Scientists in China say they are the first to use gene editing to produce customized dogs. They created a beagle with double the amount of muscle mass by deleting a gene called myostatin.
The dogs have “more muscles and are expected to have stronger running ability, which is good for hunting, police (military) applications,” Liangxue Lai, a researcher with the Key Laboratory of Regenerative Biology at the Guangzhou Institutes of Biomedicine and Health, said in an e-mail.
The myostatin gene is well-studied—and because double-muscling isn’t known to have obvious drawbacks—it is frequently cited in debates over hypothetical future “gene-doping” among athletes. U.S. doctors are already attempting to block myostatin in gene-therapy experiments that seek to slow muscle loss in boys suffering from Duchenne muscular dystrophy.
Lai said his group had no plans breed to breed the extra-muscular beagles as pets. Other teams, however, could move quickly to commercialize gene-altered dogs, potentially editing their DNA to change their size, enhance their intelligence, or correct genetic illnesses. A different Chinese Institute, BGI, said in September it had begun selling miniature pigs, created via gene editing, for $1,600 each as novelty pets.
The list of animals already engineered using gene editing in China includes goats, rabbits, rats, and monkeys.
Clearly there is also technical the feasibility of germ line engineering in humans. Human babies could have hundreds of genetic edits for greater strength and intelligence.
The dog researchers took much the same approach, directly introducing the gene-editing chemicals—a DNA snipping enzyme, Cas9, and a guide molecule that zeroes in to a particular stretch of DNA—into more than 60 dog embryos. Their objective was to damage, or knock out, both copies of the myostatin gene so that the beagles’ bodies would not produce any of the muscle-inhibiting protein that the gene manufactures.
In the end, of 65 embryos they edited, 27 puppies were born, but only two, a female and a male, had disruptions in both copies of the myostatin gene. They named the female Tiangou, after the “heaven dog” in Chinese myth. They named the male Hercules.
Lai and his colleagues reported that in Hercules, the gene editing was incomplete, and that a percentage of the dog’s muscle cells were still producing myostatin. But in Tiangou, the disruption of myostatin was complete and the beagle “displayed obvious muscular phenotype,” or characteristics. For example, her thigh muscles were large compared to those of her littermates.
In the USA 60 genes modified at one time in single animals and on the path to large scale edits of genomes
Harvard Professor George Church and his company eGensisis have modified more than 60 genes in pig embryos — ten times more than have been edited in any other animal — researchers believe they may have produced a suitable non-human organ donor.
Geneticist George Church of Harvard Medical School in Boston, Massachusetts, announced that he and colleagues had used the CRISPR/Cas9 gene-editing technology to inactivate 62 porcine endogenous retroviruses (PERVs) in pig embryos. These viruses are embedded in all pigs’ genomes and cannot be treated or neutralized. It is feared that they could cause disease in human transplant recipients.
Pigs with more human like organs for xenotransplants
Church’s group also modified more than 20 genes in a separate set of pig embryos, including genes that encode proteins that sit on the surface of pig cells and are known to trigger a human immune response or cause blood clotting. Church declined to reveal the exact genes, however, because the work is as yet unpublished. Eventually, pigs intended for organ transplants would need both these modifications and the PERV deletions.
Preparing for implantation
“This is something I’ve been wanting to do for almost a decade,” Church says. A biotech company that he co-founded to produce pigs for organ transplantation, eGenesis in Boston, is now trying to make the process as cheap as possible.
Church released few details about how his team managed to remove so many pig genes. But he says that both sets of edited pig embryos are almost ready to implant into mother pigs. eGenesis has procured a facility at Harvard Medical School where the pigs will be implanted and raised in isolation from pathogens.