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原因之一。由于我们已经在成人脑中发现了表达POMC的张力细胞，最近的证据表明，张力细胞具有干细胞样的特性，可以作为下丘脑神经元的前体细胞，我们假设张力细胞能够在下丘脑内侧基底区分化为POMC神经元，并有可能修复老化脑中衰竭的POMC神经元。为了开始验证这一假设，我们建议使用R21探索机制来确定张力细胞是否可以在出生后的大脑中产生POMC神经元，并整合到与摄食相关的回路中。为了进行这些研究，一个POMC缺失的转基因小鼠模型ArcPomcfneo/fneKO将与RaxCreERT2小鼠杂交，在该模型中，CRE重组酶仅在Tamoxifen反应的Tanycell中表达。因此，在由此产生的ArcPomcRaxRE小鼠的后代中观察到的所有POMC神经元只能来自伸展细胞。我们将确定在4个月的观察期内，当Tanycell POMC在出生后4天与出生后28天重新激活时，这些小鼠是否表现出代谢参数改善和肥胖的证据。分析中将包括生长、体重、食物摄入量、身体成分、能量平衡、葡萄糖平衡和甲状腺功能。在观察期结束时，动物将被安乐死，以确定与完整和空白POMC对照相比，激活的POMC神经元在下丘脑内侧基底的数量和位置，以及它们是否迁移到它们在下丘脑内侧基底的自然位置，并整合到与摄食相关的回路中。Tanycell来源的POMC神经元也将根据其神经递质的表达和对瘦素的反应性进行表型分析。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，并为调节黑素皮质素系统治疗肥胖和与衰老相关的代谢障碍提供新的、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.