In this study, we demonstrate the prevention and reversal of motor coordination and cognitive deficits (as observed by the rotarod test and the elevated plus maze test) in anti-SEMA4D-treated Mecp2T158A/y mice, whereas Mecp2T158A/y mice treated with control antibody exhibited deficits as early as 6 weeks of age which progressively worsened throughout the trial. The gene discussed is SEMA4D; the disease is Cognitive impairment.