The platypus (Ornithorhynchus) is a monotreme and is important to evolutionary studies because scientists know that monotremes split from mammalian evolution right before the X and Y sex chromosomes emerged. New genomic research shows their brains have a specific gene linked to exploratory foraging.
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SYDNEY: Mapping the entire set of genes in mammal tissues in 10 species has disclosed for the first time the subtle ways evolution plays out in mammals.
For instance, researchers found the platypus, which has an active foraging behaviour, has a gene important for exploratory behaviour that’s strongly expressed in the brain.
The research provides a basis for understanding organ function in different species that was previously unavailable. This could help future research explain species-relevant gene adaptations.
“This research is important because for the first time we are looking at a vast number of genes in multiple species and multiple tissues,” said geneticist Frank Grützner from the University of Adelaide, who was involved in the Nature study, published last week.
Behind-the-scenes of the entire genome
Many genomic sequencing projects have cropped up over the past 20 years, such as the Human Genome Project and less widely-known, the Platypus Genome Project.
But the evolution of genes mapped on such a species-encompassing scale or in relation to this many tissues has proved impossible until now because of the limits of genome sequencing techniques.
A team led by Henrik Kaessmann from the University of Lausanne in Switzerland investigated all of the genes in organs such as the testes, liver, heart and brain in different mammals including mice, chickens, humans, chimps and platypuses.
They obtained genetic data from six tissues per mammal and improved existing genetic technology before comparing the ways that gene expression evolves in both species and organs.
“In some tissues more changes have occurred than in others. For example, in the brain we observed fewer changes compared to the testes, suggesting that genes in the brain can afford only very subtle changes,” Grützner said.
These findings could shed new light on the biological priorities of species, since the testes are under more evolutionary pressure than the brain.
The big question
“We have seen many genome sequencing projects over the past decade but until now nobody has tackled the big question of how the regulation of genes has changed during 200 million years of mammalian evolution,” Dr. Grützner said.
Grützner explained that one gene, when removed from a mouse brain, showed changes in the mouse’s explorative behaviour.
“I was thrilled with the fact that a gene that is important for explorative behaviour shows high expression in the platypus brain, and I don’t know if you’ve ever seen a platypus in the wild or at the zoo, but the platypus is a highly active forager,” Grützner said.
The platypus (Ornithorhynchus) is a monotreme and is important to evolutionary studies because scientists know that monotremes split from mammalian evolution right before the X and Y sex chromosomes emerged.
Because of its bizarre traits, the duck-billed, egg-laying creature is crucial to our further understanding of how genes have changed after they initiated themselves onto an X or Y chromosome.
Bioinformatics expert Tony Papenfuss at the Walter and Eliza Hall
Institute of Medical Research in Melbourne, Australia, who was not
involved in the study, hopes their data will be quickly integrated into
genome databases. “What this tells us about genes and their expression and
how they evolve will be incredibly useful.”
