Humanizing Pig CD59 Loci and Control by Endogenous Promoter
Synopsis: Despite nationwide efforts to increase organ donation, the United States continues to suffer from widespread organ scarcity. Recent data provided by the Organ Procurement and Transplantation Network reveal 119,996 patients in need of life-saving organ transplantation in America and that only 24,892 organ transplants were performed between January and October 2016. Because of such organ scarcity, researchers have investigated xenotransplantation, the transplantation of tissues or organs from non-human animals into humans, in hopes of providing patients on the wait with an otherwise unavailable transplant.
Rapid progress in xenotransplantation has been stymied by challenges in breeding organisms with specific mutations of xenoantigen-encoding loci, but the recent development of the CRISPR/Cas9 system allows facile, rapid, and reliable editing of organisms’ genes of interest.
Ultimately, our laboratory seeks to ameliorate the problem of organ scarcity by taking advantage of CRISPR/Cas9-mediated genome editing to generate porcine kidneys compatible with transplant into humans. For example, after deleting two xenoantigen-encoding genes, GGTA1 and B4GALNT2, we have been successful in transplanting a genetically-engineered pig kidney into a rhesus macaque, which survived for 15 months – the longest-surviving kidney xenograft to date. While we continue to diminish graft antigenicity by eliminating specific xenoantigens, we are interested in “humanizing” pig tissue by swapping porcine genes with human homologs using CRISPR/Cas9. Specifically, we will humanize the porcine CD59 locus, which encodes a complement regulatory protein inhibiting formation of the membrane attack complex. We hope to thereby simultaneously delete a potential xenoantigen, more appropriately regulate human complement, and ultimately increase xenograft survival.