FXS preclinical research on animals is limited to a few models, such as the Fmr1 knock-out (KO) mice, the Fmr1 KO zebrafish, and the Drosophila melanogaster model of FXS (Fmr1, FBgn0028734 [20]; herein named dFMR1) such as dFMR1B55 mutants [21,22,23]. The gene discussed is FMR1; the disease is fragile X syndrome.