No evidence for involvement of polymorphisms of the dopamine D4 receptor gene in anorexia nervosa, underweight, and obesity

Family and twin studies suggest a genetic contribution to the etiology of anorexia nervosa (AN) and obesity. Genes involved in weight regulation can be considered as candidate genes for AN. The dopaminergic system has been implicated in weight regulation; previous results had suggested a possible involvement of the dopamine D4 receptor gene (DRD4). We screened for alleles of two different polymorphisms (13-bp deletion, 48-bp repeat) in the DRD4. For association tests, allele frequencies were compared between 109 inpatients with AN, 82 underweight students, and 327 extremely obese children and adolescents. For application of transmission disequilibrium tests (TDT) we additionally genotyped 57 and 137 trios comprising a patient with AN or an extremely obese child or adolescent, respectively, and both parents. All genotyping was performed with polymerase chain reaction fragment length polymorphism analyses. None of the association tests or TDT rendered nominal P values below 0.1. An influence of alleles of the DRD4 on the development of AN, underweight, or extreme early onset obesity was not detected.