少突胶质细胞的内在兴奋性在髓鞘发育和损伤修复中的作用及机制

Oligodendrocytes (OLs) form myelin in the central nervous system. An important symptom in numerous neuronal or mental diseases, such as multiple sclerosis, white matter injury, autism and schizophrenia is myelin defects. The differentiation of oligodendrocytes from oligodendrocyte precursor cells (OPCs) and their timely differentiation into myelinated OLs play critical roles in myelination and are regulated by multiple cell-intrinsic and extracellular factors. However, the mechanisms underlying the OPC differentiation and myelin development are fully understood. The role of the excitability of oligodendrocyte in myelination was barely reported. Using the IVMR knock-in mice, we can specifically inhibit the cell excitability in oligodendrocyte linage cells. In this mice strain we found that the myelin can not be maintained in the adult. In this project, we will continue to utilize molecular biological, biochemical, cellular biological and Cre-Loxp-based knock-in approaches to study the myelination defect and the myelin maintaining in the conditioned knock-in mice and their underlying mechanisms. We will also investigate the excitability of oligodendrocyte in the myelin injury and remyelination using cuprizone-induced demyelination model. Our results will reveal the mechanisms of roles of oligodendrocyte excitability in myelination, myelin maintaining and remyelination in CNS and supply new therapeutic target and reliable animal models for myelin-related diseases and screening of new drugs.

中枢神经系统髓鞘由少突胶质细胞形成。髓鞘缺陷常见于多发性硬化症、白质损伤、精神分裂症等疾病。少突胶质细胞由少突胶质细胞前体细胞（OPC）分化并发育成熟产生。研究髓鞘发育和OPC细胞分化调控的机制对髓鞘相关疾病以及髓鞘损伤修复治疗具有重要意义。目前对髓鞘发育和OPC分化的调控机制了解仍不完全。利用条件性IVMR敲入小鼠，我们可以在少突胶质细胞系中特异抑制其兴奋性，并发现在兴奋性受抑制时，成年小鼠髓鞘不能维持。本项目将在前期研究基础上，综合利用分子，生化和细胞生物学等实验技术来研究由IVMR调节的少突胶质细胞兴奋性在中枢神经系统髓鞘发育，维持中的作用及其可能的分子机制，并利用小鼠脱髓鞘模型来研究兴奋性在髓鞘损伤修复中的作用。该项目将能揭示少突胶质细胞自身兴奋性对中枢神经系统髓鞘发育，维持及髓鞘损伤修复的调控及其分子机制，为髓鞘相关疾病及新药的筛选鉴定提供潜在的新治疗靶点和可靠的动物及细胞模型。

中枢神经系统髓鞘由少突胶质细胞（OLs）形成。髓鞘缺陷常见于多发性硬化症、白质损伤、精神分裂症等疾病。少突胶质细胞由少突胶质细胞前体细胞（OPC）分化并发育成熟产生。研究髓鞘发育和OPC细胞分化调控的机制对髓鞘相关疾病以及髓鞘损伤修复治疗具有重要意义。目前对髓鞘发育和OPC分化的调控机制了解仍不完全。研究发现少突胶质细胞可以被兴奋，但是其兴奋性对髓鞘化是否有影响还未见报道。在本项目中，利用条件性IVMR敲入小鼠，我们可以在少突胶质细胞系中特异抑制其兴奋性，来研究其在髓鞘发育，维持以及损伤修复中的可能作用与机制。我们发现在新生小鼠中抑制少突胶质细胞兴奋性，髓鞘发育受阻；而在成年小鼠中抑制少突胶质细胞兴奋性则导致髓鞘不能维持。而在Cuprizone诱导的脱髓鞘模型中，抑制少突胶质细胞兴奋性将加速脱髓鞘进程，并且减慢髓鞘的恢复。除了检测到兴奋性影响髓鞘关键转录因子（Olig1与Olig2）表达外，通过基因组测序，我们筛选出三个参与兴奋性调节髓鞘化的关键因子：Gab1、LGI1与Epac。其中Gab1受PDGF的信号严格调控，可能是OPC分化的启动开关；Gab1还能通过与GSK3β的结合调节GSK3β的活性，控制β-Catenin的细胞核内含量，从而调节髓鞘基因转录进而控制髓鞘发育。LGI则通过促进OPC分化来调节髓鞘发育与损伤修复；同时LGI1还能调节TSC1-mTORC1信号通路的平衡，从而控制少突胶质细胞中的脂肪酸合成进而影响髓鞘化。最后Epac则通过抑制OPC增殖，对髓鞘发育进行时间调控。该项目揭示了少突胶质细胞自身兴奋性对中枢神经系统髓鞘发育，维持及髓鞘损伤修复的调控及其分子机制，为髓鞘相关疾病及新药的筛选鉴定提供潜在的新治疗靶点和可靠的动物及细胞模型。