Only FMRP loss causes FXS, and only human FMRP can rescue Drosophila FXS model neurological defects (Coffee et al., 2010), including supernumerary synapse formation in the NMJ and brain (Pan et al., 2004; Dear et al., 2017), defective brain neural circuit remodeling (Tessier and Broadie, 2008; Doll et al., 2017), and impaired learning/memory (Bolduc et al., 2008; Jiang et al., 2016). This evidence concerns the gene FMR1 and fragile X syndrome.