Generation of cell-type-specific gene mutations by expressing the sgRNA of the CRISPR system from the RNA polymerase II promoters

Recently, the CRISPR/Cas9 system is emerging as a powerful tool for genome editing （Chang et al., 2013; Li et al., 2013; Niu et al., 2014; Shen et al., 2013; Wan et al., 2015; Wang et al., 2013） and genetic screening （Konermann et al., 2015）, and holds great promise for biomedical applications in disease modeling and gene therapy by in vivo genome editing （Mad- dalo et al., 2014; Xue et al., 2014）.