In a world first a team of Chinese Enginers have used the CRISPR/Cas9 gene-editing technique to produce live cows with increased resistance to bovine tuberculosis successfully.
The team of engineers – from the College of Veterinary Medicine, Northwest A&F University in Shaanxi, China – used a modified version of the CRISPR technology to insert a new gene into the cow genome. Successfully avoiding the common problem off accidently causing “off-target” (unintended) effects in other areas of the genetics of the animal.
Dr Yong Zhang, the lead author of the study, said that the team used “a novel version of the CRISPR system” to “successfully insert a tuberculosis resistance gene, called NRAMP1, into the cow genome”.
Zhang was then “able to successfully develop live cows carrying increased resistance to the disease. Importantly, our method produced no off-target effects on the cow genetics meaning that the CRISPR technology we employed may be better suited to producing transgenic livestock with purposefully manipulated genetics”.
The team used a cell derived from female dairy cows—using the CRISPR/Cas9n technology to insert the NRAMP1 gene into the genome of “bovine foetal fibroblasts”.
These new cells were then used as donor cells and inserted into an egg cell; this was nurtured in the lab and then transplanted into mother cows for a normal pregnancy cyle.
Eleven of the calves with the new CRISPR genes have been found to have a resistance to tuberculosis while displaying no other genetic abnormalities.
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While the modified animals can only be classed as “resistant” instead of “immune”, it is still a significant step forward in the fight against bovine tuberculosis.
The successful use of CRISPR techniques on both cattle and crops look set to completely revolutionise agriculture in the same way that mechanisation did during the industrial revolution. It should create a completely new set of tools to fight disease and increase yields.
Unlike new antibiotics, new CRISPR changes to an animal’s DNA are not themselves the agent of resistance to a disease. Instead, the team are only using the technique to add an existing T.B. resistance gene to the cow genome.
If you were to think of the T.B. cells as engaged in a constant arms race with the cow’s immune system – the new genre means that the cow is now set to win that race. But, the white blood cells still have to hunt down the tuberculosis microbes, and while they are doing this, there is always slight chance that some T.B cells can produce a mutation – making T.B. cells resistant to the resistance. For this reason, the animals are said to be “resistant” instead of “immune”.
The full study, titled “Single Cas9 nickase induced generation of NRAMP1 knockin cattle with reduced off-target effects”, can be read in February’s Genome Biology (DOI: 10.1186/s13059-016-1144-4)
What is CRISPR?
Watch Kurzgesagt In a Nutshell explain how “Genetic Engineering Will Change Everything Forever”
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