Understanding the role of tanycytes in the mammalian brain

提议：拟议的研究计划将探讨下丘脑伸长细胞的作用。* 背景和依据：伸展细胞是在一些缺乏完整血脑屏障（BBB）的有限下丘脑区域中发现的特化室管膜细胞。伸展细胞胞体形成BBB缺乏区域的心室底，其突起深入脑实质，接触有孔血管，从而暴露于外周循环。对伸长细胞的功能知之甚少;然而，考虑到它们的战略位置，在全身循环和中枢神经系统之间架起桥梁，这些细胞可能在循环和大脑之间传递信号方面发挥重要作用。* 我们最近的工作揭示了在终板血管器（OVLT）中存在大量的伸长细胞。OVLT是最重要的缺乏BBB的感觉区之一，为大脑提供来自外周的信息并有助于中枢介导的生理反应的产生。我们的数据表明，OVLT伸长细胞创建紧密嵌入局部神经元的密集网络。虽然在这个重要的大脑区域中，伸长细胞构成了一个普遍的群体，但它们的功能仍然难以捉摸。* 目标和方法：*1.研究OVLT伸长细胞在检测血液传播的循环信号中的作用，以改变神经元的活性。为了选择性地靶向伸长细胞，我们将用遗传（他莫昔芬诱导的波形蛋白-Cre小鼠系）和药理学工具操纵波形蛋白（伸长细胞的主要结构组分）的水平和活性，并且将通过使用腺相关病毒的条件性敲除和/或过表达来调节伸长细胞中的膜受体和转运蛋白的表达。这些方法将结合使用电生理学和钙成像在体外和体内的伸展细胞活性的功能分析。 *2。研究OVLT伸长细胞的结构组织。我们将使用超分辨率成像来表征伸长细胞的形态和组织，以及它们与神经元和血管系统的接触。3.研究OVLT伸长细胞的干细胞潜能。我们将使用不同谱系的标记物评估OVLT伸长细胞的干细胞潜能，使用他莫昔芬诱导的Nestin-Cre小鼠在体内进行长期伸长细胞谱系追踪，并通过检查OVLT伸长细胞的神经球生成潜能和使用电生理学评估新生神经元的功能来研究神经发生。* 结果：拟议的工作将探索以前未描述的细胞群在重要脑区的功能，该脑区作为外周循环和中枢神经系统之间的界面。破译伸长细胞在这一领域的作用将为哺乳动物大脑中最少探索的角落之一提供新的见解。

OBJECTIVES: The proposed research program will explore the role of hypothalamic tanycytes. ***BACKGROUND & RATIONALE: Tanycytes are specialized ependymal cells found in a few confined hypothalamic areas which lack a complete blood brain barrier (BBB). Tanycyte cell bodies form the ventricular floor in the BBB-lacking areas, and their processes extend deep into the brain parenchyma, contacting fenestrated vasculature, and thus are exposed to the peripheral circulation. The function of tanycytes is poorly understood; however, given their strategic location, bridging between the general circulation and the central nerve system, these cells might play an important role in transmitting signals between the circulation and the brain. ***Our recent work has revealed the presence of a large population of tanycytes in organum vasculosum of lamina terminalis (OVLT). OVLT is one of the most important BBB-lacking sensory areas providing the brain with the information from the periphery and contributing to the generation of centrally-mediated physiological responses. Our data show that OVLT tanycytes create a dense network tightly embedding local neurons. Although the tanycytes constitute a prevalent population in this vital brain region, their function remains elusive. ***AIMS & METHODS:***1. Studying the role of OVLT tanycytes in detecting blood-borne circulating signals to modify the activity of neurons. To selectively target tanycytes, we will manipulate the levels and activity of vimentin (a major structural component of tanycytes) with genetic (tamoxifen-inducible Vimentin-Cre mouse line) and pharmacological tools, and will modulate the expression of membrane receptors and transporters in tanycytes by conditional knockout and/or overexpression using adeno-associated virus. These approaches will be combined with functional analysis of tanycyte activity using electrophysiology and calcium imaging in vitro and in vivo. ***2. Investigating the structural organization of OVLT tanycytes. We will characterize tanycyte morphology and organization, and their contacts with neurons and vasculature using superresolution imaging.***3. Studying the stem cell potential of OVLT tanycytes. We will assess the stem cell potential of OVLT tanycytes using markers for different lineages, performing long-term tanycyte lineage tracing in vivo using tamoxifen-inducible Nestin-Cre mice, and studying the neurogenesis by examining neurospherogenic potential of OVLT tanycytes and evaluating the functionality of newborn neurons using electrophysiology. ***OUTCOME: The proposed work will explore the function of previously undescribed cell population in the vital brain area which serves as an interface between the peripheral circulation and the central nervous system. Deciphering the role of tanycytes in this area will provide new insights into one of the least-explored corners of the mammalian brain.