Analysis of the polymorphic (GT)(n) repeat at the dopamine beta-hydroxylase gene in Spanish patients affected by schizophrenia

The presence of a polymorphic (GT)(n) repeat, a microsatellite repeat, at t he human dopamine beta-hydroxylase (DBH) gene had been previously investiga ted in healthy people and in schizophrenic patients. The different DBH geno types had been found to be associated to different DBH biochemical function , but no differences were found in the allelic and genotype frequencies bet ween schizophrenic and control groups. To further clarify the potential inv olvement of the variation at the DBH gene in schizophrenia we have studied the DBH (GT)(n) repeat in a sample of 47 Spanish schizophrenic patients, in their healthy relatives (n = 72), and in a control population (n = 74), We have been able to identify five different variants of the DBH gene (A1, A2 , A3, A4, A5) in the different groups. Subsequent statistical analysis reve aled that the genotypes as well as the allele frequencies did not differ si gnificantly among schizophrenic patients and the control population. Intere stingly, the allelic variant A2 and the genotype A4/ A2 were significantly more frequent in schizophrenic patients as compared with their healthy rela tives. However, the association of the A2 allele with schizophrenia was not supported by the haplotype relative risk analysis of transmitted versus no ntransmitted alleles. Therefore, although it will be important to extend th e present analysis in a larger sample of schizophrenic patients and control s, our results suggest that the (GT)(n) does not seem to play a major role in the genetics of schizophrenia at least in this group of Spanish schizoph renic patients. Am. J, Med. Genet. (Neurorpsychiatr. Genet.) 96:88-92,2000, (C) 2000 Wiley-Liss, Inc.