FMR1 and fragile X syndrome: This was largely based on findings that multiple genes in syndromic forms of ASDs (e.g., Fragile X syndrome (FMR1), Rett syndrome (MECP2), Angelman syndrome (UBE3A), and genes that cause non-syndromic forms of ASDs (e.g., the Shank and neuroligin/neurexin family of proteins) have important roles during synapse development and refinement [2–8].