Get ready for designer dogs.
Researchers in China have created the first dogs whose DNA was modified by gene editing.
By tweaking a dog’s DNA to cut out a gene for the muscle-limiting protein myostatin, they created a beagle with twice the normal amount of muscle, they reported last week in the Journal of Molecular Cell Biology.
As MIT Technology Review reported, the researchers plan to tweak the DNA of dogs to make them develop diseases similar to Parkinson's and muscular dystrophy, so they can study how these diseases work.
Beagles are commonly used in medical research because they share similarities with humans in their physiology, anatomy, and metabolism, the researchers wrote in the study.
Meet Hercules and 'heaven dog'
A team of researchers led by Liangxue Lai of the Guangzhou Institutes of Biomedicine and Health used an increasingly popular technique known as CRISPR/Cas9, which makes it relatively cheap and easy to cut and paste bits of the natural DNA of any organism. Originally discovered in bacteria, the technique is now used in a wide variety of animals, and has even been used on human embryos.
They edited the DNA of dog embryos to cut out the mystatin gene, which produces a protein (myostatin) that limits muscle formation. The first attempt failed to produce any viable pregnancies. Their second attempt produced 27 puppies, but only one male and one female were found to have two copies of the altered myostatin gene.
They named the female dog Tiangou, after the "heaven dog" in Chinese myth, and the male dog Hercules after the mythical Greek hero, according to the study. The edits didn't completely take effect in Hercules, who still had some cells that produced myostatin. But it worked like a charm in Tiangou, who developed twice the amount of muscle as her littermates, especially on her thighs.
Additional testing showed that the myostatin mutation was present in some of Hercules' sperm, suggesting the change could be passed on to other generations through breeding.
This isn't the first time scientists have tinkered with an animal's DNA to give it more muscle. In June, researchers from South Korea and China created "double-muscled" pigs by tweaking the same gene.
Mutations in the myostatin gene can also happen naturally. A breed of cattle called Belgian Blues normally lack this gene, and grow to massive proportions. The only dogs known to have this mutation naturally are Whippets.
The photos below show dogs with two copies of the natural myostatin gene (column A), and one copy (column B) or two copies (column C) of the mutant gene:
(Mosher DS, Quignon P, Bustamante CD, Sutter NB, Mellersh CS, Parker HG, et al. (2007) A Mutation in the Myostatin Gene Increases Muscle Mass and Enhances Racing Performance in Heterozygote Dogs. PLoS Genet 3(5): e79. doi:10.1371/journal.pgen.0030079)
The team that created the muscly dogs told MIT Technology Review that they don't have any plans to sell the animals as pets, but others have already been moving into this controversial area.
At the end of September, scientists at Chinese genomics institute BGI altered the genes of pigs to sell as pet "micropigs."
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