MicroRNA Cluster MiR-302-367 And MiR-106a-363 Promote The Generation Of IPS Cells And And Their Mechanisms

Induced pluripotent stem cells (iPS) and microRNA (miRNA), are two hot research topics in life sciences in the past few years. However, little is known on how miRNAs are regulated to control and participate in the reprogramming process. In this study, we examined the relationship between miRNAs and reprogramming in order to identify some miRNAs that could promote reprogramming and to understand their potential mechanism.We found that miR-106-363 and miR-302-367 cluster promoted reprogramming, and explored the mechanism of miR-302-367 cluster that accelerated mesenchymal-to-epithelial transition to promote reprogramming.In chapter 1, the general backgrounds on pluripotency, embryonic stem cells, iPS cells and miRNAs are reviewed. The core regulatory circuitry of pluripotency in embryonic stem cells, the latest progress in iPS cells, and the link between miRNAs and regulatory circuitry of pluripotency as well as reprogramming are described in detail.In chapter 2, our results on the relationship between miRNA clusters and reprogramming are presented. Over-expression of miRNA clusters miR-106-363 and miR-302-367 by retroviral vector yielded potent increase in the efficiency of reprogramming in mouse fibroblasts under diverse conditions. iPS cells established in this method were pluripotent using standard procedures including the formation of chimeric mice which were competent in germline transmission.In chapter 3, the mechanisms on how miRNAs promoted reprogramming were investigated. We found that reprogramming factors regulated the expression of some miRNAs in these clusters directly or indirectly. We identified that only miR-106a, 20b in miR-106a-363 and miR-302b, c, a, d in miR-302-367 were the active miRNAs for promoting reprogramming. Our data showed that miR-302-367 cluster promoted the formation of iPS colonied by targeting Tgfβ-receptor 2, promoting E-cadherin expression and accelerating mesenchymal-to-epithelial transition in reprogramming. Our work thus provided an interesting alternative to promote reprogramming using miRNAs and added new evidences to the emerging relationship between pluripotency and the epithelial phenotype.In chapter 4, we discussed the possibility that miRNAs can induce reprogramming directly.Next we will focus on the study of the regulation of non-coding RNAs including miRNA on cell fate, and the methods to reprogram more efficiently and safely using miRNAs.