Candidate gene polymorphisms among North Indians and their association with schizophrenia in a case-control study.

Knowledge of candidate gene polymorphisms in a population is useful for a variety of gene-disease association studies, particularly for some complex traits. A number of candidate genes, a majority of them from the monoaminergic pathway in the brain, have been very popular in association studies with schizophrenia, a neuropsychiatric disorder. In this study diallelic/multiallelic polymorphisms in some dopaminergic, serotonergic and membrane-phospholipid-related genes have been evaluated in a control population recruited from North India. Association, if any, of these allelic variants with schizophrenia has been tested using a case-control approach. The case data have been taken from our published family-based association studies in schizophrenia. Of the eight genes tested in this study, association with schizophrenia was observed for only two gene polymorphisms, one in the promoter region of the serotonin 2A receptor gene and the other in the tryptophan hydroxylase gene. One new allele for the dopamine transporter gene (with eight repeats, 570-bp size), not reported in any population so far, has been identified in one individual in our sample. The data generated in this study, besides providing a normative background for various disease association studies, are a significant contribution to the population-specific genome database, a currently growing requirement.

Molecular genetics of schizophrenia: past, present and future.

Schizophrenia is a severe neuropsychiatric disorder with a polygenic mode of inheritance which is also governed by non-genetic factors. Candidate genes identified on the basis of biochemical and pharmacological evidence are being tested for linkage and association studies. Neurotransmitters, especially dopamine and serotonin have been widely implicated in its etiology. Genome scan of all human chromosomes with closely spaced polymorphic markers is being used for linkage studies. The completion and availability of the first draft of Human Genome Sequence has provided a treasure-trove that can be utilized to gain insight into the so far inaccessible regions of the human genome. Significant technological advances for identification of single nucleo-tide polymorphisms (SNPs) and use of microarrays have further strengthened research methodologies for genetic analysis of complex traits. In this review, we summarize the evolution of schizophrenia genetics from the past to the present, current trends and future direction of research.