Many scientists and animal breeders are very interested in directly altering a part of an organism's genome to incorporate specific traits. For example, Recombinetic recently created two bulls by introducing specific genes through gene editing. Breeding can currently be carried out by identifying bulls or cows carrying specific dominant genes. Recombinetic's bulls differ in that these animals are clones of horned bulls.
The aim of this work is to create clones that are genetically identical to the initial horned bulls, in addition to the desired genes. The work was largely successful, and the two bulls have been moved to the University of California, Davis for further evaluation. One of the bulls then mated with horned cows and all offspring were followed, and the results showed that the desired gene had been successfully integrated into the genome.
A faster future
Performing intentional genomic alterations (IGA) can speed up genetic selection. In most cases, gene editing is of little help for traits such as milk production, but there are many other ways. The genotypes that can be changed relatively quickly are:
Homozygotes;
A2 β casein genotype;
Non-recessive genes;
Smooth hair genes that improve heat tolerance;
The gene for optimal cheese yield.
Many of these tasks are currently being done through bull selection, but using the current model will take a long time. Theoretically, gene editing could do everything in one generation. So you can see why many people are interested in this.
The technology to create gene-edited organisms relies on systems of bacteria. While the above bulls were created using TALENs systems, the most famous of these systems is CRISPR/Cas9. Regardless of the gene-editing system, specific DNA sequences are targeted to be added or knocked out to alter the genome. Typically, gene-editing systems are designed to work in specific regions of the genome.
In the case of specific genes, scientists are replicating natural mutations that occur in cattle, and may also introduce new mutations. Gene-edited pigs are already resistant to porcine reproductive and respiratory syndrome (PRRS).
The PRRS virus has had a devastating impact on the U.S. pig industry, causing pregnant sows to miscarry and killing piglets. The scientists studied how PRRS viruses attack cells and noticed that they used specific proteins expressed on the surface of pig cells. They used gene editing to knock out the genes that code for the protein. Pigs are therefore resistant to the PRRS virus, which also indicates the potential for gene editing to be used in animal husbandry.
Potential regulations
Most scientists believe that genetically edited cattle and pigs are safe for humans. Such technologies are regulated by various government agencies, and regulations vary from country to country. Governments in South American countries, such as Brazil, often tend to allow the use of such technologies. But only if the company doesn't introduce genes from one species into another, the creatures created are considered genetically modified organisms (GMOs).
Attitude of the United States
The U.S. Food and Drug Administration (FDA) has taken a more restrictive stance. They have made it clear that IGA regulation will be roughly the same as the introduction of new antibiotics and new drugs. The process required to obtain a new drug approval is very lengthy and very expensive. Many scientists and companies involved in gene editing have severely criticized the FDA's position and views.
Scientists involved in the gene-editing bull study decided to try their luck. They informed FDA regulators that they wanted to slaughter the bulls because most of the research projects had been completed.
The good news is that the requirement did allow the FDA to speed up the evaluation of gene-editing bulls. Scientists at the FDA measured the bull's genome sequence and reported that the changes were indeed made at the expected site.
What's the bad news?
Although the change is made at the expected site, the type of change is not exactly the expected result. In addition to the desired mutations, they also found bacterial DNA in the bull's genome. The scientists involved in the project have measured the genome to ensure that the desired mutations are properly integrated, but they ignore the possibility that bacterial genes may be introduced at the same time.
This may sound like a serious oversight, but it may not come as a surprise to those sequencing the genome. Integrating an animal's DNA sequence is not an easy task, just as all people inherit about 6 billion PAIRs of DNA bases from their parents, but can't read the entire genome from beginning to end like reading a book.
SCIENTISTS AT THE FDA screened the bacterial genes more directly. They also found that a cow was introduced into multiple variants, not just one.
The presence of bacterial DNA immediately changes the state of such animals from IGA to GMO. This change means that more regulations will be enacted in the United States or in countries with previously more relaxed policies.
As far as plants are concerned, GMOs are common. But for animals, there are very few, and the only GMO product is salmon produced by a company called AquaBounty. It took AquaBounty about three decades to get FDA approval to sell its products in the United States.
Looking to the future
Scientists react differently to these latest developments. Some point out that bulls were created with older technologies, while newer ones are less prone to such results. Even with this change, the food produced is still safe.
Others point out that gene editing is still a relatively new technology and that there is still a lot to learn. Some warn that there are more potential mutations than expected, and believe that the latest research developments confirm these concerns.
The field of gene editing is rapidly evolving, but these latest developments may have some negative effects to some extent. Therefore, for those who want to change the traits of cattle such as A2 milk and smooth genes through gene editing, it seems that there should be a need to use good bulls and cows for genetic selection until gene editing becomes an officially approved way of genetic improvement, a model that has been practiced for a long time and will continue.