新的长链非编码RNA作为竞争性内源RNA参与小鼠胚胎干细胞多能性维持调控的机制研究

The transcriptional regulatory networks controlling ES cell self-renewal and pluripotency are the focus of intense interest, as study models for mammalian embryonic development and organogenesis with great therapeutic potential. Core transcriptional factors, such as OCT4, SOX2 and NANOG, maintain ES cell pluripotency by forming transcriptional regulatory circuitry. Long noncoding RNAs (lncRNAs) are newly discovered regulators of stem cell pluripotency maintenance. Our preliminary studies identified a new lncRNA, necessary for mouse ES cell pluripotency maintenance. Bioinformatic prediction showed that this lncRNA and Nanog contained common target sites of one miRNA, indicated this lncRNA may regulate pluripotency as a ceRNA by protecting NANOG from degradation in mouse ES cell. Besides confirming the ceRNA hypothesis, the project also aims to investigate the transcriptional regulation mechanism and developmental function of this lncRNA in mouse ES cell and embryonic development respectively. The findings will helpful for understanding lncRNA-mediated regulatory circuitry of pluripotency maintenance and provide new candidate genes for regulation of ES cell pluripotency.

研究干细胞多能性维持机制在阐明动物发育过程和再生医学应用等方面都具有重要意义。胚胎干细胞的多能性主要是由OCT4、SOX2和NANOG等关键转录因子形成的调控网络维持的。长链非编码RNA，即lncRNA，是新近发现的干细胞多能性调控因子。本项目的前期研究发现了一个小鼠胚胎干细胞特异表达的lncRNA，该lncRNA参与胚胎干细胞多能性的维持，抑制其表达导致细胞分化。生物信息分析发现该lncRNA与Nanog含有同一miRNA的预测靶位点，可能作为竞争性内源RNA调节Nanog的功能，进而影响胚胎干细胞多能性。本项目将验证上述预测结果的正确性，并深入研究该lncRNA的表达调控机制及其对体内胚胎发育的影响，从而解析该lncRNA参与胚胎干细胞多能性维持调控的分子机制和生理功能。项目的完成将有助于解析lncRNA在胚胎干细胞多能性调控网络中的作用，并为调控胚胎干细胞多能性提供新的候选基因。

胚胎干细胞具有自我更新和多向分化潜能，揭示干细胞多能性维持的精细调控机制对阐明动物发育机理、推动以干细胞治疗为核心的再生医学至关重要。干细胞多能性调控网络由核心转录因子OCT4、SOX2、NANOG及靶向调控核心转录因子的miRNA构成。最新研究发现，长链非编码RNA（lncRNA）参与干细胞多能性调控。某些lncRNA可以作为竞争性內源RNA，抑制miRNA与靶向基因的结合。本项目中，我们发现了miR-139-5p通过靶向结合Nanog 3'untranslated region (UTR)，抑制胚胎干细胞中Nanog的表达水平。而胚胎干细胞特异表达的新lncRNA，lnc-NAP，通过竞争性结合miR-139-5p维持Nanog的表达水平。核心转录因子OCT4和SOX2转录激活lnc-NAP的表达。敲低lnc-NAP引起Nanog表达水平下降，进而导致胚胎干细胞分化和小鼠胚胎致死。本研究发现了靶向调控核心转录因子NANOG的新非编码RNA，构建了非编码RNA参与干细胞多能性维持的精细调控网络。