Gene editing could rid sheep of problematic long tails – WSU Insider

Longer queues have long given sheep producers worldwide problems, but a research project led by Washington State University graduate student Brietta Latham could eliminate the trait.

While breeds in other regions naturally have short tails, most domestic sheep have longer tails which can lead to hygiene problems and health problems, including fly strike, a painful and potentially deadly condition caused by blowflies that they lay their eggs on sheep. The industry standard has been to dock the animals’ tails, which can be painful for sheep and time-consuming and costly for producers.

Latham was recently awarded a three-year grant from the United States Department of Agriculture for his proposal to develop a gene-editing strategy to shorten the tail of Suffolk sheep and eliminate the need for tail docking. Suffolk sheep are one of the most produced sheep in the United States

Our research will offer the industry an alternative to tail docking and improve animal welfare in our food production systems, Latham said. It will also improve production efficiency as we won’t have to deal with the costs and labor associated with tails removal.

Humans have influenced genetics for centuries to select for desirable traits in both plants and animals. Traditionally, this has been achieved through selective breeding, which can take generations to achieve the desired results. Latham, in his second year of doctoral studies with Professor Jon Oatley at WSU’s School of Molecular Biosciences, expects to achieve this in a fraction of the time.

Genetic modification has been around since we started breeding pets whenever we choose to breed an animal with another animal to enhance a certain productive trait, that’s us performing the genetic selection, Latham said. We’re actually just speeding up the process by using gene-editing tools in the lab.

Brietta Latham, a doctoral student in WSU’s School of Molecular Biosciences, stands next to a tank containing beetles and caterpillars scavenging the skeletons of mice used in research to develop a gene-editing strategy to shorten the tails of Suffolk sheep and eliminate the need for tail docking. (Photo by College of Veterinary Medicine/Ted S. Warren)

With CRISPR-Cas9, researchers like Latham can precisely edit specific sections of a cell’s genome by removing, adding, or altering genes.

Previous genetic research has identified the gene suspected to be responsible for tail length in sheep. Latham plans to knock out or remove that gene in the embryos of long-tailed sheep and replace it with the gene found in short-tailed breeds. He used his own strategy to successfully shorten the tails in mice.

This is a modification that already exists in sheep. We’re just taking this change that we see occurring in short-tailed sheep in China and Iran and putting it into sheep of European descent that have long tails, Latham said.

The modified embryos will be transferred into ewes which, after a gestation period of five months, are expected to give birth to healthy lambs with short tails. Those lambs should be able to pass the desired trait on to their offspring.

The most important thing with gene editing is to make sure you get what we call germline transmission. We want the changes to show up in the gametes, eggs and sperm that the modified animal is producing, he said. This is how we get the transmission from generation to generation.

People often mistakenly confuse gene editing with the more controversial gene modification through transgenesis. Gene editing does not combine DNA from other species or attempt to create something that would never happen in nature. Instead, gene editing seeks to make desirable changes in an animal species that could occur naturally but could take decades using selective breeding.

This is a modification that is naturally seen in sheep that people are eating, Latham said, so we know it is safe to put in animals and that it won’t harm them or the people who are consuming them.

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