For decades, researchers have been exploring the possibility of using pig organs in humans, so that a steady supply of organs for transplant could be created. But concerns about infection of human cells caused by viral genes (PERV genes) lurking in the pigs’ DNA have hindered the research progress.
Earlier this month at the National Academy of Sciences in Washington, geneticist George Church of Harvard Medical School announced that he and his colleagues had used the CRISPR/Cas9 gene-editing technology to inactivate 62 porcine endogenous retroviruses (PERVs) in pig embryos. The researchers hope that this achievement may pave way to use pig organs for transplantation into humans.
With the gaining popularity of CRISPR/Cas9 technology which can selectively trim away unwanted genome parts in an efficient manner, Church decided to game on editing the genes with PERVs and make them harmless to pig cells and thus to humans. To eradicate the viruses, he and his team engineered a new set of genes and inserted them into pig embryo cells. The genes produced enzymes that hunted for PERVs and cut out bits of the viral genes. After two weeks, the modified pig embryo cells had altered their own entire viral DNA. The viruses from the pig genome exhibited little activity and the embryo cells grew normally.
A biotech company- eGenesis, founded by Church and his postdoc Luhan Yang to produce pigs for organ transplantation, is now trying to implant the edited pig embryos into mother pigs. This work could lead to PERV-free pigs whose organs would be safe for human transplantation
Another notable success Church and his team achieved was that they altered the 62 genes at once. Jennifer Doudna, a biochemist at University of California, Berkeley, who was one of the inventors of CRISPR/Cas9 technology, is impressed by the number of edited genes. If the work holds up, she says, it could be useful for synthetic biology applications where genes can be switched. It will also be useful for human therapies, adds George Daley, a stem-cell biologist at Harvard Medical School, because many diseases with a genetic component involve more than one gene.