Hornless cattle have healthy offspring and unintended modifications

A multi-year study of genetically modified cattle proved that its offspring is physically healthy, and preserves introduced trait – lack of horns. However, at the same time their genomes carry bacterial genes introduced unintentionally from genetic tools.

Horns in cows are an attractive target for genetic modifications. Farmers express the need for hornless bulls, and we know the natural genetic change that leads to loss of horns. That’s why in 2015 the world saw the first GM hornless cows. Since then, researchers have been assessing the inheritance, safety, and health of those animals.

The results were presented in two parts. Federal Drug Agency posted a preprint (not peer-reviewed article) with concerns about off-target integration of a plasmid (genetic modification tool) in the genome of cattle. A few months later, the team from UC Davis published an article with a detailed analysis of cattle and their offspring. They confirmed the presence of plasmids in four out of six calves. At the same time, they thoroughly assessed the health of the calves, reporting the lack of any veterinary issues.

Publication: Young, A. E., Mansour, T. A., McNabb, B. R., Owen, J. R., Trott, J. F., Brown, C. T., & Van Eenennaam, A. L. (2019). Genomic and phenotypic analyses of six offspring of a genome-edited hornless bull. Nature Biotechnology, 1-8. Doi:10.1038/s41587-019-0266-0.
Preprint: Norris, A. L., Lee, S. S., Greenlees, K. J., Tadesse, D. A., Miller, M. F., & Lombardi, H. (2019). Template plasmid integration in germline genome-edited cattle. BioRxiv. Doi:10.1101/715482.

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