By John Hewitt
One benefit of the closeness between pigs and humans is the potential to be organ donors. There are however, just a few nagging uncertainties that still stand in the way. The big one, the possibility of porcine endogenous retroviruses (PERVs) getting reactivated inside the human organ recipient, is no longer the concern it once was. That comes thanks to the recent groundbreaking work of the one-man army of genetics, George Church, and his lab at Harvard. The latest news, just reported in Nature, is that the group was able to use CRISPR gene-editing techniques to inactivate 62 PERVs in pig embryos.
The one other big concern is rejection of donor organs by the human immune system. Church has reportedly tackled that problem too, by modifying over 20 genes in additional embryos that make the proteins that irritate our immune cells. Although many of these proteins typically reside on the cell surface, they can also be interior proteins which ultimately get chopped up into representative ‘tags’ that are exposed at the surface. We don’t yet know exactly which genes these all are (and they will hopefully soon be published), but one might be able to make a few good guesses.
Researchers in China, have also had recent successes in making multiple CRISPR edits to pig genomes. They were even able to combine the technique with somatic cell nuclear transfer (the method used correct various mutations in the creation of multi-parental embryos) without mosaic mutation or any of the usual undesirable ‘off-target’ effects. Perhaps the most arresting news from the Chinese pig geneticists has been their creation of custom pet rainbow micropigs. Not only are these pigs miniature due to inactivation of one copy of their growth hormone receptor gene, but they can be ordered in different colors.
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