S Staddon

Clinical applications of pharmacogenetics in psychiatry.

Abstract. Pharmacogenetic research has identified response-related mutant variants in metabolic enzymes and drug-targeted receptors. Allelic variants of dopaminergic and serotonergic receptors have been associated with clinical outcome and adverse events such as movement disorders. Deficient metabolic enzymes have been related to drug accumulation and toxic events. This information will help to design safer and more efficient drugs. However, the field is moving rapidly towards a new goal: the application of pharmacogenetics as a clinical tool for the prediction of treatment outcome. The first studies in this direction have proved the feasibility of using genetic information for the prediction of response to antipsychotic drugs and to treatment of Alzheimers disease. New strategies investigating genes related to specific symptoms and side-effects have produced encouraging results that can contribute to the improvement of the levels and accuracy of the predictions. This review tries to summarise recent advances and provides an overview of future clinical applications.

Association between dopamine D3 receptor gene polymorphisms and schizophrenia in an isolate population

There are several lines of evidence implicating the dopamine D3 receptor in the pathophysiology of schizophrenia. The Ser9Gly polymorphism of the dopamine D3 receptor gene (DRD3) has been the most extensively investigated DRD3 variant in connection with the disease but results have been inconclusive. Recent reports indicate that the Ser9Gly polymorphism is in linkage disequilibrium with other markers, but association studies between DRD3 haplotypes and schizophrenia have had mixed results. Genetic heterogeneity may be one of the causes of contradicting results. In order to clarify the role of DRD3 alterations in the aetiology of disease, we have investigated three D3 genetic variants (Ser9Gly, -205-G/A, -7685-G/C) in a sample of patients with schizophrenia or schizoaffective disorder (N=118) and controls (N=162) recruited from a human isolate from Navarra (Northern Spain) of Basque origin. Although no association was found between the Ser9Gly or the -205-A/G polymorphisms and disease, an excess of allele -7685-C was observed in patients (p=0.002 after correction for multiple analyses). Haplotype analysis shows the three markers to be in strong linkage disequilibrium (p<0.0001) and strongly associated with disease (p<1x 10(-5)). These results may suggest that these polymorphisms exert a combined or synergistic effect on susceptibility to schizophrenia, or are in linkage with an unknown causative factor. However, further replication in independent samples is required.