Duck-billed platypus genome sequence published

Animal's reptilian-mammalian mix reflected in its DNA

The first analysis of the genome sequence of the duck-billed platypus was published today by an international team of scientists, revealing clues about how genomes were organized during the early evolution of mammals. The research was supported in part by the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health (NIH).

Fans of TV nature shows will remember that the duck-billed platypus, native to Australia, is one of the few mammals that lays eggs. However, platypus peculiarity does not end there. For example, these odd animals boast what looks like a duck’s bill, which houses an electrosensory system used when foraging for food underwater, along with thick fur coats adapted for the icy waters in which it resides. Males also possess hind leg spurs that can deliver venom powerful enough to wound territorial competitors during mating season or cause excruciating pain in other mammals, including humans.

“At first glance, the platypus appears as if it was the result of an evolutionary accident. But as weird as this animal looks, its genome sequence is priceless for understanding how fundamental mammalian biological processes have evolved,” said Francis S. Collins, M.D., Ph.D., director of NHGRI. “Comparisons of the platypus genome to those of other mammals will provide new insights into the history, structure and function of our own genome.”

In a paper published in today’s issue of the journal Nature, researchers analyzed a high-quality draft genome sequence of Glennie, a female platypus from Australia. The consortium included scientists from the United States, Australia, England, Germany, Israel, Japan, New Zealand and Spain. Sequencing of the platypus genome was led by the Genome Sequencing Center at Washington University School of Medicine in St. Louis, a part of NHGRI’s Large-Scale Sequencing Research Network.

Once the sequence was produced, researchers began comparing the genome of the platypus, whose ancestors split from the rest of mammalian lineage some 166 million years ago, with the well-characterized genomes of the human, mouse, dog, opossum and chicken, as well as the draft genome sequence of the green anole lizard. The chicken genome was chosen because it is descended from the ancestral group of egg-laying animals, including extinct reptiles, which passed on much of their DNA to animals like the platypus. Scientists were particularly interested in finding features within the platypus genome that could explain the odd mix of characteristics seen in the platypus, those that were more like reptile and birds and which were like mammals.