Redefinition of the human kappa opioid receptor gene... : Pharmacogenetics and Genomics (original) (raw)

ORIGINAL ARTICLES

Redefinition of the human kappa opioid receptor gene (OPRK1) structure and association of haplotypes with opiate addiction

Yuferov, Vadima; Fussell, Davida; LaForge, K Stevena; Nielsen, David Aa; Gordon, Derekb; Ho, Anna; Leal, Suzanne Mb,c; Ott, Jurgb; Kreek, Mary Jeannea

aLaboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, bLaboratory of Statistical Genetics, The Rockefeller University, New York, NY and cDepartment of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Sponsorship: This study was supported by the National Institutes of Health (NIH) National Institute on Drug Abuse grants K05-DA00049 (M.J.K.), DA12848 (M.J.K.); NCRR General Clinical Research Center grant M01-RR00102; K01-HG00055 (D.G.); and MH44292 (J.O.).

Correspondence and requests for reprints to Vadim Yuferov, Laboratory of the Biology of Addictive Diseases, The Rockefeller University, Box 171, 1230 York Avenue, New York, NY 10021, USA. Tel: +1 212 327 8234; fax: +1 212 327 8574; e-mail: [email protected]

Received 21 December 2003 Accepted 23 August 2004

Abstract

The kappa opioid receptor (KOR) plays a role in stress responsivity, opiate withdrawal and responses to cocaine. KOR activation by its endogenous ligand dynorphin A(1-17) decreases basal and drug-induced striatal levels of dopamine. The complete structure of the human KOR gene (h_OPRK1_) has not been previously determined. This study: (i) characterized the genomic structure of the h_OPRK1_ gene; (ii) identified single nucleotide polymorphisms (SNPs) in the h_OPRK1_ gene; and (iii) investigated possible associations of these variants with vulnerability to develop heroin addiction. Analysis of 5′-RACE cDNA clones revealed the presence of a novel exon 1 ranging in length from 167 to 251 nucleotides in the 5′ 5′-untranslated region of the h_OPRK1_ mRNA. We found that the h_OPRK1_ gene has four major exons and three introns, similar to rodent OPRK1 genes. Direct sequencing of amplified DNA containing all four exons and intron 1 of the h_OPRK1_ gene were evaluated for polymorphisms in 291 subjects (145 former heroin addicts and 146 controls). Twelve SNPs were identified, nine novel variants and three previously reported SNPs. Using logistic regression with opioid dependence as the dependent variable, the 36G>T SNP exhibited a point-wise significant association (P = 0.016) with disease status. The number of haplotypes seen in the three ethnic groups were nine, six and five for African-Americans, Caucasians, and Hispanics, respectively, with corresponding significance levels for differences in haplotype frequencies between cases and controls of P = 0.0742, 0.1015 and 0.0041. Combining ethnicities by Fisher's method yields an empirical significance level of P = 0.0020.