Rat models of FXS include the FMR1-knockout (FMR1-KO) mice, which show cognitive deficits, abnormal immature neuronal morphology, and lack the normal fragile X mental retardation protein (FMRP), that is important for normal cognitive development (Restivo et al., 2005; Oddi et al., 2015). Here, FMR1 is linked to fragile X syndrome.