PTEN调控olig2启动内源性神经干细胞选择性向运动神经元分化及其对脊髓损伤的修复作用研究

The distinct differentiation of neural stem cells is the hotpoint of research in clinical neuroscience. Olig2 is the important factor regulated the NSCs located in ventral region of embryonic spinal cord differentiating into motor neurons. But the mechanism in upstream is not clear. The phosphatation of Ser147 played key roles on regulating olig2 function during the process of NSCs differentiation. PTEN is of the serine/threonine and tyrosine phosphatase characteristics. Our previous work indicated that there existed protein domains for interation between PTEN and olig2. Related research also indentified PTEN can regulate differentiation of NSCs through phosphating Akt. Howerver, the ser147 site on olig2 can be activated by phosphatation. So it is supposed that PTEN may take part in the process of NSC differentiation by regulating the phosphatation of Ser147 located on olig2. The mechanism of which may be related to the PI3K/Akt classical pathway and PTEN-olig2 direct interaction. Therefore, in this study, the effect of PTEN on distinct differentiating of NSCs was observed with gene transfection and interfering methods in vitro and in vivo,by which the interactions between PTEN and olig2 were investigated. Based on the above, the new molecular mechanism of NSCs selectively differentiating into motor neurons through affecting olig2 phosphorylation regulated by PTEN and the repairment effect on spinal cord injury were revealed. In finally, it may be provided new target for the treatment of spinal cord injury.

神经干细胞（NSC）定向分化是神经科学研究热点。olig2是调控胚胎脊髓腹侧NSC向运动神经元定向分化的重要分子，但其上游机制不清楚。Ser147位点磷酸化是调控olig2功能、决定NSC分化命运的关键。PTEN是一种丝/苏氨酸磷酸酶，我们前期研究提示：PTEN与olig2存在相互作用结构位点。研究还表明PTEN可改变Akt磷酸化而调控NSC分化,而olig2的Ser147位点可被磷酸化激活。故此推测：PTEN可能参与olig2Ser147磷酸化水平调节而调控NSC的定向分化。其机制可能与PTEN/Akt经典通路及PTEN-olig2直接作用有关。本研究以离体和在体NSC为研究对象，通过基因转染和干扰等技术，观察PTEN不同表达水平启动olig2对NSC定向分化调控及对脊髓损伤的修复作用；揭示PTEN调控olig2磷酸化对NSC向运动神经元选择性分化的新机制，也为脊髓损伤治疗提供新靶点。

脊髓损伤(SCI)所导致的机体运动及感觉功能障碍甚至死亡，不仅严重影响患者的生活质量，而且给家庭和社会带来巨大的精神和经济负担。在脊髓损伤后充分诱导内源性神经干细胞（NSC）的活化、增殖并向病灶迁移，定向分化为包括运动神经元在内的功能细胞以重建机体的运动功能就成为当前研究的难点和热点。本研究使用基因转染及干扰、神经病理、分子生物学以及神经行为学等技术，在体内、体外高及低表达PTEN基因，检测PTEN不同表达水平对离体培养NSC以及成年大鼠损伤脊髓内源性NSC向运动神元定向分化影响，并探讨与Olig2等相关转录因子的相互作用。结果表明:在离体培养的NSC中上调PTEN可抑制培养NSC的增殖，并通过促进转录因子Olig2的表达与激活而促进神经干细胞向运动神经元分化，而抑制PTEN表达后则促进NSC发生增殖，并诱导其向星形胶质细胞分化。阻断PTEN的下游通路后，并不能完全抑制其作用，提示PTEN可通过直接作用调控NSC分化。同时还揭示了 PTEN通过调控Olig2的表达，改变下游抑制性Hes1\Notch1和激活性转录因子Ngn2/Pax6的平衡而促进脊髓损伤后NSC向运动神经元分化、前角运动神经元的存活以及髓鞘的形成，并抑制脊髓损伤后星形胶质细胞的增生及分化，改变脊髓损伤后的微环境以及减少损伤后胶质瘢痕的形成从而促进大鼠脊髓损伤后下肢运动功能的恢复。该研究不仅为脊髓内源性NSC向运动神经元分化的机制研究提供有力的实验依据和理论指导，而且为临床治疗SCI提供一种新的思路和方法。