FMR1 and autism: Loss of FMRP, as observed in fragile X syndrome (FXS), is a leading monogenic cause of autism and intellectual disability, and is characterized by altered structural and functional synaptic plasticity throughout the brain (Irwin et al., 2001; Nimchinsky et al., 2001; Huber et al., 2002; Antar et al., 2006; Grossman et al., 2006; Pfeiffer et al., 2010; Bagni et al., 2012; Smith et al., 2014; Neuhofer et al., 2015).