BIF 2019: Update on Gene Editing

Alison Van Eenennaam
UC-Davis

United States beef cattle inventory has decreased since the 1970s. However, over that same time period, we have produced more beef. This means we are more efficiently producing more beef per cow. This is very different compared to other countries such as Brazil and India.

We have seen inflection points in the genetic progress of beef production as various technologies have been adopted? Will gene editing be that next inflection point?

Gene editing technologies are simply scissors that cut DNA. There are various types, such as Zinc Finger Nucleases, TALENS, and CRISPR/Cas9. CRISPR has become very popular recently because it uses a guide RNA to make the cut at a specific location. CRISPR can make site-specific variants (mutations) as the cell repairs the double stranded breaks. CRISPR can also be used to insert new sequence from a different animal, species, or kingdom.

There are 13 papers that describe edits for 12 different traits in cattle.

Gene editing for disease resistance is a win-win for cattle sustainability. We produce animals that have better welfare and need to use fewer antibiotics and treatments.

The Polled allele frequency is 0.0071 in Holstein dairy cattle. If used exclusively, polled sires would increase inbreeding and slow genetic gain.

The public generally supports gene editing for animal welfare issues, such as Polled. However, the public does not realize that there are zero gene edited animals currently in the food chain.

Introducing gene edits into an animal can be complicated and cannot slow down a breeding program. We can do that by editing a cell line and cloning that cell line. Or, you can directly edit an embryo, but this embryo  is a mixture of unedited and edited cells. If some of the edited cells are in the germ line, then the animal can pass on the edit to their calves.

Big problem is how gene edits are regulated in plants by the USDA and in animals by the FDA. In plants, if you could have made the change via traditional methods (i.e. cross two lines), then the gene edit is not regulated. The regulations for animals are completely opposite. The FDA is regulating the process of gene editing. Any edit is treated as a new animal drug. Basically, plant breeders can use gene editing and animal breeders can not.

Other countries are taking a much more scientific, risk-based (not processed based) policy. This technology is going to be used in Canada, Argentina, and Brazil. In Australia, the policy doesn't make a lot of sense as non-template edits are not regulated but template-guided edits are regulated. The European Union has said that all mutagenesis processes (if not established before 2001) are regulated. However, if you radiated a plant prior to 2001 and made thousands of mutations, that plant is not regulated.

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