The -141C Ins/Del polymorphism of the dopamine D2 receptor gene is not associated with either migraine or Parkinson's disease

Abnormalities in dopamine neurotransmission at the dopamine D2 receptor (DRD2) have been implicated in both migraine and Parkinson's disease. Positive associations have also been found between polymorphisms within the DRD2 gene and both of these conditions. The -141C Ins/Del polymorphism in the DRD2 receptor gene is a putative functional polymorphism. The purpose of this study was to determine whether it and any genes in linkage disequilibrium with this marker are involved in either of these conditions. We have compared the genotype and allele frequencies of the -141C Ins/Del polymorphism in 200 migraineurs and 260 Parkinson's disease cases with 464 controls. We have found no association between the receptor gene and either condition (P = 0.89 and P = 0.56 respectively). Our findings do not support the hypothesis that this polymorphism is involved in the aetiology of migraine or Parkinson's disease.

-141 C del/ins polymorphism of the dopamine receptor 2 gene is associated with schizophrenia in a British population

Dopamine has long been hypothesised to be involved in the pathogenesis of schizophrenia. The dopamine D2 receptor is a major site of action of neuroleptic agents used in the treatment of schizophrenia. Arinami et al. [1997; Human Mol Genet 6:577-582] have recently sequenced the dopamine receptor 2 (DRD2) gene in Japanese individuals and identified a novel polymorphism: a single cytosine deletion at position -141 disrupting a BstN1 restriction site with a frequency of 0.22 in their control group. They then found a strong association with this polymorphism and schizophrenia (p < 0.001) with an odds ratio of 0.60 in a Japanese population. We have attempted to verify their results by repeating the RFLP analysis on a sample of Scottish schizophrenics and controls. We then combined our data with those from another British sample recruited using similar procedures. The total combined sample size was 439 schizophrenics and 437 controls. We obtained a significant association--p = 0.02 with an odds ratio of 1.41. Schizophrenia is associated with the C insertion in the Japanese, but that association is reversed in Caucasians. Linkage disequilibrium with a causative polymorphism nearby is the most likely explanation for this reverse association.