miRNA的家族性与成簇性的基因组特征显示它们会形成复杂的功能叠加性与协同性组合，精密调控各种生物学进程。这些调控组合或可对由某种因素引起的表型变化进行及时补偿，导致敲除单个或几个miRNA的遗传学试验不会出现显著的生物学表型。我们将该调控模式引起的表型变化特点称为miRNA的“表型弹性”。我们以胚胎干细胞早期定向中胚层分化为模型，通过CRISPR/cas9介导的基因敲除方法系统鉴定这些在中胚层分化中占主导地位和/或不同阶段特异表达的miRNA基因簇，阐明它们在特定链系分化中的关键作用，并探讨miRNA簇各成员之间的“表型弹性”关系，解析“表型弹性”发生的分子机制。这些研究将有助于我们重新认识miRNA的生物学功能，深入理解miRNA成簇的生物学意义，同时有助于揭示胚胎干细胞分化的调控网络，更好地指导胚胎干细胞的体外定向分化。

Genomic properties and mechanistic function of microRNA (miRNA) indicate that they comprehensively regulate multiple biological processes by many additive and synergistic groups. These regulatory groups might compensate the phenotypic changes caused by specific factors in time, resulting in the reality that people couldn’t observe significant phenotypes after a single miRNA or several miRNAs knockdown. We define this phenotypic character induced by the complex regulatory pattern as “Phenotypic Fexibility” of miRNA. With the model of directed differentiation of embryonic stem cells (ESCs) into mesoderm cells, we will systematically identify the dominant miRNA clusters during the differentiation process or differentially expressed miRNA clusters at different developmental stages via CRISPR/cas9-mediated deletion, to elucidate their essential function in specific differentiation, investigate the relation of phenotypic fexibility among.different members of the miRNA clusters and analyze the molecular mechanism behind the synergistic regulation. All of the studies will contribute to re-recognize the biological function of miRNAs, understand the evolutional significance of miRNA clusters, uncover the regulatory network of differentiation of ESCs and guide the committed differentiation of ESCs in vitro.