Different genome editing/targeting strategies have been applied to hemophilia mouse models, ranging from the insertion of an hFIX cDNA into the murine FIX locus (Wang et al., 2019) to the correction of mutations previously generated in the endogenous FIX locus (Guan et al., 2016; Huai et al., 2017; Ohmori et al., 2017). Here, F9 is linked to hemophilia.