The pork industry is very familiar with the devastating impact of Porcine Respiratory and Reproductive Syndrome (PRRS) and the significant potential for improving animal welfare that’s possible with PRRS-resistant pigs. PIC has been researching, developing and validating its FDA-approved gene edit for nearly a decade, but for many consumers, gene editing is still a relatively new topic.

We recently sat down with Dr. Alison Van Eenennaam, Extension Specialist: Animal Biotechnology and Genomics at University of California Davis. She was not directly involved in the development of the PRRS-resistant pig but as a Ph.D. geneticist, Dr. Van Eenennaam has extensive experience in animal breeding.

During our discussion, Dr. Van Eenennaam talked about the potential benefits of gene editing, the important difference between gene editing and Genetically Modified Organisms (GMOs) and what she believes the future looks like with innovative technologies like gene editing.

Read more below:

Question: What is your background?

Dr. Van Eenennaam: I am a Professor of Cooperative Extension in Animal Biotechnology and Genomics at UC Davis. I did an agricultural science undergrad in Australia, and then moved to UC Davis to earn my master’s and Ph.D. I have been at UC Davis for 25 years working on genomic selection, genetic engineering and more.  

Question: Overall, what are your thoughts on gene editing?

Dr. Van Eenennaam: I guess as someone that’s worked in the field of genetics for over 30 years, I think gene editing is an exciting development because it allows you a lot more precision in terms of where you’re able to make alterations in the genome.

Question: How does gene editing work?

Dr. Van Eenennaam: What does gene editing really do? Well, it enables you to go in and focus on specific genes in the genome and potentially inactivate them or turn them off so that they don’t produce a protein that creates an otherwise undesirable effect.

So, you can inactivate, for example, a gene that’s the target location for a virus to gain entry. That precision in targeting which specific sequence in the genome that the editor cuts is really what’s powerful about gene editing, and that’s what, as a scientist, I think is most exciting.

Gene editing is a bit like having a molecular pair of scissors. You can target those scissors to a specific sequence or location within the genome of the pig and introduce a cut in the double-stranded DNA helix. As a result, in a very targeted way we are able to turn off or disable a gene, and in this particular case, we’re turning off the gene that makes the receptor to which the PRRS virus binds. Without that receptor, the virus cannot infect the pig anymore, and then the pigs pass that inactivated gene sequence on from generation to generation. All of their descendants will be resistant to the disease.

And it’s that targeting that is unique and different to older styles of genetic work. In the past, with other methods, it wasn’t precisely targeted to a specific sequence or location in the genome like it is with gene editing.

Question: What, in your words, is the difference between Genetically Modified Organisms (GMO) and gene editing?

Dr. Van Eenennaam: Genetically engineered organisms, or what some call GMOs, result from a form of modern molecular biotechnology that has traditionally been used to introduce a transgenic construct, meaning DNA from a different species, into the genome of another species. What you’re trying to do typically is introduce a useful characteristic like insect resistance into a plant, frequently using DNA from another organism. But where that transgenic construct inserts within the genome is random. In other words, you typically can’t predetermine the location of where the transgene inserts itself in the genome. That’s been the process for developing GMOs.

Conversely, with in gene editing, you are using genetic editors (or “scissors”), like CRISPR CAS 9 to make a targeted cut in the DNA to inactivate a gene. In the case of the PRRS-resistant pigs, there’s no transgenic or foreign DNA introduced, so there are no novel proteins being expressed. The editing is being used to just inactivate a targeted gene.

So the main differences between traditional genetic engineering (GMOs) and gene editing are 1) ability for editing to introduce changes at a specific targeted location in the genome, and 2) there is no introduction of foreign, or transgenic, DNA at the target site in the case of the PRRS-resistant pigs. Rather a snippet of DNA is deleted to remove the sequence coding for the receptor to which the PRRS virus binds. Gene editing and GMOs are not the same thing.

Question: What do you see as being the benefits of gene editing?

Dr. Van Eenennaam: The potential of gene editing is very broad. Beyond agriculture, there are human therapeutic uses. For example, to cure sickle cell disease, which has actually been accomplished recently. I think what’s important for gene editing in animal breeding is that we need to actually edit the germ cells – that is, the sperm or the eggs—depending on which sex we’re talking about, so that the trait gets carried from one generation to the next in the same way that I passed blue eyes onto my children. The beauty of genetics is once you’ve made the edit for disease resistance, it will get passed on faithfully from generation to generation, and so no further inputs are required.

You’ve actually got animals that are disease-resistant, and that is amazing. You just have to do a targeted edit at the gene of interest to remove a protein, and that to me is how it integrates with our existing breeding programs. And to me, it’s synergistic, like a cherry on top of the breeding sundae, if you will, rather than a replacement of conventional breeding.

Question: is gene editing a good way to address disease challenges in livestock production?

Dr. Van Eenennaam: You’re asking a geneticist if genetics is a good way to reduce disease? Yes! One-hundred percent! A genetic solution is so much better than having sick animals.

Question: What does the future of gene editing look like?

Dr. Van Eenennaam: Well, I think it will be used to address problems that we’re facing in both agriculture and human medicine. I mean, that’s kind of what scientists do is they try to solve problems with technology.

And so, in this case, we’re talking a disease-resistant pig, but there are other traits like thermo-tolerance that we potentially could target with a technology like this.

So, I think that it’ll be a split between conventional breeding programs, making improvement on complex traits like growth, and gene editing bringing in useful traits that are controlled by one gene. Like in the PRRS-resistant pig, where you knockout this particular piece of DNA and you get a disease resistant pig. Gene editing synergistically complements genetic improvement because it allows you to keep making progress using conventional selection and targeted editing.

Question: What do you wish consumers understood about gene editing?

Dr. Van Eenennaam: That variations in the sequence of DNA are not a food safety hazard. Every meal you have ever eaten is genetically unique. There was a survey where 80% of people said they supported labeling for food containing DNA! But all food that comes from a living organism contains DNA. DNA sequence variation itself is not a food safety hazard. I wish people would be open to consider the potential uses and benefits of this technology, and whether this solution aligns with their values, rather than focusing on unrealized hypothetical hazards.

For example, we are trying to address this horrible disease, PRRS, in pigs. Pigs are dying and that’s bad. What are our options to address this disease challenge? Can we vaccinate? In this case, there isn’t a very effective vaccination for PRRS. So, what other options do we have? Well, you could have a gene-edited pig. Is that better than having them get sick and dying?

Now, I realize I’m a geneticist, but I think that genetic disease resistance is a better way to approach this disease than having sick animals or needing to vaccinate them every year or other non-permanent solutions to this problem.

I have a hard time arguing against disease resistance as a goal because I really do feel it ticks the three pillars of sustainability: It’s better for the animal. It’s better for the farmer and it’s better for the planet. So, given a choice why would you not want a disease resistant pig?

The views, thoughts and opinions expressed in this article are those of Dr. Alison Van Eenennaam and do not necessarily reflect the views, policies or positions of PIC.

Learn more about how gene editing was used to breed PRRS-resistant pigs.