Molecular characterization of new polymorphisms at the β2, α1, γ2 GABA A receptor subunit genes associated to a rat nonpreferring ethanol phenotype

Abstract

Recent preclinical and clinical studies have indicated a possible involvement of the genes encoding for the GABA A receptor subunits α6, β2, α1 and γ2 in the genetic susceptibility to alcohol abuse. We have recently found an (R) to (Q) mutation in codon 100 of the α6 GABA A subunit, that segregated in a rat line selectively bred for its voluntary ethanol aversion, Sardinian alcohol nonpreferring (sNP), but not in their Sardinian alcohol preferring (sP) counterpart, selected for its ethanol preference. In the present study the molecular composition of other GABA A subunits (β2, α1 and γ2) were analyzed in order to further investigate the involvement of the GABA A receptors in the genetic predisposition to voluntary alcohol intake. Automated sequencing analysis indicated the presence of six new silent substitutions (289 T→C in the β2 gene; 115 G→A in the α1 gene; 157 G→A, 174 C→T, 347 A→G and 385 A→T in the γ2 gene), in sNP but not in sP rats. These polymorphisms were linked to the α6 R100Q mutation previously described in sNP rats. The strict association between the α6 point mutation and the new polymorphisms found in the β2, α1 and γ2 genes, demonstrate that such genes belong to the same cluster and are inherited together in the rat. These results sustain the synteny for these clusters between the rodent and human genomes, and suggest that mutated GABA A β2, α6, α1 and γ2 subunit genes might contribute to the expression of an ethanol nonpreferring phenotype in a rat line that voluntarily avoids alcoholic solutions.