Fmr1-KO mice exhibit defects in cognition and learning/memory formation (Huber et al. 2002; Arbab et al. 2018; Boone et al. 2018; Talbot et al. 2018), dendritic spine morphology and dynamics (Comery et al. 1997), and synaptic plasticity (Lauterborn et al. 2007; Lee et al. 2011; Muddashetty et al. 2007), closely paralleling phenotypes observed in human FXS (Kazdoba et al. 2014). The gene discussed is FMR1; the disease is fragile X syndrome.