The genetics of schizophrenia.

Schizophrenia is a complex biological disorder with multifactorial mode of transmission where non-genetic determinants are also play important role. It is now clear that it involves combined effect of many genes, each conferring a small increase in liability to the illness. Thus no causal disease genes or single gene of major effects, only susceptible genes are operating. Given this complexity, it comes as no surprise of the difficulty to find susceptible genes. However, schizophrenia genes have been found at last. Recent studies on molecular genetics of schizophrenia which focused on positional and functional candidate genes postulated to be associated with schizophrenia are beginning to produce findings of great interest. These include neuregulin (NRG-1, 8p12-21), dysbindin, (DTNBP1,6p22.3), G72 (13q34) / D-amino acid oxidase (DAAO,12q24), proline dehydrogenase (PRODH-2, 22q11.21), catechol-O-methyltransferase (COMT, 22q11.21), regulator of G protein signaling (RGS-4), 5HT2A and dopamine D3 receptor (DRD3). Applications of microarrays methods were able to locate positional candidate genes related to dopaminergic, serotonergic and glutamatergic neurotransmission. New genome scan project, seen in the light of previous scans, provide support for schizophrenia candidate region on chromosome 1q, 2q, 5q, 6p, 8p, 10p, 13q,15q and 22q. Other reports described including the application of LD mapping and positional cloning technique, microarray technology and efforts to develop quantitative phenotype. More exciting finding is expected in near future with the completion of Hap Map project.