SP4 and psychiatric disorder: Sp4 hypomorphic mice had reduced NMDAR1 expression throughout the brain [7,12] consistent with postmortem analysis of schizophrenic brains [13–15], and displayed a host of behavioral phenotypes endophenotypic of schizophrenia and other psychiatric disorders [7,10,11,16], including deficit in prepulse inhibition (PPI) [10] and, as we recently reported, hypersensitivity to ketamine [16].