As part of a project launched by the Ural Federal Agrarian Research Center of the Ural Branch of the Russian Academy of Sciences, a team of geneticists, embryologists, biologists and veterinarians is developing a technology for editing the genome of cattle. The result was achieved three years later: scientists were able to get an animal with predetermined characteristics.
The idea of the project is to direct cutting-edge developments to create animals with improved traits in a short time – by directly introducing small changes in the genome. The participants of the experiments were black-and-white Holsteinized cows, a common breed of dairy cattle in the Urals.
Scientists worked with DNA regions responsible for susceptibility to leukemia, polled (hornless) and the production of hypoallergenic milk. Specialists used CRISPR/Cas9 technology, which allows you to change DNA fragments. Without innovative technologies, improving the characteristics of cows occurs traditionally, through breeding work, and this takes several decades.
“The development of a technique for transplanting an artificially grown embryo with gene correction into an animal is a large-scale and very laborious process. Over several years, a huge amount of research work has been carried out on the selection of donor material, its preparation for editing, a serious bioinformatics analysis has been performed, a system for making changes to the genome based on CRISPR/Cas9 has been created, and its improved version, packaged in adeno-associated virus (AAV ). At each stage, something did not work, did not work, and we carefully looked for the cause. The key to the success of the project was a wonderful team,” Anna Krivonogova, Project Manager.
Having chosen a section of DNA, the experimenters were looking for a way to block that section of the genome that was not needed. It was important to ensure that the modified area disappeared not only in the modified animal, but also in its offspring. “The embryo is changed already at the stage of one cell, but the body has a protective mechanism that constantly scans the DNA and eliminates the damage found in it. This mechanism helps organisms to survive, but it also prevents them from working with changes in genes. It was necessary not only to “break a section of the genome”, but also to do it in such a way that the defense mechanism would not notice,” explains Anna Krivonogova.
The first calf created using this technology has already been born, and now the team is watching its development. This is a female; her name has not yet been invented, and so far she has only one gene blocked – susceptibility to leukemia. Success at this stage gives hope that it will be possible to breed entire herds of animals with modified genes.
Leukemia is one of the most common infectious diseases in cattle worldwide. It is forbidden to use milk from sick cows, and this directly affects the efficiency of any livestock enterprise. Horned animals often injure each other and staff. To avoid this, calves have their horns removed in infancy, but such a serious intervention becomes stressful for them. And the absence of allergenic protein in milk allows not only to use it for people with allergies, but also to make infant formula and dietary products from it.
