For the first time, researchers have created pigs, goats and cattle that can serve as viable “surrogate fires”
The advance, published in Proceedings of the National Academy of Sciences on 14 September could accelerate the spread of desirable traits in livestock and improve food production for a growing global population. It would also allow breeders in remote regions better access to genetic material from elite animals from other parts of the world and allow more precision breeding in animals such as goats where artificial insemination is difficult to use.
“With this technology, we can better communicate desirable traits and improve the efficiency of food production. This can have a major impact on tackling food insecurity around the world,” said Jon Oatley, a reproductive biologist with WSU’s College of Veterinary Medicine. “If we can tackle this genetically, it means less water, less feed and fewer antibiotics we need to put in the animals.”
A research team led by Oatley used the gene editing tool, CRISPR-Cas9, to knock out a gene specifically for male fertility in the animal embryos that would be raised to become surrogate fathers. The mandibles were then born sterile, but began producing sperm after researchers transplanted stem cells from donor animals into their testicles. The sperm cells produced by the surrogate guys contained only the genetic material from the selected donor animals. The gene editing process used in this study seeks to create changes within an animal species that can occur naturally, such as infertility.
The study is the result of six years of collaboration between researchers at WSU, Utah State University, the University of Maryland and the Roslin Institute at the University of Edinburgh in the UK
The researchers used CRISPR-Cas9 to produce mice, pigs, goats and cattle that lacked a gene called NANOS2, which is specific for male fertility. The mandibles grew up sterile but otherwise healthy, so when they received transplanted sperm-producing stem cells from other animals, they began producing sperm derived from the donor’s cells.
It was confirmed that the surrogate acids had active donor sperm. The surrogate mice became the father of healthy offspring that carried the genes from the donor mice. The larger animals have not yet been bred. Oatley’s laboratory refines the stem cell transplantation process before taking the next step.
This study provides strong evidence for the concept, said Professor Bruce Whitelaw of the Roslin Institute.
“This shows the world that this technology is real. It can be used,” Whitelaw said. “We now need to go in and figure out how we can best use it productively to feed our growing population.”
Latest steps in animal husbandry
Researchers have been looking for a way to create surrogate fathers for decades to overcome the limitations of selective breeding and artificial insemination, tools that either require the presence of animals or strict control over their movement – and in many cases both.
Artificial insemination is common in dairy cattle, which is often restricted, so their reproductive behavior is relatively easy to control, but the procedure is rarely used with beef cattle that need to roam freely to feed. For pigs, the procedure still requires the animals to be nearby, as pig semen does not survive freezing well. In goats, artificial insemination is quite challenging and may require a surgical procedure.
Surrogate father technology could solve these problems, as the surrogates deliver donor genetic material in the natural way – through normal reproduction. This allows ranchers and shepherds to let their animals interact normally in the field or in the field. Donors and surrogates do not have to be close to each other, as either frozen donor sperm or the surrogate animal itself can be sent to different locations. In addition, female NANOS2 knockout animals remain fertile – as the gene only affects male fertility – and could be bred to efficiently generate sterile males to be used as a surrogate father.
This technology has great potential to help food supply places in developing countries where shepherds still rely on selective breeding to improve their population, said Irina Polejaeva, a professor at Utah State University.
“Goats are the leading source of protein in many developing countries,” said Polejaeva. “This technology can enable faster transmission of specific traits in goats, whether it is disease resistance, greater heat tolerance or better meat quality.”
Surrogate-men technology could also open up a new possibility for genetic conservation of endangered species, whose declining numbers leave animal communities isolated from each other and limit their genetic diversity.
Perception and political obstacles
However, none of the benefits of surrogate families can be realized without changes in the current landscape of state rules and public perception.
Even when the technology is advanced enough for commercialization, genetically modified surrogate fathers could not be used in the food chain anywhere in the world under current rules, even if their offspring would not be genetically modified. This is due in part to the misconceptions that gene editing is the same as the controversial gene manipulation, Oatley said. Genetic editing involves changes in a species that can occur naturally. It does not combine DNA from different species.
Oatley realizes that there is a lot of work to be done outside the laboratory and recently joined the National Task Force on Gen Editing in Livestock to bring together researchers, industry representatives, bioethicists and politicians to find a way forward for the technology.
“Even if all science is done, the rate at which this can be translated into action in livestock production around the world will be affected by societal acceptance and federal policy,” Oatley said. “By working with politicians and the public, we can help provide information that assures the public that this science does not carry the risks that other methods do.”
The progress of the pig genes could increase the sperm populations of precious animals
Michela Ciccarelli et al., “Donor-derived spermatogenesis after stem cell transplantation in sterile NANOS2 knockout males,” PNAS (2020). www.pnas.org/cgi/doi/10.1073/pnas.2010102117
Provided by Washington State University
Citation: Genetically edited livestock ‘surrogate sires’ was successfully made fertile (2020, 14 September) retrieved 14 September 2020 from https://phys.org/news/2020-09-gene-edited-livestock-surrogate-sires-successfully .html
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