RESUMO
The genetic factors that increase risk for alcohol and nicotine addiction have been elusive, although the frequent co-abuse of these drugs suggests they may act on a common biological pathway. A site of action for both nicotine and alcohol effects in the brain are neuronal nicotinic acetylcholine receptors (nAChR). This report explores the association between six nAChR subunit genes (Chrna3, Chrna4, Chrnb4, Chrnb2, Chrna5, and Chrna7) with alcohol preference (AP) using co-segregation of AP with nAChR subunit genotypes in a F(2) population produced from reciprocal crosses of alcohol-preferring C57BL/6J (B6) and alcohol-avoiding DBA/2J (D2) strains of mice. Polymorphisms located within the Chrna5-Chrna3-Chrnb4 cluster on mouse chromosome 9 were found to co-segregate with AP, with high-drinking F(2) mice carrying B6 alleles and low-drinking F(2) mice carrying D2 alleles. Further, the Chrnb4 and Chrna5 genes showed expression differences between B6 and D2 mice, which is compatible with their involvement in AP in mice and, potentially, alcohol abuse in humans.
Assuntos
Consumo de Bebidas Alcoólicas/genética , Proteínas do Tecido Nervoso/genética , Receptores Nicotínicos/genética , Consumo de Bebidas Alcoólicas/metabolismo , Animais , Encéfalo/metabolismo , Cromossomos de Mamíferos/genética , Cruzamentos Genéticos , Etanol/farmacologia , Feminino , Genótipo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Polimorfismo Genético , Receptor Nicotínico de Acetilcolina alfa7RESUMO
BACKGROUND: Previously, our group identified cytotoxic and regulatory T-cell molecule (Crtam), zinc finger and BTB domain containing 16 (Zbtb16), and myelin-associated oligodendrocytic basic protein (Mobp) as ethanol-responsive genes in the mouse brain by gene expression profiling. In this study, we used a genetic co-segregation analysis to assess the association of Crtam, Zbtb16, and Mobp with the alcohol preference (AP) phenotype in the alcohol-preferring C57BL/6J (B6) and alcohol avoiding DBA/2J (D2) strains of mice. METHODS: Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to confirm previous microarray analysis results that Crtam, Zbtb16, and Mobp brain mRNA levels in the B6 and D2 strains are altered by ethanol treatment. The association of the 3 genes with AP was assessed in a F(2) population (n = 427) derived from the reciprocal crosses involving the B6 and D2 strains. Each F(2) individual was assessed for their AP using the 2 bottle choice test and genotyped for Crtam, Zbtb16, and Mobp single nucleotide polymorphisms (SNPs) that differ between B6 and D2 mice. RESULTS: Semi-quantitative RT-PCR analysis confirmed that Crtam, Zbtb16, and Mobp are ethanol-responsive genes. The SNP analyses show that alleles of the 3 genes co-segregate with the AP phenotype in F(2) mice, where individuals homozygous for the B6 allele have higher AP than those homozygous for the D2 allele. Also, the Crtam-Zbtb16 loci that are tightly linked and the Mobp locus act in an additive fashion in determining the relative AP phenotype. CONCLUSION: Our results are consistent with the hypothesis that Crtam, Zbtb16, and Mobp may be involved in AP in mice. The nature of this association remains to be established and may reflect a direct effect of these genes or an indirect effect caused by linked genes on mouse chromosome 9.
Assuntos
Consumo de Bebidas Alcoólicas/genética , Cromossomos de Mamíferos/genética , Etanol/administração & dosagem , Imunoglobulinas/genética , Fatores de Transcrição Kruppel-Like/genética , Glicoproteína Associada a Mielina/genética , Locos de Características Quantitativas/genética , Animais , Cruzamentos Genéticos , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Proteínas da Mielina , Glicoproteína Mielina-Oligodendrócito , Proteína com Dedos de Zinco da Leucemia PromielocíticaRESUMO
BACKGROUND: Inwardly-rectifying potassium channel protein Kir4.1 is encoded by Kcnj10 which maps to a quantitative trait locus on chromosome 1 for the voluntary alcohol consumption phenotype in mice. Kcnj10 brain expression differences have been established between ethanol-preferring C57Bl/6J and ethanol-avoiding BALB/cJ mice, but its differential expression in other tissues and strains have largely been overlooked. A nonsynonymous single nucleotide polymorphism exists between C57Bl/6J and ethanol-avoiding DBA/2J mice which changes amino acid 262 from threonine (C57Bl/6J) to serine (DBA/2J). This Kcnj10 SNP and its expression may serve as valuable markers in predicting the ethanol preference phenotype in mice. METHODS: The evolutionary divergence of the Kir gene family was characterized using phylogenetic analysis involving the 16 mouse Kir channels. Kcnj10 expression differences in the brain, liver, lung, heart, spleen, kidney, testes, and muscle of male C57Bl/6J and DBA/2J mice at different developmental stages were examined using semiquantitative RT-PCR analysis. A SNP analysis was conducted to assess the association of Kcnj10 Thr262Ser SNP and the ethanol preference phenotype in F2 mice derived from the reciprocal crosses of the C57Bl/6J and DBA/2J strains. RESULTS: Evolutionary analysis supports gene duplication and genetic recombination as likely sources of diversity within the Kir gene family. Semiquantitative RT-PCR analysis revealed significantly higher Kcnj10 expression in the brain, spleen, and kidney of both strains when compared to other tissues from the same strain. There were no significant differences in tissue-specific mRNA levels between strains except in the testes. Genotype distributions of the Kcnj10 Thr262Ser SNP were different between low- and high-drinkers. A significant difference in the average ethanol preference level of each genotype was also observed. CONCLUSION: Our results suggest a role for Kcnj10 in ethanol preference determination in mice. However, further experiments are needed to establish if this association is due to the nonsynonymous SNP or other additional factors associated with Kcnj10.
