CRISPR technology may not yet be used to cure diseases in humans, although studies on animals have shown that the gene editing technique has excellent potential for the treatment of genetic disorders and disease. Perhaps none more so than a recently published study conducted by researchers at the College of Veterinary Medicine at Northwest A&F University in Shaanxi, China.
The team has successfully used CRISPR technology to produce tuberculosis-resistant cows. A new gene was inserted into the cow genome using CRSIPR technology and live cows have now been born with increased resistance to bovine tuberculosis.
While CRISPR technology is believed by many to be safe, there is a risk of unintentional off-target genetic alterations being made. However, the researchers have failed to detect any off-target effects when editing the genome of cows.
CRISPR technology uses guide RNA to bind to specific genes, while a CRISPR associated protein (Cas9 for example) is used to cut the DNA at a precise location. The technology can be used to remove sections of DNA, or in this case add in new genes. In this study, the researchers added a tuberculosis-resistant gene called NRAMP1 to the cow genome.
One problem for the researchers was determining the best location in the cow genome to insert the new gene. There was potential for the new gene to have an impact on other genes that were in close proximity, although the team used a “meticulous and methodical approach” to determine the most suitable location to minimize any negative effects.
Once the ideal location was selected, the team inserted the new gene into the genome of bovine fetal fibroblasts obtained from dairy cows. Using somatic cell nuclear transfer, the nuclei were transferred into cow ova. The ova were developed into embryos in vitro and the genetically modified cow embryos were subsequently transferred to cows to complete development through the normal pregnancy cycle.
11 calves have now been born and the animals will be monitored for any negative effects, as well as for resistance to tuberculosis. The calves have already been exposed to M. bovis and have shown increased resistance to the disease.
Lead author of the study, Dr. Yong Zhang, said “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 success of the researchers has caused considerable excitement over the potential for CRISPR technology to be used to prevent tuberculosis in humans. The disease is contracted by around 10 million people worldwide and is responsible for the deaths of over 2 million people each year.