脊髓兴奋性中间神经元功能多样化的分子调控机制

Spinal locomotion (swimming, walking, etc.) is generated by the local spinal neural circuit, named spinal central pattern generator (CPG). Descending inputs originating from the supraspinal command centers in the brain activate and drive the spinal CPG. The activation of spinal CPG produces two consequences: one is to generate the the rhythmic and left-right patterned locomotion; the other is to activate the spinal efference copy, which in turn acts to influence the brain command centers retrogradely...During the development, the interaction of two morphogen gradients, Shh and BMPs, results in five classes of neurons (V0, V1, V2, V3 interneurons and motor neurons） in the ventral half of the neural tube. Among V2 interneurons, all V2a interneurons, the ipsilateral excitatory interneurons, express the transcription factor Chx10. However, our preliminary results show that even though V2a interneurons expressing the same protein, they displayed different intrinsic properties and played different roles in the spinal locomotion. These results suggest that further molecular mechanisms are established in the neural network to control the functional diversities of V2a interneurons...In this application, we will take advantage of adult zebrafish preparation and achieve two goals. First, we will combine the electrophysiology and single neuron RNA-seq to explore the mechanisms controlling the functional diversities of V2a interneurons; Second, we will use two-photon calcium image, two-photon guided patch clamp as well as the optogenetic tools to further study the function of V2a interneurons in the spinal efference.

位于脊髓腹侧的运动神经网络被命名为“脊髓中央运动模式产生器”（Spinal Central Pattern Generator，CPG）”。同侧投射的兴奋性谷氨酸能中间神经元在此神经网络中的地位非常重要，肩负着设定整个神经网络的兴奋性和节律性的功能。根据目前的脊髓神经元的分类方式，在脊椎动物的脊髓中同侧兴奋性的中间神经元被称之为V2a中间神经元，表达转录因子蛋白Chx10。然而在前期预实验中我们发现发现，表达同一种转录因子蛋白的V2a中间神经元的功能是多样化的，并且功能的多样化与神经元的形态特征相匹配。在本申请中，我们一方面通过对脊髓V2a神经元进行电生理记录结合单细胞RNA-seq的方法来寻找决定V2a兴奋性神经元功能多样化的分子机制，另一方面通过双光子钙离子成像，双光子介导的在体膜片钳记录和光遗传学等方式对V2a神经元在脊髓运动中的功能做更细致的研究。

位于脊髓腹侧的运动神经网络被命名为“脊髓中央运动模式产生器”（Spinal Central Pattern Generator，CPG）”。同侧投射的同侧兴奋性的V2a中间神经元在此神经网络中的地位非常重要，肩负着设定整个神经网络的兴奋性和节律性的功能，表达转录因子蛋白Chx10。在国家自然科学基金面上项目（31771168）的支持下，本研究取得了以下三点成绩：1. 该项研究成果首次从脊髓神经元的功能多样化角度解释了编码脊髓运动速度的神经环路基础，为研究脊髓神经元亚分类、神经环路构成以及相关疾病打下基础（Nature Communications, 2018）；2. 发现与躲避相关的脊髓V2a神经元的电生理、分子和形态特征，解析出其逃避神经环路的构成和突触联接的细节，从而阐明一种行为抉择的脊髓内机制 （PNAS， 2021）；3. 证明损伤后以V2a神经元为代表的脊髓兴奋性中间神经元高表达五羟色胺1b受体，新生五羟色胺能神经元亚型聚集在损伤处通过其高度且持续活跃的电活动特征，为损伤处脊髓节段提供高浓度的五羟色胺微环境，促进受损的脊髓神经环路修复和运动功能的恢复 （Nature Communications, 2021）。