Gene-editing: a promising future in dairy

 By Jaclyn Krymowski for American Dairymen

Of all the exciting recent genetic innovations, among the most anticipated is the use of gene editing. This technology can bring desired novel traits to herds and breeds much faster than using generations of selective breeding with all the trial and error that accompanies it. Recombinetics is one company that is leading the way in the development and application of this practice.
Gene-editing is a technology where specifically designed molecular scissors can cause a double strand break at any desired spot on a genome to induce a change. Naturally, the cell can repair the break itself. But when provided with an instruction template to copy, the cell will specifically repair to produce the desired outcome – such as introducing the polled allele. This method of gene editing uses something called HDR or homology direct repair, explains Tad Sonstegard, Chief Scientific Officer of Acceligen – the division of Recombinetics that works on developing genetic technology in various livestock species. Sonstegard, a former research geneticist with the USDA, works on the research and development of gene-editing for Recombinetics.

Application & opportunity
Currently there are two ways this technology is applied to cattle. One is by using the cells harvested from an animal that can be used for cloning, this is the same method that was used to produce Dolly the sheep. The other more common one is using scissors in a single-celled zygote utilizing the IVF procedure. “Once that fertilization happens we can inject the editing mix into the single celled zygote and cause the double stranded break and repair to introduce the allele,” says Sonstegard. This simple process should have no effect on the typical IVF procedure or its fertility outcome.
The near-term future opportunities for this technology are immense and the surface is just being scratched. A big goal at the forefront of this effort is to eliminate the stressful procedure of traditional dehorning. This can be done by introducing the polled allele to more and more of the industry’s elite sires. With gene-editing, the allele can be added without years of breeding or impacting any other traits. “We were very deliberate as far as what we want to work on,” says Tom Erdmann, general manager of Acceligen. “As you can imagine if you look at all the genetic opportunities there are in any animal whether that’s a dairy cow or anything else there are a lot of things you could do, but there’s probably only a few things that you should do. At this point in the life cycle of this technology and in (regards to) government regulatory acceptance and consumer acceptance, we deliberately looked at animal well-being as a really great place to start.”
Other kinds of wellness traits, namely disease resistance and heat tolerance, are perfect examples that improve animal welfare and production efficiency. Tuberculosis, BVD, foot and mouth disease and even tick resistance traits are all carried in individual animals in different breeds. They can all be easily applied using the same HDR method as done with the polled allele once we know their source code at the genomic level. The trait for heat tolerance, once confined to specific breeds, can be used to adapt any breed to perform in the tropics. The widespread implementation of certain traits is especially important on a global scale, says Sonstegard.

Where to go from here
In 2015 the first gene-edited polled Holsteins were born a success. Sonstegard says they are ready to produce commercial animals now, the last hurdle they are waiting on is regulatory approval for their human consumption. Regulations can be tricky from country to country, he says, as there is currently no universal consensus on the marketing of these animals.
From a scientific stand point, these animals are absolutely safe and effective. “There’s no difference between a genetically dehorned animal and a polled bred animal relative to its genome,” says Sonstegard. It is important to note that every trait being introduced through gene editing is already a natural occurrence somewhere within the species. “These are not GMO animals,” says Erdmann. Rather, the goal is to use these available traits to get a desired outcome without going through the time of generations of breeding.
The response from the industry on this technology have been extremely positive. Erdmann says they have garnered solid support from all corners of the industry. Unlike some technological advancements in the industry, gene-editing isn’t one that needs convincing to be adapted. The word from many enthusiastic breeders is that they are wanting to use edited animals as soon as possible.
“We’ve talked to all the different groups, including most breed associations,” says Sonstegard. “They’re willing to work with us and our technology to make sure that animals are tracked appropriately and marketed according to these added value traits that are being brought in through this technology.”