PRRS virus-resistant nucleus herd ready for breeding upon regulatory approval

Feb 19, 2024

CRISPR is king. That’s what Cooperative Extension Professor in Animal Genomics and Biotechnology at UC Davis, Alison Van Eenennaam, and her post-doc, Alba Ledesma, found out when the European Food Safety Authority asked them to do a review of the global research in genome editing of livestock for food and agricultural production.

“About 80% of all of the edits detailed in peer-reviewed research publications were being done using the CRISPR/Cas9 system. Other editing technologies such as zinc-finger nucleases and TALENs, predated CRISPR/Cas9, and comparatively they're more complicated and expensive to use. They do the same thing, make a double-stranded break in the DNA at a targeted location in the genome, but they're more expensive and complicated to use,” Van Eenennaam says. “That's part of the attractiveness and the democratization of genome editing is that with CRISR/Cas9, you just need to order a different CRISPR guide and you can target the Cas9 to cut at a different region in the genome.”

Last week during the 100th Annual USDA Agricultural Outlook Forum, Van Eenennaam shared the data compiled from the 195 peer-reviewed publications, as well as an update on the work Genus plc has done to develop a new generation of CRISPR-edited pigs that are resistant to porcine reproductive and respiratory virus syndrome.

Of the reviewed papers, approximately 30% of them detailed editing in mammalian somatic cell lines, followed by somatic cell nuclear transfer (SCNT) cloning to produce live edited animals. About 61% of the publications outlined approaches where the editing was done in developing embryos. Seventy-five percent of the applications involved gene inactivation, or as Van Eenennaam refers to it, “gene knockouts targeting a gene that when knocked out results in a particular phenotype or characteristic you want.”

Those specific targeted traits included heat stress tolerance, disease resistance, color alterations, hypoallergenic milk, meat or eggs, reproductive, meat quality and animal welfare traits, such as having cows that don’t grow horns or boars that don’t progress through to sexual maturity to avoid the development of boar taint.

“As a breeder, a lot of these are traits are in the normal breeding objective, using conventional selection,” Van Eenennaam says. “So, we haven't radically changed what we're after. We just have a new way to actually introduce some of these characteristics in a very targeted way.”

Sixty percent of the gene editing work has been conducted in mammals with pigs leading the effort. Van Eenennaam says this is partly due to pigs being a litter bearing species, where you get many offspring in each production cycle.

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