Chicken genome analysis will benefit human health and agriculture

12/06/04

EAST LANSING, Mich. We may soon be thanking Michigan State University chicken No. 256 for better treatments or even new vaccines for the flu and other human ailments.

As the first bird and the first agricultural animal to have its genome sequenced, the chicken is paving the way for research on human diseases, as well as studies on chicken breeding to benefit agriculture. An international consortium of scientists that includes a researcher from Michigan State University analyzed the chicken genome and published a paper in the Dec. 9 issue of the British science journal Nature.

The first draft of the chicken genome was placed into free public databases for use by researchers around the world in March 2004.

The bird whose genome was sequenced, a red jungle fowl (Gallus gallus) known by her wing band number, 256, still lives on the MSU campus in a facility that serves the lab of Jerry Dodgson, professor of microbiology and molecular genetics at MSU, who has worked on mapping the chicken genome for the past 17 years. At 7, she's quite old for a chicken and is oblivious to the importance of her contributions to science.

No. 256 was chosen as the genome model because she's from an inbred line; this makes her genome more uniform than non-inbred chickens. Also, red jungle fowl represents the wild type species from which all domestic chickens came. A female was chosen because female birds contain a sex chromosome (called W) that male birds lack. She also provided DNA used to create recombinant DNA clone maps of the chicken genome. Those maps provided the framework for the much more detailed genome sequence assembly.

"Chickens and humans are, in some cases, infected by the same viruses, bacteria and parasites," said Dodgson, one of the coordinators of the International Chicken Genome Sequencing Consortium, which sequenced and analyzed the red jungle fowl genome. "The research shows that chickens and humans share more than half of their genes. The chicken genome sequence is expected to help us uncover genes that enhance natural disease resistance in birds. Then we can see if those same genes are in humans."

Widely used in biomedical research, the chicken is an important model for vaccine production and the study of embryology and development, as well as for research into the connection between viruses and some types of cancer.

Dodgson, whose research is also funded by the Michigan Agricultural Experiment Station at MSU, said the sequenced genome may someday allow poultry producers to know why certain chickens lay more eggs than others or why certain broiler chickens may have less fat. They then can identify commercial chickens with the same genetic predisposition to these desirable traits.

"If we know the genes that influence these traits, we can select chickens that better meet consumer demand and, at the same time, are healthier, themselves," he said.

"The chicken genome fills a crucial gap in our scientific knowledge," said Francis S. Collins, director of the National Human Genome Research Institute, which is part of the National Institutes of Health, which funded the chicken genome sequencing project. "Located between mammals and fish on the tree of life, the chicken is well positioned to provide us with new insights into genome evolution and human biology. By comparing the genomes of a wide range of animals, we can better understand the structure and function of human genes and, ultimately, develop new strategies to improve human health."

"Having the chicken genome sequenced is a fundamental tool for doing research in chicken genetics," Dodgson explained. "Now, whatever trait we want to look at whether it's resistance to a virus or how the bird responds to a new type of feed we can hone in on the genetic component."

He compared biologists' knowing the genome sequence to a sociologist's wanting to study the population of New York City and using a telephone directory.

"How useful is the phone book for that?" he asked. "It doesn't provide answers on its own, but it does give you a summary of who's there and how to reach them. It's a starting point for asking and answering all the more complex questions. That's what sequencing the genome does for us now we know where all the genes are, and we can analyze them and find out what they do."

Researchers estimate that the chicken has between 20,000 and 23,000 genes in its 1 billion DNA base pairs. The human count is 20,000 to 25,000 genes in 2.8 billion DNA base pairs.

"Genomes of the chicken and other species distant from ourselves have provided us with a powerful tool to resolve key biological processes that have been conserved over millennia," said Richard Wilson, of Washington University School of Medicine in St. Louis, the consortium's leader. "Along with the many similarities between the chicken and human genomes, we discovered some fascinating differences that are shedding new light on what distinguishes birds from mammals."

Like all birds, chickens are thought to have descended from dinosaurs in the middle of the Mesozoic period and have evolved separately from mammals for at least 310 million years. Chickens were first domesticated in Asia, perhaps as early as 8000 B.C.

The consortium was made up of more than 175 scientists from China, Denmark, France, Germany, Japan, Poland, Singapore, Spain, Sweden, Switzerland, the United Kingdom and the United States

Source: Eurekalert & others

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