The CRISPR/Cas9-mediated correction has been successfully applied to the CFTR mutation for the treatment of patients with CF (Durand et al., 2012; Liu et al., 2012; Schwank et al., 2013; Martin, 2015; Mou et al., 2015; Dedhia et al., 2016). The gene discussed is CFTR; the disease is cystic fibrosis.