A team of physicians specializing in genetics and neurology discovered that mental illnesses such as schizophrenia are closely linked to mutations in the GRIN2A gene. The GRIN2A gene regulates communication between neurons by producing the GluN2A protein. Of the 121 individuals studied, 85 had a GRIN2A variant and 23 of them developed a mental illness. The report also cites previous research that treated NMDA receptor deficiency, caused by the GRIN2A mutation, with L-serine, an amino acid. Schizophrenia Remains a Huge EnigmaSchizophrenia is a mental illness that manifests itself with delusions, hallucinations, disorganized thinking and language, behavioral changes, and loss of motivation or pleasure.