A selective sweep takes place when a favorable mutation becomes fixed in a population. This happens in all species during the course of evolution and it happens in domestic animals as a consequence of human-driven selection for favored traits. One of the most interesting findings in this study was a striking selective sweep at the TSHR gene that codes for the thyroid-stimulating hormone receptor. In vertebrates, this protein has a key role in metabolic regulation but also in determining the timing of reproduction as a response to changes in day length, a trait that is strictly controlled in most wild animals but which is drastically altered in domestic chickens that can reproduce all year around.
"Our discovery that every domestic chicken that we have studied representing populations from Sweden to China carry a mutant form of the TSHR protein strongly suggests that this genetic change was an important step in the evolution of the domestic chicken", says Leif Andersson.
Another very convincing selective sweep was observed in broiler chickens and involved the TBC1D1 gene, a gene that has previously been associated with obesity in humans and the TBC1D1 protein is involved in the regulation of glucose uptake in muscle cells.
"Our study shows that billions of broiler chickens worldwide carry a mutant form of the TBC1D1 gene and we are now very eager to identify the causative mutation at this locus and to reveal the molecular mechanism by which it impacts growth", says Carl-Johan Rubin who was responsible for the bioinformatic analysis of selective sweeps.
The study is a breakthrough as regards genetic studies of domestic animals.
"Our study has direct implications for animal breeding and enhances the importance of the domestic chicken as a model organism for biomedical research since we can so effectively reveal genes associated with changes in phenotypic traits", concludes Leif Andersson.
|Contact: Leif Andersson|