金颖研究组揭示microRNA调控细胞凋亡方面的新作用

　　

近日，国际生物医学重要学术期刊《细胞死亡及疾病》（Cell Death and Disease）上发表了中科院上海生命科学研究院/上海交通大学医学院健康科学研究所，中国科学院干细胞生物学重点实验室金颖研究组题为“MicroRNA-195 targets ADP-ribosylation factor-like protein 2 to induce apoptosis in human embryonic stem cell-derived neural progenitor cells”的最新研究进展。

近年来，如何利用人胚胎干细胞这一独特的资源解决发育和再生医学上的重要问题已经成为研究热点之一。金颖研究员领导的干细胞研究组已经成功地建立了多株具有无限自我更新能力和分化全能性的人胚胎干细胞系。

在此项研究中，博士研究生周阳在金颖研究员的指导下，首先将人胚胎干细胞定向诱导分化成为神经前体细胞，将这一分化模型作为基础研究转化的桥梁。进一步，他们通过一系列实验证明了microRNA-195（miR-195）能够通过抑制下游GTP结合蛋白ARL2调控神经前体细胞的生存和凋亡。实验结果表明ARL2作为miR-195的功能下游基因，对于维持神经前体细胞生存是必需的。

同时，他们还发现了miR-195在神经毒素鱼藤酮和百草枯处理神经前体细胞后表达量上升，揭示miR-195参与了神经毒素诱导的细胞凋亡过程。由于神经毒素鱼藤酮和百草枯可能是诱发帕金森氏症的环境因素，因此本研究为研究神经毒素引起的神经退行性疾病的发病机制和治疗提供了新的思路。

该研究主要克服了人胚胎神经前体细胞较难获得的困难，成功利用了人胚胎干细胞定向往神经细胞分化的体外模型，对人类早期神经发育过程中神经前体细胞的细胞行为及其分子机制进行了深入的研究和探索，为许多重要科学问题，如研究各种环境毒素或者是复合体药物对胎儿早期神经发育影响，各种神经退行性疾病的发病机制等的研究打开了方便之门，并被推荐到F1000Prime（F1000Prime Recommendations, Dissents and Comments for [Zhou Y et al., Cell Death Dis 2013, 4:e695]. In F1000Prime, 16 Jul 2013; F1000Prime.com/718023613）。

此项课题研究得到了健康所沈南研究员课题组的协助，并且获得国家科技部、国家自然科学基金委，国家高技术研究与发展计划及中国科学院先导项目的经费资助。

原文摘要：

MicroRNA-195 targets ADP-ribosylation factor-like protein 2 to induce apoptosis in human embryonic stem cell-derived neural progenitor cells

Neural progenitor cells (NPCs) derived from human embryonic stem cells (hESCs) have great potential in cell therapy, drug screening and toxicity testing of neural degenerative diseases. However, the molecular regulation of their proliferation and apoptosis, which needs to be revealed before clinical application, is largely unknown. MicroRNA miR-195 is known to be expressed in the brain and is involved in a variety of proapoptosis or antiapoptosis processes in cancer cells. Here, we defined the proapoptotic role of miR-195 in NPCs derived from two independent hESC lines (human embryonic stem cell-derived neural progenitor cells, hESC-NPCs). Overexpression of miR-195 in hESC-NPCs induced extensive apoptotic cell death. Consistently, global transcriptional microarray analyses indicated that miR-195 primarily regulated genes associated with apoptosis in hESC-NPCs. Mechanistically, a small GTP-binding protein ADP-ribosylation factor-like protein 2 (ARL2) was identified as a direct target of miR-195. Silencing ARL2 in hESC-NPCs provoked an apoptotic phenotype resembling that of miR-195 overexpression, revealing for the first time an essential role of ARL2 for the survival of human NPCs. Moreover, forced expression of ALR2 could abolish the cell number reduction caused by miR-195 overexpression. Interestingly, we found that paraquat, a neurotoxin, not only induced apoptosis but also increased miR-195 and reduced ARL2 expression in hESC-NPCs, indicating the possible involvement of miR-195 and ARL2 in neurotoxin-induced NPC apoptosis. Notably, inhibition of miR-195 family members could block neurotoxin-induced NPC apoptosis. Collectively, miR-195 regulates cell apoptosis in a context-dependent manner through directly targeting ARL2. The finding of the critical role of ARL2 for the survival of human NPCs and association of miR-195 and ARL2 with neurotoxin-induced apoptosis have important implications for understanding molecular mechanisms that control NPC survival and would facilitate our manipulation of the neurological pathogenesis.