Linking the molecular logic of sensory neuron diversity and somatosensory circuitry in mouse spinal cord: development of novel tools for viral tracing and 3D analysis

项目总结/摘要 脊髓背侧的感觉神经元（dIN）是中枢神经系统中第一个接受躯体感觉信号的部位 是控制姿势的感觉运动回路中的关键组成部分， 行为定义躯体感觉回路形成的发育原则和 提供特定感觉功能的神经元是我们理解感觉运动整合逻辑的关键 以及受伤或患病后的战略干预。所有的dIN都是由一小批分子定义的 胚胎细胞群，但标记物只是短暂表达，以及这些早期神经元如何多样化 并整合到成熟动物的感觉回路中， 未知迫切需要基因表达示踪剂和操纵个别类别的基因表达。 在胚胎期形成dIN，但在出生后建立电路。在这里，我们将 第一次产生小鼠，通过提供早期识别和成熟功能之间的差距， 在整个开发过程中，有选择地访问一个称为dI 1的dIN群体。我们将创建鼠标线 引入顺行和逆行病毒示踪剂以揭示和绘制脑中dI 1的突触靶点， 脊髓，并确定输入神经元dI 1 s，在DRG，脑和脊髓。这些线条会延伸到 选择性地将dI 1发育到出生后阶段的遗传途径，首先，通过依赖Cre的Cre方法， 允许依赖Cre的轴突和突触示踪剂进入，第二，表达蛋白质的小鼠 狂犬病病毒的跨突触追踪所需的。我们还将开发平台，以有效地分析 电路的解剖和连接。此外，我们将创建一个广泛需要的3D脊髓图谱， 神经元身份和映射电路的评估。为了了解调控dI 1的程序， 发展，我们还将确定和跟踪动态变化的转录签名在dI 1的整个 胚胎和出生后个体发育通过单细胞RNA测序。建议中所确立的工具 实验和分析将适用于所有dIN子集，并将提供资源和信息 的领域，并提供了一个模板的操纵和功能分析的躯体感觉通路在健康 和疾病。

Project Summary/Abstract Sensory neurons in the dorsal spinal cord (dINs) represent the first site in the CNS to receive somatosensory information from the periphery and are a crucial component in sensorimotor circuits that control posture and behavior. Defining the developmental principles of somatosensory circuit formation and the molecular identity of neurons that serve specific sensory functions is key to our understanding of the logic of sensorimotor integration and for strategic interventions following injury or disease. All dINs arise from a small array of molecularly defined embryonic cell populations, but markers are expressed only transiently and how these early neurons diversify and integrate into sensory circuits serving distinct sensory modalities in the mature animal remains largely unknown. There is an urgent need for genetic access to express tracers and to manipulate individual classes of developing dINs as they emerge during the embryonic period but establish circuits postnatally. Here, we will generate for the first time, mice that bridge the gap between early identity and mature function by providing access selectively to one population of dINs, called dI1s, throughout development. We will create mouse lines to introduce anterograde and retrograde viral tracers to reveal and map the synaptic targets of dI1s in brain and spinal cord, and to identify input neurons to dI1s, in DRG, brain and spinal cord. These lines will extend temporal genetic access selectively to developing dI1s into postnatal stages, by, first, a Cre-dependent Cre approach, permitting access by Cre-dependent axonal and synaptic tracers, and second, mice that express the proteins required for transsynaptic tracing using rabies virus. We will also develop platforms to analyze efficiently the anatomy and connectivity of the circuitry. Furthermore, we will create a widely needed 3D spinal cord atlas for assessment of neuronal identity and mapping circuitry. To understand the programs that regulate dI1 development, we will also identify and follow dynamic changes of transcriptional signatures in dI1s throughout embryonic and postnatal ontogeny by single cell RNA sequencing. The tools established in the proposed experiments and analyses will be applicable to all dIN subsets and will contribute both resources and information to the field, and provide a template for manipulation and functional analysis of somatosensory pathways in health and in disease.