The New Era of Beef Begins with ‘Cosmo’ – Gene-Edited Bull

Bull grazing on the fields
Image from Pixabay

Gene-edited bull – a little black calf with white dabs on his back hooves was born in April. Joey Owen, a postdoctoral researcher at the University of California (U.C), had spent the previous five years trying to perfect the process of gene editing by collecting eggs and fertilising them to make zygotes, and injecting the genome editing agents into those one-celled embryos. Cosmo, a gene-edited bull was born from one of those zygotes.

Cosmo’s birth was announced by Owen and Alison Van Eenennaam, an animal geneticist at U.C. and a team of seven other scientists. It’s the first time a bull-calf has been created that can sire 75 percent male calves instead of the usual 50 percent. The main benefit of this new breed is, they require very less amount of cattle and water compared to the normal breed bulls and still they can achieve more size (bulk muscles) and strength compared to the normal ones, also they are highly immune to diseases which is an added advantage.

Gene-edited bull - Cosmo, with the team
Newborn Cosmo with the team, including Joey Owen on left & Van Eenennaam on the right side, Image source: U.C., Davis

The introduction of Cosmo was at the time when the livestock industry was facing a crisis of climate problems caused by cattle feeding. In addition, large corporations are collaborating with environmentalists to prevent forests from being pastureland (with mixed results). Cosmo’s greatest importance, however, may lie in the advancement he represents in the field of gene editing.

How did they do it?

Van Eenennaam intended to transfer a gene from the Y chromosome that initiates the production of male physiology to the X chromosome. (As a reminder, males are XY and females are XX.) This ensured that the offspring of these gene-edited bulls reproduced 75% of their offspring as males (bulls) rather than 50% of males and 50% of females as in normal scenarios.

The researchers selected a spot on the X chromosome that didn’t appear to be overrun with essential genes, allowing them to add a gene without causing havoc. On the map of the bovine genome, it seemed to be a blank space. However, it was just vacant since it had never been explored: The embryos died as soon as Owen finished editing this place.

The experiment helped many scientists to discover the right methods needed to inject a gene to a cow zygote, which was also the greatest achievement of this study. Other scientists now have a much greater understanding of how to add genes to protect animals from a variety of heinous diseases. This study also helped in understanding the consequences of gene editing gone wrong.

Van Eenennaam took some of Cosmo’s blood after he was born so he could examine the place where the new gene had joined the DNA. It was in the right spot, but there were seven copies of the gene instead of one. There was also a tiny bit of DNA in there, leftover from the scientists’ genetic delivery mechanism.

These jumbled genes can conjure up visions of monstrous mutants, but they’re unlikely to cause any problems. During normal reproduction, gene replication and mixing occurs frequently. Cosmo, on the other hand, seems to be as powerful as a bull.

“Cosmo, on the other hand, is not to be eaten. He’s not a steak; he’s a science experiment,” says Vann Eenennaam

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