Thursday, March 9, 2017

Scientists Breed Pigs with Life-Saving Gene Alteration

Piglets are the main focus for PRRS prevention.

Great leaps have been made in research of the pig farming industry as scientists at University of Edinburgh have managed to use gene-editing techniques to halt the infection of one of pig-farmers' worst enemies: Porcine Reproductive and Respiratory Syndrome. Porcine Reproductive and Respiratory Syndrome (PRRS) is a costly and deadly disease that plagues the domesticated pig population with high death rates for both pregnant sows, their fetuses, and young piglets. The virus can cause abortion and mummification of fetuses, as well as severe respiratory issues and extreme weight loss, which causes a large percentage of the piglet population to die before reaching adulthood. This article summarizes the discoveries and the mechanisms behind them.

The pathway for the PRRS virus has now been linked to a scavenger receptor on macrophages known as CD163, a receptor also responsible for managing inflammation and removing hemoglobin. Scientists have managed to pinpoint CD163 as the infection site for PRRS, but due to the other important contributions of CD163, they could not delete the receptor as a whole. However, in the originally published journal detailing the research, the structure of CD163 is described as "pearls-on-a-string", with nine scavenger receptor crysteine-rich domains (SRCR), and from this, the team of Edinburgh managed to pinpoint SRCR5, the domain responsible for the infection of pigs with PRRS.

Using gene-editing technologies, researchers injected 24-39 zygotes with the SRCR5 deleted genes and ended up with 32 live piglets. From this, they took the two pigs that showed the desired deletion of the exon 7 (which is linked to SRCR5), crossed them, and resulted in a mixture of different genotypes, all of which had deletion of exon 7 in varying forms. Exposing these individuals to the PRRS virus did not result in infection, while still maintaining normal functions within the CD163 scavenger receptor. From this experiment, not only did the team at Edinburgh prove that the deletion of SRCR5 can prevent infection of one of the deadliest viruses in domestic pigs, but also that it can be safely and successfully passed on to other generations.

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