In this file:
· Meet Cosmo, a Bull Calf Designed to Produce 75% Male Offspring Scientists Use CRISPR Technology to Insert Sex-Determining Gene
… Van Eenennaam says part of the motivation to produce more male cattle is that male cattle are about 15 percent more efficient at converting feed into weight gain. They are more fuel-efficient than females. Additionally, they tend to be processed at a heavier weight. It could also be a win for the environment, with fewer cattle needed to produce the same amount of beef…
· The future of beef might be a sausage fest
… On Thursday, Owen, along with, Alison Van Eenennaam, an animal geneticist at U.C. Davis, and a team of seven other scientists, revealed Cosmo’s existence. It’s the first time anyone has produced a bull-calf that could sire 75 percent male calves — rather than the normal 50 percent…
Meet Cosmo, a Bull Calf Designed to Produce 75% Male Offspring Scientists Use CRISPR Technology to Insert Sex-Determining Gene
By Amy Quinton, UC Davis
July 23, 2020
Scientists at the University of California, Davis, have successfully produced a bull calf, named Cosmo, who was genome-edited as an embryo so that he’ll produce more male offspring. The research was presented in a poster today (July 23) at the American Society of Animal Science meeting.
Using the genome-editing technology CRISPR, researchers can make targeted cuts to the genome or insert useful genes, which is called a gene knock-in. In this case, scientists successfully inserted or knocked-in the cattle SRY gene, the gene that is responsible for initiating male development, into a bovine embryo. It’s the first demonstration of a targeted gene knock-in for large sequences of DNA via embryo-mediated genome editing in cattle.
“We anticipate Cosmo’s offspring that inherit this SRY gene will grow and look like males, regardless of whether they inherit a Y chromosome,” said Alison Van Eenennaam, animal geneticist with the UC Davis Department of Animal Science.
More males, more beef
Van Eenennaam says part of the motivation to produce more male cattle is that male cattle are about 15 percent more efficient at converting feed into weight gain. They are more fuel-efficient than females. Additionally, they tend to be processed at a heavier weight.
It could also be a win for the environment, with fewer cattle needed to produce the same amount of beef. “Ranchers could produce some females as replacements and direct a higher proportion of male cattle for market,” said Joey Owen, a postdoctoral researcher in animal science who is leading the project with Van Eenennaam.
An arduous journey
The SRY gene was inserted into bovine chromosome 17, which is a genomic safe harbor site. That ensures the genetic elements function predictably and don’t disrupt the expression or regulation of adjacent genes. Chromosome 17 was chosen after unsuccessful attempts to knock-in the gene on the X chromosome, which would have resulted in a bull that produced only male offspring. Cosmo is expected to produce 75 percent male offspring — the normal 50 percent XY animals, and another 25percent XX animals that inherit the SRY gene.
“It took two and a half years to develop the method to insert a gene into the developing embryo and another two years to successfully establish a pregnancy,” said Owen. But in April of 2020, a healthy 110-pound male calf was born.
“This has been a real labor of love,” said Van Eenennaam.
She said this is just the beginning of the research. Cosmo will reach sexual maturity in a year, and he will be bred to study if inheriting the SRY gene on chromosome 17 is sufficient to trigger the male developmental pathway in XX embryos, and result in offspring that will grow and look like males. As the Food and Drug Administration regulates gene-editing of animals as if they were drugs, Cosmo and his offspring will not enter the food supply.
Other researchers on the team include James Murray, Pablo Ross, Sadie Hennig and Jason Lin with the UC Davis Department of Animal Science, and Bret McNabb and Tamer Mansour of the UC Davis School of Veterinary Medicine.
This project was supported by Biotechnology Risk Assessment Grant Program from the U.S. Department of Agriculture, the California Agricultural Experiment Station at UC Davis and the USDA NIFA National Needs Graduate and Postgraduate Fellowship.
Alison Van Eenennaam, Department of Animal Science, email@example.com
Joey Owen, Department of Animal Science, firstname.lastname@example.org
Amy Quinton, UC Davis News and Media Relations, 530-752-9843, cell 530-601-8077, email@example.com
The future of beef might be a sausage fest
By Nathanael Johnson, Grist
Jul 24, 2020
In April, a little black calf with dabs of white on his back hooves was born. It was the first time Joey Owen, a postdoctoral researcher at the University of California, Davis, had ever seen a cow give birth, and he watched in wonder as the calf, Cosmo, stood up and took its first steps on wobbly legs. Owen had spent the better part of five years working toward this moment, refining the process of gene editing as he collected eggs, fertilized them to create zygotes, and injected genome editing reagents into these one-cell embryos. One of those zygotes became Cosmo.
“It was surreal,” Owen said.
On Thursday, Owen, along with, Alison Van Eenennaam, an animal geneticist at U.C. Davis, and a team of seven other scientists, revealed Cosmo’s existence. It’s the first time anyone has produced a bull-calf that could sire 75 percent male calves — rather than the normal 50 percent. It could also be a win for the environment, with fewer cattle needed to produce the same amount of beef. Bulls have fewer methane belches per hamburger patty. They simply grow more efficiently, requiring less water, less feed, and less land than females to bulk up. “They are more like a Prius than a Hummer,” Van Eenennaam said.
This comes at a time when the livestock industry is searching for ways to fix up its image as a climate villain. Burger King recently tried to do some brand PR with a yodeling kid acknowledging the problem. Ranchers are investigating more climate-friendly management techniques. And big companies are partnering with environmentalists to keep forests from turning into pastureland (with mixed results). But the biggest value in creating Cosmo might be in the breakthrough he represents in the field of gene editing.
Back in 2015, Van Eenennaam asked Owen if he wanted to try his hand at genome editing a bull so all its offspring grew like males. No one had ever done anything like this before, and Owen said he figured the chances of success were slim to none. “OK,” he said, “let’s do it.”
Van Eenennaam planned to take a gene that initiates the development of male physiology from the Y chromosome and add it to the X chromosome. (Reminder: male is XY; female is XX) That way, even genetically female cows with two X chromosomes should develop as males.
The scientists chose a location on the X chromosome that didn’t seem chockablock with important genes, one where they might add a gene without messing anything up. It appeared to be a blank spot on the map of the bovine genome. But it was only blank because it was unexplored: As soon as Owen edited this spot, the embryos died.
After a lot more hard work and experimentation, the scientists discovered the techniques necessary to add a gene to a cow zygote, which might be the most revolutionary element of this research, Owen said. Now other scientists have much better knowledge of hot to add genes to protect animals from getting all sorts of gruesome diseases.
“This opens up the possibility of tackling a lot of issues related to livestock,” he said.
It will also help scientists understand what happens when gene editing gets a little messy. After Cosmo was born, Van Eenennaam took some of the calf’s blood so that he could look closely at the spot where the new gene had entered the DNA. It was in just the right place, but instead of one copy of the gene, there were seven. There was also a bit of DNA wedged in there, left over from the genetic delivery mechanism the scientists had used.
These scrambled genes may conjure images of monstrous mutants, but it’s likely they won’t cause problems. Gene duplication and mixing happens all the time during normal reproduction. And Cosmo seems, well, strong as a bull...