A broad goal of this Center is to combine the use of Quantitative Trait Loci (QTL) linkage mapping techniques with several different animal genetic models to identify and localize genes affecting behavioral and pharmacological responses to ethanol. Our previous studies have revealed substantial genetic variability within the BXD recombinant inbred strains in three different ethanol phenotypes believed to be relevant to understanding the rewarding and aversive effects of ethanol: ethanol drinking, conditioned place preference, and conditioned taste aversion. Moreover, our studies suggest partial overlap in the genetic mechanisms influencing these behaviors and QTL analyses have identified several chromosomal regions of potential interest. However, because of limitations imposed by the statistical strategy used for QTL mapping, these loci must be considered provisional until they are confirmed by additional studies. Thus, the goal of this Component Project is to verify several of the strongest QTL identified for each of these ethanol reward phenotypes (e.g., withdrawal, hypothermia, ataxia). Our primary strategy for QTL verification involves testing of F2 mice derived from the BXD progenitor strains, C57BL/6 (B6 and DBA/2 (D2), and genotyping high responders and low responders at markers flanking the provisional QTL. The importance of QTL verified in this population will be evaluated further in studies in which F2 mice are selectively bred on the basis of their genotype at markers flanking a verified QTL (Genotypic Selection). These mice will then be tested for differences in the behavioral phenotypes to determine the role of allelic status at the QTL of interest. Genotypic selection will also sere as the starting point for the development of Congenic Strains in which either the B6 or D2 allele at a target QTL is transferred to the background of the opposite progenitor strain by repeated backcrossing. These oncogenic strains will facilitate future research aimed at identifying specific genes influencing each behavioral phenotype. Finally, to evaluate the genetic interrelatedness of these behavioral phenotypes, we will examine correlated responses to selection in mouse lines that have been selectively bred for differences in sensitivity to ethanol' behavioral effects in each of these tasks (Phenotypic Selection). These selected liens will also be genotyped at appropriate markers to determine whether divergence in the behavioral phenotype is accompanied by divergence in gene frequency. Once candidate genes have been identified in the mouse, homologous genes or regions of the human chromosome can be studied in detail to determine whether they are linked to alcoholism.
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