Meta-analysis of Genome Wide Association and Gene Expression Studies to Identify Candidate Genes for Tick Burden in Cattle

The cattle tick is endemic throughout some of the most productive cattle growing regions in the world, with a higher incidence in tropical and subtropical areas (Barker & Murrell 2004). Ticks and tick borne diseases are responsible for large losses in livestock productivity (Jongejan & Uilenberg 2004), estimated to be around 18 billion dollars per year globally (de Castro 1997). Genome wide association studies (GWAS) and gene expression studies (GES) are two approaches being applied to study the tick-host interaction to understand the biological processes involved with host immune responses to tick infestation, and to identify genomic regions associated with tick burdens. Very few markers in single nucleotide polymorphism (SNP) GWAS are functional mutations. Primarily the markers serve to indicate genomic regions that have a significant association with the trait in question. In GES the relative abundance of specific mRNA transcripts are estimated to gain insights into the biological/molecular processes taking place in vivo. A meta-analysis combining both approaches could potentially give more robust predictions adding biological information into the GWAS and reducing the background noise of expression arrays used in GES. Here we present a meta-analysis combining both approaches to the case study of tick resistance.