It’s been called “a game changer”, “the technology of the future”, and “revolutionary”. It’s also the subject of a massive and bitter patent dispute that grabbed headlines again this week and has cost more than $15 million in legal fees -- so far. Whatever the outcome of the court battle over ownership of CRISPR-Cas9 genome-editing technology, in just under five years it has already changed impossible to possible.
If you’re not familiar with gene editing, it allows a genome to be changed (mutations) to remove, correct, or introduce a particular trait. There are several different techniques to achieve this, but the simplest, most precise and cheapest is CRISPR-Cas9, which uses enzymes to zero in on the desired location, snip the DNA strands and insert or remove the fragment of DNA required. DNA’s natural repair mechanism takes care of the rest. It’s also ridiculously fast, replacing selective breeding and other genetic techniques that used to take years, decades or entire careers.
From a controversy point of view, gene editing has greater advantages over genetic modification, since, rather than mixing the genomes of two different organisms or species in order to attain the desired trait, gene editing as is described here only works with the DNA within the species. (Sorry, Luke Cage, your abalone shell super skin really is science-fiction, not the work of CRISPR science.) The consequence of keeping the tweaks inside the original organisms own DNA also means it’s more likely to receive approval for consumption, as was the case earlier this year with the CRISPR mushroom.
Because it is so fast and inexpensive, it’s accessible to just about any lab and as a result, use of CRISPR has skyrocketed. A good amount of the attention is focused on human health, in the form of modifications to disease-carrying insects such as the mosquito, or the first use of CRISPR in humans to alter a cancer’s ability to modulate the immune response.
But it’s in animal and plant research, where research and testing can proceed with fewer regulatory restrictions that gene-editing is really beginning to show its impact. Here is a short list of the kinds of benefits it could have for livestock, farmers and consumers of livestock products.
1. Disease resilient and antibiotic-free
Creating livestock that is immune, or at least more resistant to sickness and disease is one of the main targets for CRISPR technology, replacing more cumbersome and less precise methods. In pigs, this includes creation of animals that are resistant to porcine reproductive and respiratory syndrome virus (PRRSV) and African swine fever. Foot and mouth disease, which can affect most cloven-hoofed farm animals and hit UK farms extremely hard in 2001, has also been the focus of gene-editing efforts. Similarly, work is underway to modify a gene in dairy cattle in sub-Saharan Africa to make them resistant to the parasite that causes sleeping sickness, which is currently treated by drugs that end up in the food supply. Other research is tackling disease vectors such as ticks and mosquitos to reduce the incidence of illness and need for costly antibiotics.
2. Addressing allergies
Poultry and other birds are more difficult subjects for gene editing due to the protective structure of the egg and the way in which the developing zygote is fused to the surrounding yolk. Disturbing either is not feasible and once hatched, the chick is often past the prime window to introduce genetic modifications. Nevertheless, recent success has been made by targeting the primordial germ cells – those cells that develop into egg and sperm – to remove the gene responsible for producing two known allergens present in egg whites.
World demand for meat products is expected to increase dramatically with the world’s burgeoning population, while farmable land is expected to decrease. One way to address this is to breed animals that produce more meat, grow more rapidly and are more efficient at converting food into protein mass. Cattle, pigs, goats, sheep and salmon have all been targets for such work. Similarly, cashmere goats in China have been edited to produce longer and more luxurious hair to accompany their bulked-up bodies.
4. No cutting or culling required
One of the more well-known examples of gene editing involves the removal of the dominant gene in cattle and sheep, sometimes called the POLLED gene, that produces horns. Polled animals (those without horns) are desired by some farmers as it is deemed to be safer for the animals and their human handlers. A gene-edited polled Holstein cow that was developed in California currently awaits regulatory decisions, the approval of which could save considerable costs and suffering to animals who would otherwise have their horns cut.
Genetic castration and sex selection represent another area of savings to farmers and reduced animal suffering. This involves gene editing to neuter male piglets to save the farmer from having to manually castrate the animals and prevent what’s known as “boar taint” from contaminating the meat. Other strategies are aimed at sex selection in chickens, where males are typically considered waste and in beef cattle, where females do not produce as much meat.
Traits such as heat and drought tolerance that have developed in animals that live in extreme climates such as sub-Saharan Africa have also been selected for gene editing into species that could not normally survive in harsher climates. Such efforts could help reduce the impact of climate change on farming in some areas or enable marginal sections of land to support the more tolerant animals.
While the focus here has been on livestock, agricultural plants have also been the subject of a great deal of gene-editing research. Wheat, corn, soybeans, tobacco, fruits and vegetables are receiving edits to speed up maturation, increase resistances to pests and disease, and produce larger yields in a greater range of soil and climate conditions.
If the approval of the gene-edited mushroom and fast-growing GMO salmon are any indication, farms will soon be seeing changes that could “revolutionize” the industry. That is, so long as the licenses that will need to be paid for the technology once the patent battle is over don’t make the technology cost-prohibitive.
Top: Penn State's CRISPR mushrooms. Yang Lab photo.
Bottom: Gene-edited polled calf, Hannah Smith Walker, Cornell Alliance for Science