Consistent with a role on spine morphology, we also identified genes involved in regulation of actin cytoskeleton such as Arhgef6 (Rac/Cdc42 guanine nucleotide exchange factor 6), Fgf11 (fibroblast growth factor 11), and Grlf1 (glucocorticoid receptor DNA binding factor 1) which could be responsible for elevated density of elongated spines in FXS patients (Irwin et al., 2001). The gene discussed is CDC42; the disease is fragile X syndrome.