In FXS, multiple animal models are available and commonly used, including Fmr1 knock-out (KO) mice [25], Dfxr (Drosophila fragile X-related gene) null drosophila [26], Fmr1 KO zebrafish [27], and Fmr1 KO rats [28]. Here, FMR1 is linked to fragile X syndrome.