Trans-Synaptic Tracing of Developing Somatosensory Circuits

 描述（由申请人提供）：概述在理解中枢躯体感觉回路的发育中的一个主要问题是缺乏可用的标记物，其允许观察在神经特性的初始指定和中枢连接的建立之间由单个类别的脊髓感觉神经元采取的路径和做出的选择。由于这个原因，背脊髓神经元的哪些胚胎亚群成为那些支持每种不同的体感功能的亚群仍然不清楚。虽然背角神经元的许多子集已划定在分化和早期迁移阶段的发展，有一个根本的需要，以弥合时期，当神经元可以根据其转录签名，当他们可以根据其功能电路进行识别。需要的方法，允许可视化的DRG神经元的功能类和个别类别的背角神经元之间的突触连接，并使我们能够确定在哪里以及如何这些背角神经元的项目集中在发展过程中，并在成人。最近证明，减毒狂犬病病毒可以定向到成熟神经系统中的特定细胞类型，并从外周的感觉神经元经突触进入目标中枢神经元，这为探索中枢躯体感觉系统的发育提供了一种方法，通过建立突触来定义功能连接，允许将功能分配给胚胎鉴定的神经元，并赋予一种标记技术，该标记技术允许可视化由单个类别的背角神经元形成的中枢通路。本R21研究的目的是开发方法，允许在发育过程中对发育中的体感回路进行选择性顺行和逆行跨突触追踪，并建立开发系统中通用的技术。

 DESCRIPTION (provided by applicant): Summary A major issue in understanding the development of central somatosensory circuitry is the lack of available markers that permit observation of the paths taken and choices made by individual classes of spinal sensory neurons between initial specification of neural identity, and the establishment of central connections. For this reason it also remains unclear which embryonic subsets of dorsal spinal neuron become those that subserve each distinct somatosensory function. Although many subsets of dorsal horn neuron have been delineated during differentiation and early migratory phases of development, there is a fundamental need to bridge the period when neurons can be identified according to their transcriptional signature and when they can be identified according to their functional circuitry. Methods are required that permit visualization of the synaptic connections between functional classes of DRG neurons and individual classes of dorsal horn neuron and allow us to determine where and how those dorsal horn neurons project centrally during development and in the adult. The recent demonstration that attenuated rabies virus can be directed to specific cell types in the mature nervous system and travel transsynaptically from sensory neurons in the periphery into target central neurons, provides a way to explore the development of the central somatosensory system, defining functional connections through the establishment of synapses, permitting the assignment of function to embryonically identified neurons and conferring a marking technique that allows visualization of the central paths forged y individual classes of dorsal horn neuron. The object of the research in this R21 is to develop methodology that will permit selective anterograde and retrograde transsynaptic tracing of developing somatosensory circuitry during development and to establish the techniques for general use in developing systems.