Scientists Have Genetically Engineered Dogs To Make Them More Muscly

Beagles (not pictured) were used in this gene-editing study. MaraZe/Shutterstock

First micropigs, now dogs: Scientists in China have used a gene-editing technique to produce the world’s first genetically engineered pooches. Although these two endeavors share scientific roots, with their production aimed at assisting medical research, unlike the teeny tiny pigs, the researchers behind this latest project are not intending to sell their customized animals as pets.

So it probably won’t come as a surprise that the dogs weren’t engineered to be cuter, fluffier or more pocket-sized: they had their DNA tweaked to make them more muscly. The first of many potential edits the team would like to carry out, this was done with the forces in mind.

With greater muscle mass, the dogs “are expected to have a stronger running ability, which is good for hunting, police (military) applications,” researcher Liangxue Lai from the Guangzhou Institutes of Biomedicine and Health told MIT Technology Review. Later on down the line, the scientists would like to manipulate the dog genome in order to mimic human diseases, which could better our understanding and treatment of certain conditions.

“Dogs exhibit close similarities to humans in terms of metabolic, physiological, and anatomical characteristics,” the researchers write in the Journal of Molecular Cell Biology, “and thus are ideal genetic and clinical models to study human diseases.”

The term “gene-editing” may ring alarm bells in many, but the technique used – CRISPR-Cas9 – is remarkably precise, cheap and efficient, and it’s already widely used in scientific research. Derived from bacteria, the system uses a guide to direct an enzyme – Cas9 – toward a target sequence of DNA before the desired edit is made, whether that be inserting a sequence or disrupting the DNA in some other way.

In this case, the scientists used CRISPR to snip out a gene called myostatin in beagles, the most commonly used dog in biomedical research. Perhaps to the dismay of bodybuilders, the myostatin protein functions to limit muscle growth so that they don’t become too large (yes, there is such a thing). In many species, including dogs, this gene can undergo spontaneous mutation and result in significantly increased muscle mass and strength, without serious negative effects on the animals.

After injecting 35 beagle embryos with their designer CRISPR, the scientists inserted them into female dogs and allowed them to develop. Eight out of 10 females became pregnant, producing 27 puppies, two of which were found to have the desired “knock-out” mutation, later named Hercules and Tiangou. But the dogs didn’t quite become the ultra-buff beagles you may have pictured: Hercules still managed to produce myostatin in small amounts, but significant enough to make him indistinguishable from littermates. Tiangou, however, was noticeably more muscular, showing beefed-up thighs.

While this work was done with a more noble cause in mind, aiding scientific research, the authors do note in the paper that the technique could also be used to create dogs with favorable traits for other purposes, although this doesn’t necessarily mean pets. The ethics of creating designer companion dogs could be argued, but it’s not really that different to what humans have been doing with the species for thousands of years anyway, albeit this method significantly cuts corners.

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