Bovine genome project could trigger farming revolution

Posted by Emma Woollacott

HOUSTON - She looks a little embarassed by all the attention, and no wonder - Hereford cow Dominette has come under a level of scrutiny that most pop stars would find a bit much.


It's the first time that a cow's genome has been sequenced, and it could lead to a revolution in farming, says the Baylor College of Medicine  Human Genome Sequencing Center, by helping farmers boost milk production and create healthier herds. "The mammals we have looked at previously have been laboratory animals and humans," said Dr. Kim C. Worley, associate professor in the sequencing center and a corresponding author. "This is the first mammalian livestock animal we have studied."


The cattle sequence took six years to complete, annotate and analyze and has involved over 300 scientists from 25 countries. The authors concluded that the bovine genome, consisting of at least 22,000 genes, is more similar to that of humans than that of mice or rats. They note that most cattle chromosomes correspond to part or all of human chromosomes, although the DNA is rearranged in some areas.


"During evolution, domesticated cattle and other ruminants diverged from a common ancestor that gave rise to humans about 95 million years ago, yet cattle and humans still share a high degree of conservation in the organization of their chromosome architectures, far more so than humans and mice do," said Dr. Harris Lewin, one of the lead analysts from the University of Illinois at Urbana-Champaign. "We were surprised to find that, like humans, duplicated segments appear to have played a major role in the rearrangements of chromosomes in the cattle lineage."


The researchers said, "Observation suggests that species-specific changes in genome organization and gene regulation may help tailor the functional components of milk to the specific needs of newborn mammals. They also add to the mounting evidence that milk contains 'innate immune' proteins that may be important for gut protection and gut development in the suckling young as well as the health of the mammary gland."


"More generally, it appears that the cow has significant rearrangements in many of its immune genes and enhanced innate immune defense capacity. This may be in response to increased risk of opportunistic infections at mucosal surfaces caused by the large number of microorganisms carried in the rumen (the largest of the four compartments that make up the bovine stomach)," said Dr. Ross Tellam of the Commonwealth Scientific and Industrial Research Organization of Australia.


The knowledge gleaned from this sequencing could lead to more efficient beef and milk production, the researchers noted.


Dr Gordon Doak, president of the National Association of Animal Breeders, an industry trade group of organizations that market semen for breeding dairy and beef cattle, said, "The availability of very large numbers of single nucleotide polymorphisms [single letter changes in the genetic blueprint] has allowed the development of gene chips that measure genetic variation in cattle populations and will allow the rapid selective breeding of animals with higher value commercial traits. This technology is quickly transforming the dairy genetics industry and has the potential to dramatically alter beef cattle industries as well."


"The future challenge will be to explore the bovine genome sequence in greater depth to fully understand the genetic basis of the evolutionary success of ruminants as this will provide opportunities to address some of the crucial issues of the present time – efficient and sustainable food production for a rapidly increasing human population," said Dr. Richard Gibbs, director of the BCM Human Genome Sequencing Center and principal investigator on the project.


Two reports on the project appear today in the journal Science.