By Ken Fletcher
A GENE editing technique which is being pioneered using pigs, could help to improve stocks of farmed animals by boosting supplies of sperm from prized sires.
Scientists from the University of Edinburgh’s Roslin Institute, Washington State University, the University of Maryland and the US Department of Agriculture’s Animal Bioscience and Biotechnology Laboratory, have worked together on the project to create male pigs that could be used as surrogates capable of producing sperm that contains the genetic blueprint of the most sought-after pigs.
Though the work is primarily with pigs, Roslin's Professor Bruce Whitelaw, the head of developmental biology, said that the technique could be applied to any farm species. This means that gene editing could have massive implications for stud businesses around the globe.
Basically, the surrogates have functional testes but do not have specialised stem cells that are required to produce sperm containing their own genetic information, the researchers said.
Then stem cells from male pigs with desirable characteristics – such as greater resilience to disease, yield and growth – are transplanted into these surrogates to produce limitless supplies of the valuable sperm.
Previous efforts to preserve sperm stem cells from genetically superior pigs by transplanting them into surrogate pigs have so far had limited success, but this new research has changed all that.
Existing methods use chemotherapy drugs or irradiation to remove sperm stem cells from the recipients, before transplanting donor cells. This can also damage other tissues in the testes that are needed for sperm production.
Now, researchers have used a sophisticated genetic tool, called CRISPR/Cas9, to alter individual letters of the pig’s genetic code leading to inactivation of a gene called NANOS2. Scientists found that pigs with two copies of the DNA change did not have sperm stem cells and could not produce sperm, making them completely sterile.
All other aspects of testicular development were completely unaffected and the animals are otherwise healthy. Female pigs were also unaffected by the change to their genetic code.
Pigs with only one copy of the DNA change are still fertile and could be used to produce more of the surrogate animals using conventional breeding techniques, researchers said.
The team says the breakthrough will allow farmers to preserve sperm from prized animals in perpetuity.
Professor Whitelaw said: “This could dramatically improve the production efficiency and quality of farmed pigs, as well as enhancing other desirable traits, such as disease resilience, in production animals.”
* The Roslin Institute received strategic funding from the Biotechnology and Biological Sciences Research Council for the project.