So far, our CIRM funded project have provided strong evidence suggesting miRNAs as essential gene regulators in the self-renewal and pluripotency of embryonic stem cells, thus playing an important role in the generation of induced pluripotent stem cells (iPSCs). Several major progresses have been made for year 3. In short, we have carefully characterized the roles of miR-34 miRNAs in somatic reprogramming and indicated the importance of miR-34 inhibition in promoting stem cell self-renewal and somatic reprogramming. In addition, we completed two functional screens to identify miRNAs whose overexpression or inhibition regulates ES cell self-renewal and ES cell differentiation. Functional validation has been performed for majority of the hits from the screen. In particular, we have identified a miRNA, miR-meso, which specifically promotes mesoderm differentiation and represses ectoderm differentiation. Finally, using recombineering technology, we have constructed a BAC with Flag-tagged Lin28 at its endogenous locus. We have also constructed a piggy bac vector that allows us to generate stably integrated ES cell line that expresses Flag-tagged LIN28 for identification of novel LIN28 bound non-coding RNAs. These progresses significantly improved our understanding on the roles of non-coding RNAs in regulating stem cell self-renewal and pluripotency, and may lead to novel strategy for generating completely pluripotent human stem cells for clinical applications.
In 2011, a portion of our results funded by the CIRM project were published in Nature Cell Biology as a cover story, and we also filed a patent application reporting a novel strategy to increase somatic reprogramming efficiency.