UCLA

The generation of induced pluripotent stem cells (iPSCs) by the forced overexpression of the Yamanaka factors--Klf4, Oct4, Sox2, and c-Myc--in terminally differentiated cells opened a new frontier in regenerative medicine. These iPSCs can provide a patient-specific source of cells that are able to differentiate into any cell type for possible therapeutic transplantation. However, the most common protocols for iPSC generation involve introduction of exogenous transgenes and genomic integration. Even with non-integrating protocols, iPSC quality and differentiation capacity varies on the reprogramming method used. It is now recognized that small activating RNAs (saRNAs) targeted to the promoter of certain genes can activate endogenous gene expression. Here we demonstrate the design and characterization of saRNAs that activate each of the endogenous Yamanaka genes, and a comprehensive analysis of KLF4 and MYC saRNA activity on global gene expression is presented. An optimized transfection protocol for reprogramming is developed, and we then investigate additional factors that enhance pluripotency gene expression when combined with saRNA. Knockdown of the histone methyltransferase SUV39H1 with siRNA is shown to dramatically increase saRNA activity on downstream gene activation. This approach was able to successfully generate iPSCs, but the results were not reproducible and the negative control cells also acquired pluripotency. We ultimately conclude that this method is unreliable at producing iPSCs at this stage until additional factors can be identified to improve saRNA activity for successful reprogramming.