First analysis of platypus genome may impact disease prevention

There’s no doubt about it ... the platypus is one odd duck-billed, egg-laying, lactating mammal. With adaptations like webbed feet to fit its aquatic lifestyle and the poison spurs that decorate males, the platypus represents for many a patchwork of evolutionary development. But LSU’s Mark Batzer, along with an international consortium of scientists led by Wes Warren at Washington University in Saint Louis, Mo., has taken this theory to an entirely new level, proving that platypus looks aren’t only skin-deep – their DNA is an equally cobbled-together array of bird, reptile and mammalian lineages. The consortium conducted the first analysis of platypus DNA in what was the largest platypus population genetics study to date.

“Their genomic organization was strange and a little unexpected,” said Batzer, Andrew C. Pereboom Alumni Departmental Professor of Biological Sciences at LSU and one of the principle investigators of the project. “It appeared much more bird- and reptile-like than mammalian, even though it is indeed classified as a mammal. It’s an ancient animal, too, and it has remained relatively primitive and unchanged, both in physical appearance and genetically.”

What does this discovery mean for the public? The very real potential for advances in human disease prevention and a better understanding of mammalian evolution.

“This is a huge genetic step,” said Batzer. “Understanding is key. We’re learning a lot about mammalian gene regulation and immune systems, which has huge implications for disease susceptibility research. We hope to, in time, identify the underlying causes and methods of disease prevention in humans.”

The platypus was chosen as the subject of this study in large part due to its strange appearance, but other selection factors include the species’ endangered status in its only indigenous habitat, Australia. Platypuses are extremely shy by nature and there has been little success in breeding the animals while in captivity. Researchers hope that some of the clues unearthed in platypus DNA might lead to new directions in conservation efforts.

The international effort to decode the platypus genome was an extremely large-scale undertaking, featuring contributions from dozens of prestigious researchers. Batzer and his team at LSU’s Batzer Laboratories – along with Arian Smit from the Institute for Systems Biology in Seattle and David Ray from West Virginia University in Morgantown, W. Va. – developed a very specific aspect of the project – decoding mobile DNA elements, often called “jumping genes” or even “junk DNA.”

“These mobile elements were once thought to be so small that they had no function,” said Batzer. “But, in reality, they cause insertions and deletions, which can lead to genetic diseases in humans as well as the creation of new genes and gene families in the genome, which can lead to genetic disease in humans.” Because of this, understanding the impact of mobile elements on genome structure is paramount to understanding the function of the genome. In the platypus study, Batzer’s group was able to pinpoint specific instances of mobile element insertions within the species and determine the timing of each genetic event.

Batzer and several different international consortia have succeeded in sequencing the genomes of several species in the past, most recently that of the rhesus macaque and the first marsupial, a small, South American opossum species.

“Each one gives us another piece of the puzzle, which brings us that much closer to answering some of the more pressing questions about gene and genome organization and evolution,” Batzer said.

Source: Louisiana State University