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Gene Editing Creates Pigs Resilient to African Virus

Pig close-up

(Mutinka, Pixabay)

23 February 2016. University and industry researchers edited the genomes of domesticated pigs to create a variety better able to withstand a deadly tick-borne virus. The team from University of Edinburgh and the biotechnology companies Sangamo BioSciences and Genus plc published its findings in yesterday’s (22 February) issue of the journal Scientific Reports.

The team led by developmental biologist Bruce Whitelaw in Edinburgh’s Roslin Institute investigated ways of creating a type of pig that could better survive encounters with African swine virus, also known as African swine fever, a contagious tick-borne disease infecting pig herds in Europe, South America, and Caribbean countries, as well as Africa. No treatments or vaccines are available for African swine virus, which causes serious illness in pigs and often kills a majority of infected herds.

While domesticated pigs are susceptible to African swine virus, their cousins in the wild such as warthogs and bush pigs do not become sick, even when infected by the virus. In earlier research, Whitelaw and colleagues traced this resilient capability to the RELA gene in warthogs and bush pigs, which has a different amino acid composition from the RELA gene in domesticated pigs.

To achieve this change in DNA that better protects domesticated pigs, the researchers adapted a genetic editing technology from Sangamo BioSciences in Richmond, California known as  zinc-finger nucleases, where synthetic enzymes modify DNA sequences, including corrections or insertions. These enzymes, with a hydrocarbon and zinc chemistry, branch out in finger-like protrusions that bind with DNA molecules. Sangamo says it engineers the proteins to predictably and consistently bind with longer DNA sequences.

In this study, the researchers used zinc-finger nucleases to create a variation of the RELA gene in domesticated pigs resembling their cousins in the wild, but occupying the same position in pig chromosomes. These collections of DNA variations, called haplotypes, were edited into the chromosomes of 46 pig embryos, which were later born with wild-species haplotypes, instead of the more susceptible domesticated gene sequences.

While these variations require genome editing with human intervention, the authors believe the alterations could have occurred with traditional livestock breeding, but over a much longer period of time. The researchers next intend to field test the resilience of these genome-edited pigs against African swine virus.

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