DRD5 microsatellite marker shows significant association with schizophrenia in 3 discrete Scottish schizophrenic populations

A case-control study demonstrated a significant increase (p=0.024) in the frequency of the 148bp allele of the DRD5 microsatellite marker that maps to the D5 dopamine receptor locus, in patients with schizophrenia from South-east Scotland (n=158) compared with controls without psychiatric illness (n=437) 1. We have tested the reproducibility of this finding and examined the possibility that the significant association may be due to the effects of popula-tion stratification, we compared data from the previously described group with a distinct population of schizophrenic patients from Central Scotland (n=109). We studied schizophrenics resident in the State Hospital at Carstairs (n=96) as an independent sample set. We hypothesis that they may represent a distinct group of psychiatric patients, thus we typed the DRD5 microsatellite to test whether this group exhibits differential distribution of alleles to that of the general schizophrenic population. Participating patients from Central Scotland and Carstairs Hospital Scotland gave full informed consent; DSM-IV and RDC diagnosis of definite schizophrenia was reached using SADS-L criteria. DNA was obtained from venous blood by standard methods, the DRD5 repeat polymorphism was PCR amplified and electrophoresis carried out using automated laser fluorescence (ALF) and analyzed using AlleleLinks program (Amersham Pharmacia Biotech). Results indicate that patients with schizophrenia from Central Scotland demonstrate a similar increased distribution of 148bp alleles (p=0.022) compared to control subjects, and thus lends support to the data obtained from the original sample. Initial results obtained from in-patients of Carstairs State Hospital indicate that the frequency of the 148bp allele is increased to an identical extent and therefore this group does not differ from the general schizophrenic population with respect to this marker.