Extensive genetic and genomic studies of the relationship between alcohol drinking preference and withdrawal severity have been performed using animal models. Data from multiple such publications and public data resources have been incorporated in the GeneWeaver database with .60,000 gene sets including 285 alcohol withdrawal and preference-related gene sets. Among these are evidence for positional candidates regulating these behaviors in overlapping quantitative trait loci (QTL) mapped in distinct mouse populations. Combinatorial integration of functional genomics experimental results revealed a single QTL positional candidate gene in one of the loci common to both preference and withdrawal. Functional validation studies in Ap3m2 knockout mice confirmed these relationships. Genetic validation involves confirming the existence of segregating polymorphisms that could account for the phenotypic effect. By exploiting recent advances in mouse genotyping, sequence, epigenetics, and phylogeny resources, we confirmed that Ap3m2 resides in an appropriately segregating genomic region. We have demonstrated genetic and alcohol-induced regulation of Ap3m2 expression. Although sequence analysis revealed no polymorphisms in the Ap3m2-coding region that could account for all phenotypic differences, there are several upstream SNPs that could. We have identified one of these to be an H3K4me3 site that exhibits strain differences in methylation. Thus, by making cross-species functional genomics readily computable we identified a common QTL candidate for two related bio-behavioral processes via functional evidence and demonstrate sufficiency of the genetic locus as a source of variation underlying two traits.
FINDING the genetic and genomic basis for complex disorders has been a major challenge, particularly for behavioral traits. This is because the disorders are highly heterogeneous in their manifestation and regulation, requiring a match of numerous genes to many aspects of the disorders. A compelling approach to this problem lies in integration of numerous disparate data sets across species, each aimed at characterizing the mechanistic biological underpinnings for the behaviors underlying these disorders as modeled in various species. Alcoholism and alcohol use-related disorders are complex, heritable traits that have been the subject of extensive genomic and genetic investigations (Morozova et al. 2012). These traits are particularly challenging because of their heterogeneity and the presence of multiple overlapping subsystems that subserve them (Gould and Gottesman 2006;Crabbe 2012). Many rodent quantitative trait loci (QTL) have been mapped for alcohol-related traits (Ehlers et al. 2010), gene expression analyses have been performed in a variety of populations, and a long history of alcoholism genetics in humans has led to numerous genome-wide association studies (GWAS) or linkage studies (Enoch 2013). QTL mapping studies historically had very low resolution, and many have been performed using populations for which...