Dr. Alison L. Van Eenennaam is a Cooperative Extension Specialist in the Department of Animal Science at the University of California, Davis and runs the Animal Genomics and Biotechnology Laboratory. She recently spoke about gene editing at K-State’s Cattlemen’s Day. Senior Farm and Ranch Broadcaster Ron Hays is featuring comments from her conversation with K-State’s radio network after her presentation.
Dr. Van Eenennaam explained gene editing as altering the DNA within an animal rather than introducing transgenic DNA. “You are, maybe, inactivating a gene that makes an animal susceptible to a disease,” she detailed. “That is an example being put through the regulatory process at the moment.”
She described pigs resistant to Porcine Reproductive and Respiratory Syndrome (PRRS) as no longer having the protein that the virus binds to in order to infect the pig.
Alternately, adding genes can be equally beneficial. She described replacing alleles, or gene variants from one breed to another. For example, introducing the polled gene from Angus cattle to horned Holsteins without crossing the two breeds or diminishing the Holstein’s strength as a dairy animal.
“That would be when you introduce an allele that is already in your species, so its not transgenic, but it adds value to, for example, Holsteins, because, now, as a dominant trait, none of their calves would have to be dehorned,” Dr. Van Eenennaam revealed.
Collaborating with other companies, the U.C. Davis team has worked on several projects including a knock-out growth trait in sheep, and surrogate sire bulls which she elaborated upon:
“That is a concept where potentially, you could have for example, a tropically adapted bull working in an environment where he is well suited, but you would like, ideally, for his semen to be coming from Angus, so you can basically do A.I. on legs, because you could naturally service with elite germplasm using that technology,” Dr. Van Eenennaam described. “There are a lot of applications where you could potentially add some real benefits to the beef industry.”
She said that there are two basic methods to ensuring that the gene edits are reproduced in an animal’s offspring. “You can take a cell line of an existing animal that is the best bull you’ve ever had, but you’d also like him to have a disease-resistant trait, so you could edit in that cell line, then you could clone it – like Dolly cloning – then basically, you get the same bull, but with the edit. So that is one way to do it,” she described.
“The other way is to basically edit the next generation, so you would go in just after the sperm has fertilized the egg – that is called a zygote. You would introduce the editing reagents to that one-cell zygote and hopefully, you will get both mom and dad alleles changed to whatever you are trying to edit them to. Then that cell will start to divide and become an embryo and ultimately, a cow that would have the edits in it there. Those are the two major approaches,” she concluded.
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