Our main finding was of an autosomal dominant heterozygous frameshift mutation in the GRIN3B gene encoding the GluN3B subunit of the NMDA receptor that was present in all of the affected family members of our pedigree analysis and in 63·6% of all patients with schizophrenia in our ReelinSys study population. The gene discussed is GRIN3B; the disease is schizophrenia.