The melanocortin 5 receptor gene maps to the bipolar susceptibility locus on chromosome 18p11.2. Given the biological role of melanocortins and their influence on the hypothalamic–pituitary–adrenal axis, the melanocortin 5 receptor gene is a plausible candidate gene for bipolar disorder. We tested the hypothesis that the potential functional variation Phe209Leu confers susceptibility to bipolar disorder in a case–control study.
Genotypes for two variations in the coding region and one variation approximately 7 kb upstream from the coding region were obtained from 345 unrelated bipolar I patients and 275 control samples. Genotypes and allele frequencies were compared between groups using χ2 contingency analysis.
Allele frequencies of the Phe209Leu polymorphism did not differ significantly between bipolar patients and controls (P=0.679). Allele frequencies of the C744T and the intergenic A/G polymorphism did not differ significantly between bipolar patients and controls. All variations were in strong linkage disequilibrium.
Variations in the melanocortin 5 receptor gene are unlikely to confer susceptibility to bipolar disorder in this sample. Further studies are required to elucidate the susceptibility locus for bipolar disorder on chromosome 18p11.
Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
Correspondence and requests for reprints to Falk W. Lohoff, MD, Department of Psychiatry, Center for Neurobiology and Behavior, University of Pennsylvania School of Medicine, 415 Curie Boulevard, Clinical Research Building, Room 130, Philadelphia, PA 19104-6140, USA.
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Sponsorships: Supported by National Institutes of Health Grants MH59553 and MH63876 (to W.H.B.) and R25 MH060490 (to F.W.L.), a grant from the National Alliance for Research on Schizophrenia and Depression (to W.H.B.) and the Tzedakah Foundation (to W.H.B.).
Received 18 December 2003 Accepted 15 February 2004