Hypothalamic miRNAs in the Pathogenesis of Obesity

 描述（由申请人提供）：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，肥胖症和相关疾病可能是一个后果，在发育过程中的各种系统参与能量平衡调节，包括下丘脑黑皮质素系统的变化。该神经系统包括产生前阿黑皮素（POMC）衍生肽的神经元，是能量平衡的主要负调节因子。POMC神经元开始获得其独特的性能在胚胎生活。值得注意的是，细胞谱系实验已经表明，胚胎Pomc表达前体的亚群随后在成年小鼠中采用NPY表型（也在ARH神经元中表达的食欲肽）。然而，POMC神经元在发育过程中的分化和细胞命运规范的分子机制在很大程度上仍然未知。microRNAs（miRNAs）是近年来发现的脑发育的重要调控因子。这些非编码的内源性小RNA分子在基因调控中具有重要功能，并且异常的miRNA成熟损害神经元分化，诱导细胞死亡，并破坏轴突生长。该提议的总体假设是，miRNA是POMC神经元正常发育所需的，并且在关键胎儿期期间特定miRNA的缺失导致POMC神经元的异常成熟和长期代谢失调。神经解剖学、神经生理学、生理学和分子学方法将通过解决以下具体目标来检验这一假设。具体目标1。我们将评估在POMC神经元的未成熟群体中miRNA成熟在细胞命运决定中的重要性。为此，我们将产生小鼠模型，其中Dicer（miRNA成熟的必需酶）在POMC神经元中缺失。我们假设表达Pomc的祖细胞可能在缺乏足够的miRNA成熟的情况下获得非POMC表型（例如NPY表型）。我们还将研究Dicer缺失对POMC和Pomc → NPY神经元连接的影响。具体目标2。我们将使用体内基因沉默方法来表征miR-103和miR-107的作用，特别是在胚胎发育过程中POMC神经元的及时成熟。我们还将探讨胚胎miR-103和miR-107在POMC神经元中的表达对POMC神经元活性和连接以及终生能量平衡调节和葡萄糖稳态的重要性。具体目标3。此外，我们将研究miR 103/107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。总之，这项工作将确定特定miRNA在参与终身能量平衡调节的神经系统发育中的关键作用。这些研究还可能为产前营养环境的改变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.