Targeted genome engineering in human induced pluripotent stem cells by penetrating TALENs

Background:Zinc-finger nucleases(ZFNs)and transcription activator-like effector nucleases(TALENs)have been successfully used to knock out endogenous genes in stem cell research.However,the deficiencies of current gene-based delivery systems may hamper the clinical application of these nucleases.A new delivery method that can improve the utility of these nucleases is needed.Results:In this study,we utilized a cell-penetrating peptide-based system for ZFN and TALEN delivery.Functional TAT-ZFN and TAT-TALEN proteins were generated by fusing the cell-penetrating TAT peptide to ZFN and TALEN,respectively.However,TAT-ZFN was difficult to purify in quantities sufficient for analysis in cell culture.Purified TAT-TALEN was able to penetrate cells and disrupt the gene encoding endogenous human chemokine(C-C motif)receptor 5(CCR5,a co-receptor for HIV-1 entry into cells).Hypothermic treatment greatly enhanced the TAT-TALENmediated gene disruption efficiency.A 5%modification rate was observed in human induced pluripotent stem cells(hiPSCs)treated with TAT-TALEN as measured by the Surveyor assay.Conclusions:TAT-TALEN protein-mediated gene disruption was applicable in hiPSCs and represents a promising technique for gene knockout in stem cells.This new technique may advance the clinical application of TALEN technology.