Gene editing to enhance production in developing nations

Sterile male and female chicken eggs have been implanted with reproductive cells from donor birds with the resulting chickens mated together to produce chicks of the donor breed. The chicks showed characteristics inherited from their real patents, the donor birds, along with the edited change to their DNA, rather than their surrogate parents. The gene editing outcome demonstrates an efficient way to introduce beneficial characteristics, the scientists claim, such as tolerance for warm climates or disease resistance.

Beneficial genes can be transferred from one breed into another via gene editing of embryos, in a single generation, and the method to control the reproductive genes can be carried by both parents – known as Sire Dam Surrogate (SDS) mating – can ensure that offspring will inherit a desired gene from both parents, and exhibit the characteristic associated with that gene. Commercial partner Cobb-Europe worked with a team from the Centre for Tropical Livestock Genetics and Health and the Roslin Institute to demonstrate their approach by using sterile male and female chickens, known as empty nest chickens, to transfer feather characteristics between breeds.

They removed reproductive stem cells (i.e. early stage cells that later develop into sperm and eggs) from chicken embryos using gene-editing technology, and used the same technology to introduce gene-edits into these reproductive cells from another breed. The altered reproductive cells were then implanted into surrogate parents – the embryos of chicks and cockerels that were bred to be sterile. These surrogates were then hatched and mated with one another. Resulting offspring were of the donor breed and not that of their surrogate parents. They also had the new traits created by the gene-editing.

Results

Researchers demonstrated their approach by repairing a natural generic change that causes distinctive white plumage in the White Leghorn breed. Chicks born to the sterile chickens now had a black plumage. Similarly, the team introduced a distinctive curly feather, which is believed to help Western African breeds cope with hot climates, into chicks bred from Light Sussex chickens – a British breed. The concept could allow the transfer of useful traits among the world’s 1,600 chicken breeds and could boost animal productivity and welfare as well as safeguarding against changing environmental conditions.

Comments

Welcoming the developments, Professor Appolinaire Dijkeng, director of the Centre for Tropical Livestock Genetics and Health, said: “Poultry is a key livestock animal for millions of smallholder farmers in low- and middle- income countries. Any gains in efficiency, productivity and health from introducing useful traits from other poultry breeds could significantly improve the lives of these farming families through increased food production and income.”

Dr. Mike McGrew, one of the scientists who worked on the study, said: “The SDS technique is being used now to test genetic variants present in different breeds of chicken and to improve our ability to ‘biobank’ breeds of chicken. Genome-edited chickens are not allowed in the food chain. However, we can still use the techniques presented in the paper to quickly validate genetic variants which can then be used in conventional breeding programmes. Selective breeding programmes use genotyping data of animals to identify animals and offspring of merit. The idea is to know which genetic sequences are important.

We can inform these breeding programmes that specific DNA sequences in their animals are beneficial and they can then pick the offspring carrying these DNA sequences for their breeding populations.”

“Heat resistance and disease resistance are the most important traits for our work with the Centre for Tropical Livestock Genetics and Health. For instance, the Frizzle feather genetic variant or ‘trait’ is hypothesised to cause the frizzly feather phenotype. Sometimes the background breed genetics of the animal is also important for the trait. We can now test now proven that a genetic variant or DNA sequence is causative for the trait. We have introduced the frizzle feather gene into the Light Sussex chicken and we will test if these chickens thrive at higher temperatures directly compared to Light Sussex chicken without the frizzle feather gene. This will prove that the frizzle feather gene on its own is beneficial for tropical environments.”

The study was published in Nature Communications and the work was funded by the Bill and Melinda Gates Foundation and the UK Foreign, Commonwealth and Development Office through CTLGH as well as UKRI and Innovate UK.