMC neurons during embryogenesis. We will also explore the importance of embryonic miR-103 and miR-107 expression in POMC neurons on POMC neuronal activity and connectivity and on lifelong energy balance regulation and glucose homeostasis. Specific Aim 3. Moreover, we will examine the role of miR103/107 in the metabolic and neuroanatomical defects observed in offspring of obese dams. Together, this work will define a critical role for specific miRNAs in the development of neural systems that are involved in lifelong energy balance regulation. These studies might also provide new insight into the molecular mechanisms by which alterations of the prenatal nutritional environment lead to obesity and diabetes in the offspring, thereby generating new therapeutic opportunities.