GFAP and fragile X syndrome: Previous reports have been inconsistent about the effects of FXS on neuronal differentiation; one study [31], reported that in vitro differentiation of neurospheres derived from post-mortem human FXS brain and unaffected fetal brain showed differences in morphology, neurite number and length, and an altered ratio of Tuj1-positive to glial fibrillary acidic protein (GFAP)-positive cells; another similar study saw no significant differences in neural differentiation between FXS and control cells [32].