脊髓五羟色胺能神经元在脊髓损伤后运动神经环路重建中的作用

脊髓损伤是一种重大的创伤性疾病。脑源性5-HT通过相应受体影响“脊髓中央运动模式产生器（CPG）”生理活动。脊髓损伤后，大脑下行投射的5-HT神经元轴突中断，在脊髓内的再生受限，进而阻碍脊髓运动恢复。预实验数据显示，成年斑马鱼脊髓内源性5-HT神经元始终在损伤周围富集，并且其数量与神经元轴突再生及运动恢复呈线性相关。因此，我们假设这些脊髓内源5-HT神经元能补偿损伤后5-HT供应缺失，并通过作用于关键受体基因，促进损伤后的神经元轴突再生和运动神经环路重建。探索激活脊髓内源性5-HT神经元的再生或分化机制，以及筛选有效的5-HT受体靶点对促进损伤后脊髓运动恢复意义重大。本申请中，我们利用RNA-Seq结合CRISPR/Cas9基因敲除，一方面探索损伤后5-HT神经元来源及富集机制；另一方面寻找人源同系5-HT受体靶点，研究5-HT神经元促进损伤后神经元轴突再生和运动神经环路重建的分子机制。

Spinal cord injury (SCI) is a major traumatic disease. Brainstem-derived 5-HT has been recognized as a potent modulator of spinal central pattern generator (CPG) physiological function. Spinal cord injury may cause complete severing of the supraspinal serotonergic projections. Also, the regeneration of the descending fibers is limited. Loss of 5-HT is one of the major limiting factors that prevents the recovery of spinal motor function. Our preliminary results in adult zebrafish reveal a dynamic change of intraspinal 5-HT neuron numbers after spinal cord transection, and these neurons always distribute around the injury site. The number of which shows linear correlation with axon regrowth and locomotion recovery. Therefore, we hypothesize that these intraspinal 5-HT neurons may compensate for the 5-HT deficiency after spinal cord injury, and facilitate axon regrowth and locomotor circuit reconstruction by binding specific receptors. It may be of great significance to facilitate either regeneration or differentiation of these intraspinal 5-HT neurons to improve locomotion recovery. In this application, we will combine RNA-seq and CRISPR/Cas9 based gene knockout to explore the mechanisms inducing 5-HT accumulation around injury site. And find the downstream human homologous 5-HT receptors, through which 5-HT neurons promote axon regeneration and reconstruction of locomotor circuit.