Applications of TALENs and CRISPR/Cas9 in human cells and their potentials for gene therapy

The newly developed TALENs and emerging CRISPR/Cas9 have spurred interests in the field of genome engineering because of their ease of customization and high-efficient site-specific cleavages. Although these novel technologies have been successfully used in many types of cells, it is of great importance to apply them in human-derived cells to further observe and evaluate their clinical potentials in gene therapy. Here, we review the working mechanism of TALEN and CRISPR/Cas9, their effectiveness and specificity in human cells, and current methods to enhance efficiency and reduce off-target effects. Besides, CCR5 gene was chosen as a target example to illustrate their clinical potentials. Finally, some questions are raised for future research and for researchers to consider when making a proper choice bases on different purposes.