Linkage and association of a functional DRD2 variant [Ser311Cys] and DRD2 markers to alcoholism, substance abuse and schizophrenia in Southwestern American Indians.

Alcoholism is one of a group of common psychiatric diseases which are well-defined clinically and strongly influenced genetically, but which are likely to be highly heterogeneous in causation, genetically and otherwise. Dopamine is a key neurotransmitter in drug-mediated reinforcement. Based on association studies with the Taq1A downstream marker, the D2 dopamine receptor has been proposed to be the "Reward Deficiency Syndrome Gene." Ser311Cys, a naturally occurring variant which largely inactivates transduction after D2 receptor activation, was abundant (0.16) in a Southwestern American Indian population we studied. Therefore, we were able to provide a critical test of the D2 hypothesis of vulnerability to alcoholism by evaluating Ser311Cys and also the intron-2 STR and Taq1A markers at this locus in a total of 459 subjects, including 373 sib pairs, from large families. The result is that neither alcoholism, substance use disorders nor schizophrenia show a relationship to Ser311Cys genotype, even when the 15 Cys311/Cys311 homozygous individuals are compared to others. Furthermore, sib pair analysis incorporating information across all three sib pair categories: concordant affected, discordant and concordant unaffected revealed no effect of DRD2 genotype or haplotype on alcoholism or substance use disorder.