Reprogramming to pluripotency using designer TALE transcription factors targeting enhancers

The modular DNA recognition code of the transcription-activator-like effectors (TALEs) from plant pathogenic bacterial genus Xanthomonas provides a powerful genetic tool to create designer transcription factors (dTFs) targeting specific DNA sequences for manipulating gene expression. Previous studies have suggested critical roles of enhancers in gene regulation and reprogramming. Here, we report dTF activator targeting the distal enhancer of the Pou5f1 (Oct4) locus induces epigenetic changes, reactivates its expression, and substitutes exogenous OCT4 in reprogramming mouse embryonic fibroblast cells (MEFs) to induced pluripotent stem cells (iPSCs). Similarly, dTF activator targeting a Nanog enhancer activates Nanog expression and reprograms epiblast stem cells (EpiSCs) to iPSCs. Conversely, dTF repressors targeting the same genetic elements inhibit expression of these loci, and effectively block reprogramming. This study indicates that dTFs targeting specific enhancers can be used to study other biological processes such as transdifferentiation or directed differentiation of stem cells.