Birgit Wendel

Association of a CB1 Cannabinoid Receptor Gene (CNR1) polymorphism with severe alcohol dependence

Due to the involvement of the endogenous cannabinoid system in brain reward mechanisms a silent polymorphism (1359G/A; Thr453Thr) in the single coding exon of the CB1 human cannabinoid receptor gene (CNR1) was analysed in 121 severely affected Caucasian alcoholics and 136 most likely non-alcoholic controls. The observed frequency of the A allele was 31.2% for controls and 42.1% for alcoholics with severe withdrawal syndromes (P=0.010). Post-hoc exploration indicated that this allelic association resulted from an excess of the homozygous A/A genotype in patients with a history of alcohol delirium (P=0.031, DF 2), suggesting s an increased risk of delirium (OR=2.45, 95% CI 1.14--5.25). This finding suggests that the homozygous genotype CNR1 1359A/A confers vulnerability to alcohol withdrawal delirium.

The human µ opioid receptor gene: 5´ regulatory and intronic sequences

Abstract The human µ opioid receptor (hMOR) interacts with endogenous and exogenous ligands to mediate its characteristic effects, reward, dependence, and analgesia. Specifically binding morphine, it represents the target of the most valuable pain killer in contemporary medicine. Analysis of its structure, regulation, and expression will elucidate molecular processes involved in opioid/morphine-induced actions. Thus we have contributed significant information on the genomic organization of hMOR, extending the previously known cDNA sequence information (2162 bp) up to a total of 6968 bp: we have determined 2412 bp of 5´ regulatory region, identified one major and three minor transcription initiation sites 216, 285, 358, and 373 bp upstream from the translation start codon, as well as potential binding sites for transcriptional regulatory factors, including putative cis-acting enhancer motifs for a glucocorticoid response element, cAMP response elements, activator proteins 1, and Yin Yang-1 boxes. Moreover, we have analyzed the 5´ and 3´ nucleotide sequences of introns 1 and 3 and the complete sequence of intron 2. In addition to the classical consensus sequences involved in RNA splicing, we have identified intronic repeats (A/TGGG) found to regulate alternative splicing, mutations of which cause human disease. A similar genetic variant is observed in the hMOR gene. Taken together, the sequence information presented will allow comprehensive analysis of this gene for allelic variations associated with vulnerability to drug abuse or individual differences in opiate mediated analgesia.

μ-Opioid receptor variants and dopaminergic sensitivity in alcohol withdrawal

OBJECT The endogenous opioid system plays an important role in the reinforcing properties of alcohol by an interconnected activation of the mesolimbic dopamine system. The Asn40Asp substitution polymorphism of the human mu-opioid-receptor (OPRM) influences binding of opioids and signal transduction and may, thereby, contribute to the development of alcoholism. The present study tested whether the Asn40Asp substitution polymorphism of the OPRM gene is associated with a variation in central dopaminergic sensitivity during alcohol withdrawal in alcoholics. METHOD Sensitivity of central dopamine receptors was assessed by apomorphine-induced growth hormone (GH) secretion in 97 alcohol-dependent patients before and 1 week after alcohol cessation, and in a subgroup of 19 alcoholics after 3 months of abstinence. GH response was defined as area under the hormone/time curve. Comparisons of the GH response were conducted between alcoholics carrying the Asn40Asp genotype versus those with the Asn40Asn genotype using U-test statistics. RESULTS Marginal differences in apomorphine-induced GH response were found between both genotype groups before detoxification (P = 0.799 (n = 97)/P = 0.459 (n = 19)) and after 3 months of abstinence (P = 0.331 (n = 19)). In contrast, the GH response measured seven days after alcohol withdrawal was significantly increased in alcoholics with the Asn40Asp genotype compared with those carrying the Asn40Asn genotype (P = 0.013 (n = 97)/P = 0.026 (n = 19)). CONCLUSION Our results suggest that genetic variation of the mu-opioid receptor modulates the central dopaminergic sensitivity during acute alcohol withdrawal.

Genetic variation of the human μ-opioid receptor and susceptibility to idiopathic absence epilepsy

Pharmacological and autoradiological studies suggest that mu-opioid receptor (OPRM) mediated neurotransmission is involved in the generation of absence seizures. Mutation screening of the human OPRM gene identified a common amino acid substitution polymorphism (Asn40Asp) that differentially modulates the binding affinity of beta-endorphin and signal transduction of the receptor. The present association study tested the candidate gene hypothesis that the Asn40Asp substitution polymorphism in the N-terminal OPRM domain confers genetic susceptibility to idiopathic absence epilepsy (IAE). The genotypes of the Asn40Asp polymorphism were assessed by allele-specific polymerase chain reaction in 72 German IAE patients and in 340 ethnically matched control subjects. The frequency of the Asp40 allele was significantly increased in the IAE patients [f(Asp40) = 0.139] compared to the controls [f(Asp40) = 0.078; chi2 = 5.467, df = 1, P = 0.019; OR = 2.03; 95%-CI: 1.12-3.68]. This allelic association suggests that the functional Asp40 variant of OPRM modulates neuronal excitability underlying the epileptogenesis of IAE.

The human β-myosin heavy chain gene: Sequence diversity and functional characteristics of the protein

The β‐myosin heavy chain gene (MYH7) encodes the motor protein that drives myocardial contraction. It has been proven to be a disease gene for hypertrophic cardiomyopathy (HCM). We analyzed the DNA sequence variation of MYH7 (about 16 kb) of eight individuals: six patients with HCM and two healthy controls. The overall DNA sequence identity was up to 97.2% compared to Jaenicke and coworkers (Jaenicke et al. [1990] Genomics 8:194–206), while the corresponding amino acid sequences revealed 100% identity. In HCM patients, eleven nucleotide substitutions were identified but no causative disease mutation was found: six were detected in coding, four in intronic, and one in 5′ regulatory regions. The average nucleotide diversity across this locus was 0.015% with an average of 0.02% in the coding and 0.012% in the noncoding sequence. Analysis of the kinetic behaviour of β‐MHC in the intact contractile structure of normal individuals and HCM patients revealed apparent rate constants of tension development ranging between 1.58 s−1 and 1.48 s−1. J. Cell. Biochem. 79:566–575, 2000.