Frequency of ANKK1, DRD2, DRD3 gene polymorphisms in refractory schizophrenia patients

Schizophrenia is considered one of the most severe and complex mental disorders; it affects both the quality of life of the patient and his family. The dopamine hypothesis is the main concept concerning antipsychotic activity. Patients with treatment-refractory schizophrenia have a lower capacity for dopamine synthesis than those with a good response to first-generation antipsychotics. The polymorphisms rs1800497, rs1799732 and rs6280were chosen for evaluation because they are associated with decreased dopamine receptor expression and occur in genes encoding these receptors, namely, ANKK1, DRD2 and DRD3, respectively. This effect caused by these polymorphisms enhances refractoriness to treatment. We investigated the frequency of these polymorphisms and evaluated their association with refractory schizophrenia. This was a casecontrol molecular genetic study, with patients who were divided into three groups of 72 participants each: patients with refractory schizophrenia, with schizophrenia and controls with no diagnosis of any type of mental disorder. All participants of the research were from the extended Midwest region of Minas Gerais. Polymorphisms were evaluated by PCR followed by RFLP. The allele and genotype frequencies were determined, the association tests performed using Pearson's Chi Square, and Odds Ratio values were estimated. Genotypic models of dominance and heterosis were constructed. An association of the Del C allele of rs1799732 polymorphism and schizophrenia (P = 0.03) was found. Further research on this subject is merited, since response to treatment is of utmost importance to the patient's quality of life.