Recently, Wu et al. have shown in mice that a dominant mutation in Crygc gene that causes cataracts could be rescued by Cas9 mediated DSB on the mutant allele which triggered homology-directed repair based on the endogenous WT allele, raising the hope for the application of current TALEN delivery technology to correct genetic diseases without the need for the introduction of exogenous DNA or RNA [23]. Here, CRYGC is linked to hereditary disease.