FMR1 and fragile X syndrome: It is interesting to note that longer dendritic spines found in the cortex of CGG KI mice have also been reported in Golgi studies of postmortem tissue in FXS [54,55] and in Fmr1 KO mice [56,57], whereas the reduction in dendritic branching complexity in CGG KI mice was not found in the Fmr1 KO mouse [56].