Anatomical and Functional Analysis of POMC Neuronal Rescue by Tanycytes

 描述（由申请人提供）：POMC神经元的衰老被认为是年龄相关性肥胖的病因。由于我们已经确定了在成人大脑中表达POMC的伸长细胞，最近的证据表明，伸长细胞具有干细胞样的特性，可以作为下丘脑神经元的祖细胞，我们假设，伸长细胞能够分化成POMC神经元在下丘脑内侧基底，并有可能恢复衰老的大脑中失败的POMC神经元。为了开始测试这一假设，我们建议使用R21的探索机制，以确定是否伸长细胞可以产生POMC神经元在出生后的大脑和整合到喂养相关的电路。为了进行这些研究，将POMC无效转基因小鼠模型ArcPomcfneo/fneoKO与RaxCreERT 2小鼠杂交，所述小鼠模型由于下丘脑内侧基底部中POMC的丧失而具有肥胖表型，在所述RaxCreERT 2小鼠中Cre重组酶仅在伸长细胞中响应于他莫昔芬而表达。因此，在所得ArcPomcRaxRE小鼠的后代中观察到的所有POMC神经元只能来源于伸长细胞。我们将确定在4个月的观察期内，当伸展细胞POMC在出生后第4天与出生后第28天被重新激活时，这些小鼠是否显示出代谢参数和肥胖改善的证据。分析将包括生长、体重、摄食量、身体组成、能量平衡、葡萄糖稳态和甲状腺功能。在观察期结束时，将对动物实施安乐死，以确定与完整和无效POMC对照相比，活化的POMC神经元在内侧基底下丘脑中的数量和位置，以及它们是否迁移到内侧基底下丘脑中的天然位点并整合到进食相关回路中。还将针对其神经递质的表达和对瘦素的反应性对衍生于粗粒细胞的POMC神经元进行表型分析。这些研究有望扩大对下丘脑弓状核POMC系统神经生物学的理解，并为调节黑皮质素系统以治疗与衰老相关的肥胖和代谢紊乱提供新的见解。

 DESCRIPTION (provided by applicant): Senescence of POMC neurons is believed to contribute to the etiology of age-related obesity. As we have identified tanycytes to express POMC in the adult brain and recent evidence indicates that tanycytes have stem cell-like properties and can serve as progenitor cells for hypothalamic neurons, we hypothesize that tanycytes are capable of differentiating into POMC neurons in the mediobasal hypothalamus and potentially could restore failing POMC neurons in the aging brain. To begin to test this hypothesis, we propose to use the R21 exploratory mechanism to determine whether tanycytes can generate POMC neurons in the postnatal brain and integrate into the feeding-related circuitry. To perform these studies, a POMC null transgenic mouse model, ArcPomcfneo/fneoKO, which have an obese phenotype due to the loss of POMC in the mediobasal hypothalamus, will be crossed with RaxCreERT2 mice in which Cre-recombinase is expressed exclusively in tanycytes in response to tamoxifen. Therefore, all POMC neurons observed in the offspring of the resulting ArcPomcRaxRE mice can only be derived from tanycytes. We will determine whether these mice show evidence for improvement in metabolic parameters and obesity when tanycyte POMC is reactivated at postnatal day 4 vs. postnatal day 28 over a 4 month observation period. Included in the analysis will be growth, body weight, food intake, body composition, energy balance, glucose homeostasis and thyroid function. At the end of the observation period, animals will be euthanized to determine the number and location of activated POMC neurons in the mediobasal hypothalamus compared to intact and null POMC controls, and whether they migrate to their natural loci in the mediobasal hypothalamus and integrate into the feeding-related circuitry. Tanycyte-derived POMC neurons will also be phenotyped with respect to their expression of neurotransmitters and responsiveness to leptin. These studies are expected to expand the understanding of POMC system neurobiology in the hypothalamic arcuate nucleus and provide new and novel insights into ways the melanocortin system could be regulated to treat obesity and metabolic disorders associated with aging.