Oct4与Xist在Ascl1介导的原始态多能干细胞正向编程中的调控机制研究

Xist是X染色体失活的主要调控因子，其通过招募特异蛋白调节转录抑制，介导X染色体沉默，从而实现剂量补偿效应。Xist在早期胚胎正常发育、细胞命运决定和疾病发生中扮演着重要角色。然而目前对Xist参与发育分化的表观调控机制及其影响细胞命运转变的功能知之甚少。前期结果显示：1）Xist在原始态多能干细胞启动正向编程时出现瞬时高表达，且高于雌性体细胞中维持X染色体失活所需的水平；2）Xist异常表达受Oct4调控，且Oct4结合到Xist及其拮抗基因Tsix及Tsx的基因组上。由此推测，Oct4与Xist交互作用，调控表观遗传标志，从而改变细胞命运。本项目拟以Ascl1介导的原始态多能干细胞正向编程为模型，研究正向编程的转录动态过程，Oct4对Xist异常表达的调控机制，Xist调控表观遗传在细胞命运转变中的生物学功能，进而为疾病的发生机制和再生医学的临床应用提供新的见解。

Xist is the master regulator of X chromosome inactivation. Xist establishes dosage compensation by mediating X chromosome inactivation via recruiting specific protein complexes and triggering gene silencing. It plays a vital role in early embryonic development, cell fate determination and disease pathology. However, how Xist regulate epigenetics and influence cell fate transition remains unclear. Interestingly, our preliminary data shows that 1) Xist is highly expressed in forward programming from male naïve pluripotent stem cells (nPSCs) and its expression level is higher than that required in female somatic cells; 2) Xist is rescued by Oct4 and Oct4 binds the locus of X-chromosome-inactivation related genes Xist and its antisense RNA Tsix. Therefore, we hypothesize that Oct4 crosstalk with Xist and change cell fate by mediating epigenetic state. In this project, we will validate this hypothesis in details by investigating the dynamics of transcriptome during forward programming of nPSCs by inducing Ascl1 and the function and involved mechanism of Oct4 and Xist during these process. Resolving these questions will elucidate how developmental processes are regulated, enhance the quality of induced cell types by TF-induced cell fate change, and offer a new perspective to clinical application of regenerative medicine.