EQUINE SUPERPOWER: What future awaits animals with an edited genome

Photo by Avi Theret on Unsplash

By editing the equine genome, scientists have endowed horses with superpowers. The animals experienced a sharp increase in both body mass and running speed. Yet the news was received ambiguously. Genetically modified breeds are gaining increasing recognition among farmers, and some zoos are also expressing interest. Athletes, however, are categorically opposed. Recently, in particular, genetically modified horses were banned from being used in polo.

CLONING A CHAMPION

ooking at these horses, you would hardly notice anything unusual. And yet there is something extraordinary about them — hidden in their genomes. These horses are the first of their kind to be clones of the prize-winning stallion Polo Purezi. They are an exact copy of the champion in everything except one detail. Their myostatin — a peptide involved in regulating muscle development — has been modified so that their muscles can work at an accelerated rate. To obtain embryos through cloning, researchers used CRISPR, a technology that cuts the genome at a specific point to alter gene expression and achieve the desired trait.

HORSE BREEDERS SOUND THE ALARM

It took employees of the Argentine biotechnology company Kheiron ten months to create five horses with edited genes. The news immediately sparked fierce debate among Argentina’s horse breeders. The reason is simple: polo is extremely popular in this country. It is a team sport in which participants on horseback move a ball across the field using a special mallet. Polo is one of the oldest games on earth, originating — like the tradition of horse breeding — thousands of years before the Common Era. The homeland of polo is considered to be the territory of Persia, where the game was called «chovgan». The first recorded competition dates back to 600 BCE. The sport appeared in its modern form thanks to British colonizers, who adopted it in India.

DOES SPORT NEED CLONES?

Today, polo enthusiasts are sounding the alarm — new biotechnologies threaten centuries-old traditions of selecting and breeding elite horses. Recently, the Argentine Polo Association banned the use of horses with edited genomes in the sport. And the International Federation for Equestrian Sports introduced a similar ban back in 2019. Representatives of the sporting community insist that horse breeding is an art, having nothing in common with the aims of industrial livestock production. Scientists view this process as a science. But evidently, breeding horses has now become both.

HEAT-RESISTANT COWS

The horses produced by Kheiron are not the first animals to have their genomes edited with CRISPR. Such organisms are already a commercial reality — and, unsurprisingly, their primary applications are found in agriculture rather than sport. CRISPR methods are constantly being refined and are gaining increasing acceptance among livestock breeders, who enhance the productivity of their herds by altering their genomes. For example, editing the prolactin receptor gene in PRLR-SLICK cattle made their coats shorter and smoother. As a result, the cows became more resistant to heat stress. This means that the production of meat and dairy products will become more accessible for countries with hot climates. Meat and milk from PRLR-SLICK cattle are not yet available on the open market. But in 2022, the U.S. Food and Drug Administration (FDA) already approved the meat of these cows for production and consumption.

BODYBUILDER SHEEP

This year, Indian scientists announced the first «pumped-up» sheep whose genome was edited using CRISPR. They modified the animals’ myostatin gene — the same one altered in the Argentine horses. As a result, these sheep developed significantly increased muscle mass, as if they had spent years in the gym. Beyond improving meat productivity, there is another major reason scientists clone animals using CRISPR: disease resistance. The British company Genus has created pigs resistant to the virus that causes porcine reproductive and respiratory syndrome, a deadly disease for piglets. In 2020, the FDA approved their sale in the United States, and the animals are expected to enter the market in 2026.

HYPOALLERGENIC PIGS

CRISPR is also widely used to produce animal-derived foods that are safer for human consumption. To obtain hypoallergenic pork, geneticists use CRISPR to inactivate the gene responsible for synthesizing «alpha-gal», a sugar molecule present in most mammals. In some people, consuming red meat containing alpha-gal can trigger allergic reactions. Moreover, gene editing can reduce the risk of organ rejection when pig organs are transplanted into the human body. Corresponding approvals for biomedical use and for consumption were also granted by the FDA in 2020.

ETHICAL ISSUES

The list of animal species edited with CRISPR continues to grow. And with it, the number of ethical questions raised by the public is growing as well. Concerns about traditions disrupted by gene-edited horses are far from the most alarming. There is a possibility that gene editing may have unintended consequences for the health of animals and for the humans who consume them. No one yet knows what negative reactions may arise due to alterations introduced into the genome. Some of them may reveal themselves only over time.

ARE MUTATIONS SAFE?

Side effects may include off-target mutations that can lead to health problems and premature death. Adding to these concerns is the fact that gene edits are inherited and may spread to wild animal populations. Research is needed to track any potential negative consequences of gene editing in animals for human health. Yet it hardly seems that the corporations funding genetic projects are genuinely interested in such studies.

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