Quantitative Trait Loci Affecting Initial Sensitivity and Acute Functional Tolerance to Ethanol-Induced Ataxia and Brain cAMP Signaling in BXD Recombinant Inbred Mice

Abstract

In previous work, we identified genetic correlations between cAMP accumulation in the cerebellum and sensitivity to the incoordinating effects of ethanol. A genetic correlation suggests that common genes underlie the phenotypes investigated. One method for provisionally identifying genes involved in a given phenotypic measure is quantitative trait locus (QTL) analysis. Using a panel of 30 BXD recombinant inbred strains of mice and the progenitors (DBA/2J and C57BL/6J), and the dowel test for ataxia, we measured the blood ethanol concentrations at the time an animal first fell from the dowel and acute functional tolerance (AFT), and investigated cAMP signaling in the cerebellum. Cyclic AMP accumulation was measured in whole-cell preparations of cerebellar minces from individual mice under basal or stimulated conditions. We conducted a genome-wide QTL analysis of the behavioral and biochemical measures with Ͼ2000 genetic markers to identify significant associations. Western blot and comparative sequencing analysis were used to compare cAMP response element binding protein (CREB) levels and protein-coding sequence, respectively. QTL analyses correlating strain means with allelic status at genetic markers identified several significant associations (p Ͻ 0.01). Analysis of variance revealed an effect of strain on behavioral and biochemical measures. There was a significant genetic correlation between initial sensitivity and basal cAMP accumulation in the cerebellum. We identified 6 provisional QTLs for initial sensitivity on four chromosomes, 6 provisional QTLs for AFT on four chromosomes, and 11 provisional QTLs for cAMP signaling on nine chromosomes. Two loci were found to overlap for measures of initial sensitivity and for cAMP signaling. Given the genetic correlation between initial sensitivity and basal cAMP accumulation, we investigated candidate genes in a QTL on chromosome 1. Comparative sequence analysis was performed, and protein levels were compared between C57 and DBA mice for Creb1. No significant differences were detected in coding sequence or protein levels for CREB. These results suggest that although ethanol sensitivity and cAMP signaling are determined by multiple genes, they may share certain genetic codetermination.

Genetic regulation of hypothalamic cocaine and amphetamine-regulated transcript (CART) in BxD inbred mice

“…This location is in close proximity to the GABA A receptor gene and a series of QTL associated with ethanol and pentobarbital dependence and withdrawal severity in BxD mice (Buck et al 1998(Buck et al , 1999. This region is also implicated in initial sensitivity to ethanol (Kirstein et al 2002).…”

Genomic Insights into Acute Alcohol Tolerance

“…We have previously published the data on the measures of AFT in the 30 strains of BXD mice and the parental strains (Kirstein et al, 2002) and in two replicate selectively bred lines of mice (HAFT1 and LAFT1, HAFT2 and LAFT2) (Saba et al, 2006). In the present study, we measured AFT in the 20 inbred strains of mice using the same dowel test as used previously.…”

“…These Reanalysis of AFT bQTLs Using BXD RI Mice. AFT bQTLs were previously determined in our laboratories using 30 BXD strains and two parental strains (Kirstein et al, 2002). We were able to use more markers together with the behavioral AFT data that we published previously to redetermine AFT bQTLs.…”

“…The genetic influence on AFT in this particular test is demonstrated by studies of inbred and recombinant inbred (RI) mouse strains (Kirstein et al, 2002), as well as by successful selective breeding of low AFT (LAFT) and high AFT (HAFT) mouse lines (Erwin and Deitrich, 1996). Heritability for AFT has been estimated to range from 0.25 to 0.39 (Kirstein et al, 2002;Bennett et al, 2007).…”

“…The genomic locations that contribute to AFT have been mapped using quantitative trait locus (QTL) analysis in 30 BXD RI strains and the progenitor strains (Kirstein et al, 2002). However, specific genes contributing to AFT are still unknown.…”