Allelic Variation in the GABAA Receptor γ2 Subunit Is Associated With Genetic Susceptibility to Ethanol‐Induced Motor Incoordination and Hypothermia, Conditioned Taste Aversion, and Withdrawal in BXD/Ty Recombinant Inbred Mice

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Abstract
Background: Behavioral genomics has made dramatic progress toward mapping quantitative trait loci (QTLs) that contain genes responsible for phenotypic differences in a variety of behavioral responses to alcohol (ethanol). We previously identified a QTL on mouse Chromosome 11 that affects genetic predisposition to acute alcohol withdrawal. Among mice derived from the C57BL/6J (B6) and DBA/2J (D2) inbred strains, this QTL (Alcw3) accounts for 12% of the genetic variability in withdrawal liability. Candidate genes within this QTL encode the γ‐aminobutyric acid type A (GABAA) receptor γ2, α1, α6, and β2 subunits. We recently identified a coding sequence polymorphism between the B6 and D2 strains for the GABAA receptor γ2 subunit gene (Gabrg2). In this study, we expand our analysis to a panel of BXD strains derived from the B6 and D2 progenitor strains. These BXD strains provide 26 fixed recombinant genotypes that can be used to examine genetic correlations, for example, between a phenotype of interest and allelic variation in a candidate gene.Methods: Gabrg2 was cloned and sequenced from the 26 BXD recombinant inbred strains. We analyzed genetic correlations between allelic variation in Gabrg2 and alcohol phenotypes previously measured in the BXD strain means.Results: Allelic variation in Gabrg2 is correlated genetically with predisposition to acute alcohol withdrawal and may underlie the Alcw3 locus. In addition, Gabrg2 is associated with ethanol‐conditioned taste aversion, ethanol‐induced motor incoordination, and ethanol‐induced hypothermia. A trend is observed for chronic ethanol withdrawal, ethanol‐induced loss of righting reflex, and tolerance to ethanol‐induced hypothermia and ataxia.Conclusions: Functionally relevant variation in Gabrg2, or a closely linked gene, is correlated genetically with some, but not all, behavioral responses to alcohol. The alcohol‐related phenotypes associated with Gabrg2 generally may be characterized as debilitating or motivationally negative.

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