Gene-editing used to create single sex mice litters

Scientists at the Francis Crick Institute, in collaboration with University of Kent, have used gene editing technology to create female-only and male-only mice litters with 100% efficiency. This proof of principle study, published in Nature Communications today, demonstrates how the technology could be used to improve animal welfare in scientific research and perhaps also agriculture. In scientific research and also farming, there is often a need for either male or female animals. For example, laboratory research into male or female reproduction requires only animals of the sex being studied. And in farming, only female animals are required for egg production and in dairy herds. This means it is common practice for animals of the unrequired sex to be culled after birth. The researchers’ new method uses a two-part genetic system to inactivate embryos shortly after fertilisation, allowing only the desired sex to develop. Such a genetically-based method to control the sex of offspring could drastically reduce culling in both industries. The embryo selection is based on the fact that there are two elements of CRISPR-Cas9—the Cas9 enzyme that cuts the DNA, allowing scientists to alter specific regions, and the guide RNA which carries the Cas9 to the right location on the genome. The team placed one element of the system on the father’s X or Y chromosome, meaning that it will only be inherited by female or male embryos respectively. The other element is contributed by the mother, and is inherited by all embryos.

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