Researchers develop comprehensive genetic map for bison and discover gene responsible for albinism

A research team led by scientists at the Texas A&M School of Veterinary Medicine and Biomedical Sciences (VMBS) has developed the most comprehensive genome ever for the North American bison, updating the animal’s genetic blueprint with the latest genome sequencing technology. . In doing so, the research team also discovered the gene responsible for albinism in bison.

The study – recently published in G3: Genes, Genomes, Genetics—details the development of this high-resolution reference genome, which researchers then used to produce the first test for genetic mutations, starting with the mutation responsible for albinism.

Albinism, a rare condition characterized by a lack of pigment in an animal’s body, making it appear white with red eyes, has historical significance because the albino bison was recognized as a religious symbol for some Native American Indian tribes.

The study also lays the framework for determining other genetic variations that impact important bison traits, such as those that contribute to the health and production value of this species.

James Derr, a professor of veterinary pathobiology and genetics at VMBS who led the research team that created the first bison genome in 2015, brought together the team that developed this new reference genome. This team includes assistant professor of genetics Dr. Brian Davis, graduate student Sam Stroupe, and representatives from Texas Parks and Wildlife and the National Park Service.

“Because reference genomes can help researchers identify and characterize genes responsible for a large number of traits, this technology is used to do all sorts of things, including diagnosing health conditions and developing targeted treatments,” Davis said. .

The newest bison reference genome was developed using technology that allows researchers to create genomes based on the DNA of hybrids, which are animals with DNA from two different species. In this case, the researchers used DNA from a type of bison-cow hybrid called F1, or individuals with a perfect 50-50 split between their parents’ DNA.

In general, F1 hybrids between bison and cattle are rare, but they have happened historically, as we now know that most bison herds in North America contain descendants of bison-cattle hybrids – a finding that Derr and his colleagues research partners did last year.

“One day we got a call from Texas Parks and Wildlife saying they knew someone who had an F1 hybrid,” Derr said. “It was the first fully documented first-generation F1 hybrid I’ve seen in 25 years of working with bison. That’s why we were able to do it.”

To create the new bison genome, researchers first sequenced the genome of the F1 hybrid, as well as that of the bison mother and domestic cattle father. With this information, they were able to separate the bison DNA from the cattle DNA regions in the hybrid.

Because the cattle genome is already very advanced, it provided a reference for creating the new bison genome, helping to guide researchers in developing the high-resolution complete bison reference genome.

To prove the usefulness of the new genome, the team decided to discover the genetic mutation responsible for albinism in bison and create a genetic test that could be used to identify carriers of that mutation.

The discovery is the first time anyone has successfully determined the genetic mutation responsible for an observable trait in bison.

“We knew that albinism was an inherited recessive trait, but we didn’t know which gene was responsible,” Stroupe said. “So we sequenced the DNA of some albino bison and compared them to those with normal coloring to find the mutation that causes albinism. It turns out that the mutation causes an important enzyme to stop working properly, which leads to a lack of pigmentation in the skin.”

The uniqueness of the albino bison

Many North American indigenous peoples regard white bison as sacred entities with prophetic spiritual associations. While not all white bison have albinism, the birth of one is cause for celebration in some communities.

Despite this cultural significance, Derr is not suggesting that people try to breed albino bison using genetic testing.

“Unfortunately, albino bison are often not very healthy,” Derr said. “They tend to develop skin cancer and can develop other health problems as they age.”

The albino bison is also different from the white or brown bison that results from crossing the bison with white cattle, particularly Charolais. These bison do not have the red eyes and pink noses of true albinos.

Now that a more accurate bison genome exists, scientists can learn more about the genetic makeup of the North American bison population.

“The development of this new reference genome and the identification of a causative genetic mutation is exciting news for the bison,” Derr said. “This opens the door to new discoveries and insights into bison genetics.

“Overall, this is a vital step toward future conservation management of the United States’ national mammal,” he said.