SP4 and schizophrenia: Consistent with the hypoglutamatergic hypothesis that schizophrenia is associated with impaired NMDA transmission, therefore, the Sp4 hypomorphic mouse presents a compelling animal model of the disorder in that it uniquely aggregates multiple validities: genetic (a risk gene), neurochemical (NMDAR hypofunction), behavioral (PPI deficits, etc.)and pharmacological (ketamine hypersensitivity).