Fine mapping and expression of candidate genes within the chromosome 10 QTL region of the high and low alcohol-drinking rats

The high and low alcohol-drinking (HAD and LAD) rats were selectively bred for differences in alcohol intake. The HAD/LAD rats originated from the N/Nih heterogeneous stock developed from intercrossing eight inbred rat strains. The HAD × LAD F2 were genotyped, and a powerful analytical approach, using ancestral recombination and F2 recombination, was used to narrow a quantitative trait loci (QTL) for alcohol drinking to a 2-cM region on distal chromosome 10 that was in common in the HAD1/LAD1 and HAD2/LAD2 analyses. Quantitative real-time PCR was used to examine mRNA expression of six candidate genes (Crebbp, Trap1, Gnptg, Clcn7, Fahd1, and Mapk8ip3) located within the narrowed QTL region in the HAD1/LAD1 rats. Expression was examined in five brain regions, including the nucleus accumbens, amygdala, caudate putamen, hippocampus, and prefrontal cortex. All six genes showed differential expression in at least one brain region. Of the genes tested in this study, Crebbp and Mapk8ip3 may be the most promising candidates with regard to alcohol drinking.