Population stratification in European South-American subjects and its importance to psychiatric genetics research in Brazil

2012

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Schizophrenia is a severe psychiatric disorder characterized by psychotic symptoms and functional impairment, with recurrent relapses and continuing disability. The risk factors for schizophrenia are indicators currently perceived as epiphenomena of pathophysiological processes resulting from geneenvironment interactions that remain poorly understood 1 . Widespread impairments in brain function and structure have been shown in schizophrenia cases. It is also clear that, to a lesser degree, unaffected family members share many of the neurobiological abnormalities found in affected individuals, which suggests that the alleles that underlie the genetic risk of schizophrenia may primarily exert their effects on intermediate traits such as cerebral structure or function ABSTRACTSchizophrenia is a severe psychiatric disorder with frequent recurrent psychotic relapses and progressive functional impairment. It results from a poorly understood gene-environment interaction. The gene encoding catechol-O-methyltransferase (COMT) is a likely candidate for schizophrenia. Its rs165599 (A/G) polymorphism has been shown to be associated with alteration of COMT gene expression. Therefore, the present study aimed to investigate a possible association between schizophrenia and this polymorphism. The distribution of the alleles and genotypes of this polymorphism was investigated in a Brazilian sample of 245 patients and 834 controls. The genotypic frequencies were in Hardy-Weinberg equilibrium and no statistically significant differences were found between cases and controls when analyzed according to gender or schizophrenia subtypes. There was also no difference in homozygosis between cases and controls. Thus, in the sample studied, there was no evidence of any association between schizophrenia and rs165599 (A/G) polymorphism in the non-coding region 3' of the COMT gene.Key words: enzyme, genetics, psychosis, schizophrenia. RESUMOA esquizofrenia é um grave transtorno psiquiátrico que apresenta freqüentes recorrências psicóticas e incapacitação progressiva. Resulta de uma interação gene-ambiente ainda pouco compreendida. O gene da catecol-O-metiltransferase (COMT) é considerado um possível candidato para esquizofrenia. O polimorfismo genético rs165599 (A/G) da COMT foi associado com alteração da expressão do seu gene. Assim, o presente trabalho tem como objetivo investigar a possível associação de tal polimorfismo com esquizofrenia. A distribuição de seus alelos e genótipos foi investigada em uma amostra brasileira composta de 245 pacientes e 834 controles. As frequências genotípicas estavam em equilíbrio de Hardy-Weinberg e não se encontrou diferença estatisticamente significante entre casos e controles, quando analisados por gênero e subtipos da esquizofrenia. Não houve também diferença de homozigosidade entre casos e controles. Desse modo, na amostra estudada, não houve evidência de associação entre esquizofrenia e o polimorfismo rs165599 (A/G) localizado na região 3' não codificadora do gene da COMT.Palavras-Chave: enzima, gené...

Section: Discussionmentioning

confidence: 99%

Association study between the rs165599 catechol-O-methyltransferase genetic polymorphism and schizophrenia in a Brazilian sample

Cordeiro

Silva

2012

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“…In populations of highly admixed ethnicity like the Brazilian one, we may face problems about ethnical stratification 21 . Since physical phenotype in Brazil is not an adequate predictor of genomic ancestry, ethnical matching in case-controls studies is rendered difficult 22,23 . The present sample (patients and controls), however, is in Hardy-Weinberg equilibrium, which indicates that our sample may not have important problems regarding population stratification 24 .…”

Section: Discussionmentioning

confidence: 99%

Association study between the Taq1A (rs1800497) polymorphism and schizophrenia in a Brazilian sample

Cordeiro¹,

2014

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Schizophrenia is a severe psychotic disorder with recurrent relapse and functional impairment. It results from a poorly understood gene-environment interaction. The Taq1A polymorphism (located in the gene cluster NTAD) is a likely candidate for schizophrenia. Its rs1800497 polymorphism was shown to be associated with DRD2 gene expression. Therefore the present work aims to investigate a possible association between schizophrenia and such polymorphism. The compared distribution of the alleles and genotypes of the studied polymorphism was investigated in a Brazilian sample of 235 patients and 834 controls. Genotypic frequencies were in Hardy-Weinberg equilibrium. There was a trend of allelic association between the Taq1A polymorphism (rs1800497) with schizophrenia in the studied sample. However no statistically differences were found between cases and controls when analyzed by gender or schizophrenia subtypes.

Association between the SLC6A3 A1343G polymorphism and schizophrenia

Cordeiro

Siqueira-Roberto

2010

Epidemiological studies have demonstrated that the genetic component is an important risk factor for the development of schizophrenia. The genes that codify the different compounds of the dopaminergic system have created interest for molecular investigations in patients with schizophrenia because the antipsychotic drugs, especially those of first generation, act on this cerebral system. Thus the aim of the present study was to investigate the possible association between a new single nucleotide polymorphism (rs6347) located in exon 9 of the protein transporter (SLC6A3) and schizophrenia. The distribution of the alleles and genotypes of the studied polymorphism was investigated in a sample of 235 patients and 834 controls matched by gender and age. There were statistical differences in the allelic (c 2 =5.97, 1d.f., p=0.01, OR=1.33-1.05