FZD6 and major depressive disorder: In this study, to better determine the functional role of rs61753730 in depression, we generated an Fzd6-KI mouse model with rs61753730 mutation by applying the cutting-edge CRISPR/Cas9 technique, which can target even a single nucleotide (Heidenreich and Zhang, 2016; Pickar-Oliver and Gersbach, 2019; Wu et al., 2019, 2020).