Genetically Edited Hercules Dogs Can Pack on Extra Muscles

Scientists use a natural mutation that produces extra muscle to tweak dogs genes

Robert Dowling/CORBIS

From the country that brought you genetically altered micropigs, comes another announcement that pushes the limits of gene editing. A Chinese team from Guangzhou Institutes of Biomedicine and Health recently presented the world with a pair of super-muscled beagles: Hercules and Tiangou.

Already other research groups have tweaked the genes of monkeys, goats, rabbits and even human embryonic cells using a relatively new technology called CRISPR—a system that uses enzymes to cut and paste select segments of DNA.

Using this method, researchers disabled the gene that codes for myostatin, a protein produced by muscle cells that actually blocks muscle growth. This mutation has cropped up on its own, without scientists wielding gene editing tools, in the beef cattle breed Belgian Blue, racing whippets and humans.

The team injected the gene editor system into 35 beagle embryos. Of the 27 puppies born, only two had the edited genes. Hercules has the mutation in most, but not all of his cells. Yet at four months, the changes were most evident in Tiangou—named for a mythological dog from Chinese legend that eats the sun during an eclipse—who sported more muscular thighs than her unedited sister, reports Tina Hesman Saey for Science News. But now at 14 months, both pups have packed on muscle.

The beagles have "more muscles and are expected to have stronger running ability, which is good for hunting, police (military) applications," one of the researchers Liangxue Lai tells Antonio Regalado of Technology Review. But the ultimate goal of this work is to raise animals with genetic alterations that mimic human diseases like Parkinson's, George Dvorsky reports for Gizmodo. Lai and colleagues published their work earlier this month in the Journal of Molecular and Cell Biology.

They don’t plan to create specialized pets, but that doesn’t mean other groups won’t try, reports Regalado for Technology Review. Given that another Chinese research group is selling genetically edited mini pigs, pets wouldn't be out of the realm of possibility.

While, the micropigs’ genes were tweaked using a different kind of gene editing enzyme, the CRISPR system is considered more powerful and precise. That means even more possibilities. Regalado writes:

[A]t least some researchers think that gene-edited dogs could put a furry, friendly face on the technology. In an interview this month, George Church, a professor at Harvard University who leads a large effort to employ CRISPR editing, said he thinks it will be possible to augment dogs by using DNA edits to make them live longer or simply make them smarter.

The low rate of success for the dogs (two out of 27 puppies) shows that the technology has a ways to go before designer pets are readily available. But the debate is already boiling over the ethics of such gene editing. And as the technology improves, that debate will only intensify.

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