[Schizophrenia and dopamine D4 gene polymorphism in Chinese population: association analysis].

OBJECTIVE

To investigate the association of the 48 bp variable number tandem repeat (VNTR) polymorphism in the dopamine D4 receptor (DRD4) gene exon III with schizophrenia in Chinese Han population.

METHODS

Case-control association study was adopted to analyze the association between the 48 bp VNTR polymorphism of DRD4 gene exon III in 510 DSM-IV schizophrenics and 171 psychiatrically normal controls.

RESULTS

(1) The DRD4 gene 48 bp VNTR polymorphism was manifested as 2-7 repeats, with the 4 repeats the most common (78.6% in schizophrenics and 76.9% in controls respectively). The frequency of 2 repeats was 16.2% and 19.3% in the schizophrenics and controls respectively. (2) The genotypic frequency was statistically significantly different between the schizophrenics and the controls. The genotypic frequency of short tandem repeats (2/2 and 2/3 genotype) was lower in patients (3.3%) than in controls (10.5%) (chi 2 = 14.88, df = 2, P = 0.00). (3) the frequency of the genotype with 4-repeat allele in patients was higher (95.9%) than in controls (88.3%) (chi 2 = 13.00, df = 1, P = 0.000).

CONCLUSION

The most common allele in Chinese schizophrenics was 4 repeats in the 48 bp VNTR polymorphism of DRD4 gene exon III. The repeat number of 48 bp is probably associated with schizophrenia. Lack of 2-3 repeats or excess of genotype with 4-repeat allele may be associated with increased vulnerability to schizophrenia.