Convergent molecular evolution of thermogenesis and circadian rhythm in Arctic ruminants

The muskox and reindeer are the only ruminants that have evolved to survive in harsh Arctic environments. However, the genetic basis of this Arctic adaptation remains largely unclear. Here, we compared a de novo assembled muskox genome with reindeer and other ruminant genomes to identify convergent amino acid substitutions, rapidly evolving genes and positively selected genes among the two Arctic ruminants. We found these candidate genes were mainly involved in brown adipose tissue (BAT) thermogenesis and circadian rhythm. Furthermore, by integrating transcriptomic data from goat adipose tissues (white and brown), we demonstrated that muskox and reindeer may have evolved modulating mitochondrion, lipid metabolism and angiogenesis pathways to enhance BAT thermogenesis. In addition, results from co-immunoprecipitation experiments prove that convergent amino acid substitution of the angiogenesis-related gene hypoxia-inducible factor 2alpha (HIF2A), resulting in weakening of its interaction with prolyl hydroxylase domain-containing protein 2 (PHD2), may increase angiogenesis of BAT. Altogether, our work provides new insights into the molecular mechanisms involved in Arctic adaptation.

Automated summary

This study compared the genomes of muskox and reindeer, and identified common genetic variations related to thermogenesis and circadian rhythm in the Arctic adaptation. It was also found that muskox and reindeer may enhance brown adipose tissue thermogenesis by modulating mitochondrion, lipid metabolism, and angiogenesis pathways. Additionally, an amino acid substitution in the angiogenesis-related gene HIF2A was found to increase angiogenesis of brown adipose tissue. In conclusion, this work provides new insights into the molecular mechanisms involved in Arctic adaptation.