Directed differentiation of human induced pluripotent stem cells (iPSCs) into 
retinal pigmented epithelium (RPE) holds great promise in cell replacement 
therapy for patients suffering from degenerative eye diseases, including 
age-related macular degeneration (AMD). In this study, we generated iPSCs from 
human dermal fibroblasts (HDFs) by electroporation with episomal plasmid vectors 
encoding OCT4, SOX2, KLF4, L-MYC together with p53 suppression. Intriguingly, 
cell reprogramming resulted in a metastable transcriptional activation and 
selective demethylation of neural and retinal specification-associated genes, 
such as OTX2, RX1 and SIX3. In contrast, RPE progenitor genes were 
transcriptionally silent in HDFs and descendant iPSCs. Overexpression of OCT4 
and SOX2 directly stimulated the expression of OTX2, RX1 and SIX3 in HDFs and 
iPSCs. Luciferase and chromatin immunoprecipitation (ChIP) assays further 
identified an OCT4- and two SOX2-binding sites located in the proximal promoter 
of OTX2. Histone acetylation and methylation on the local promoter also 
participated in the reactivation of OTX2. The transcriptional conversion of RX1 
and SIX3 genes partially attributed to DNA demethylation. Subsequently, iPSCs 
were induced into the RPE cells displaying the characteristics of polygonal 
shapes and pigments, and expressing typical RPE cell markers. Taken together, 
our results establish readily efficient and safe protocols to produce iPSCs and 
iPSC-derived RPE cells, and underline that the reactivation of anterior neural 
transcription factor OTX2, eye field transcription factor RX1 and SIX3 in iPSCs 
is a feature of pluripotency acquisition and predetermines the potential of RPE 
differentiation.