A Comparison of Brain Gene Expression Levels in Domesticated and Wild Animals

Abstract

Domestication has led to similar changes in morphology and behavior in several animal species, raising the question whether similarities between different domestication events also exist at the molecular level. We used mRNA sequencing to analyze genome-wide gene expression patterns in brain frontal cortex in three pairs of domesticated and wild species (dogs and wolves, pigs and wild boars, and domesticated and wild rabbits). We compared the expression differences with those between domesticated guinea pigs and a distant wild relative (Cavia aperea) as well as between two lines of rats selected for tameness or aggression towards humans. There were few gene expression differences between domesticated and wild dogs, pigs, and rabbits (30–75 genes (less than 1%) of expressed genes were differentially expressed), while guinea pigs and C. aperea differed more strongly. Almost no overlap was found between the genes with differential expression in the different domestication events. In addition, joint analyses of all domesticated and wild samples provided only suggestive evidence for the existence of a small group of genes that changed their expression in a similar fashion in different domesticated species. The most extreme of these shared expression changes include up-regulation in domesticates of SOX6 and PROM1, two modulators of brain development. There was almost no overlap between gene expression in domesticated animals and the tame and aggressive rats. However, two of the genes with the strongest expression differences between the rats (DLL3 and DHDH) were located in a genomic region associated with tameness and aggression, suggesting a role in influencing tameness. In summary, the majority of brain gene expression changes in domesticated animals are specific to the given domestication event, suggesting that the causative variants of behavioral domestication traits may likewise be different.

Mining the pig genome to investigate the domestication process

“…As argued by Rubin et al (2012), few studies have been performed on early domestication traits using wild boars (Table 1), and few candidate regions have been identified. In this regard, it is worth highlighting studies on tameness in rats (Albert et al, 2009) and on the expression analysis of domestication traits in pigs, dogs and rabbits (Albert et al, 2012). These results suggest that these phenotypes correspond to complex quantitative traits that also segregate in wild populations.…”

Is evolution of domestication driven by tameness? A selective review with focus on chickens

“…For example, one study showed that a chromosomal region associated with increased tameness in Belyaev's foxes is orthologous to a domestication-related region in dogs, implying similar causal grounds in these two species (Kukekova et al, 2010). However, another study failed to find more than occasional similarities in brain gene expression differences between domesticated and wild specimens across a range of species (Albert et al, 2012). Hence, there is a need for further studies to elucidate the underlying genetic mechanisms associated with the development of the domesticated phenotype.…”

Adding ‘epi-’ to behaviour genetics: implications for animal domestication

“…For example, in a comparison of the brains of humans and chimpanzees, hundreds of genes were found to be differentially expressed (Zeng et al, 2012), and many of them were related to neural development. In an ambitious cross-species analysis, Albert et al (Albert et al, 2012) searched for brain cortexrelated gene expression signals common to domesticated mammals. Although the study did not reveal such a common signal, it was clear that the differences in gene expression appeared considerably larger than the sequence differences between pairs of domesticates and their wild ancestors.…”