Gene editing is defined as any genomic engineering process by which DNA is inserted, removed or replaced by nuclease enzymes . Beyond the definition of “book”, this type of practice leads to a series of ethical considerations that of course must be taken into account. In 2015, the first attempt at genetic modification of a human embryo was given the green light, followed by experimentation that sought to improve the resistance of these unborn infants to HIV. Crispr cas9 definition
Following this, in April 2016, Nature News magazine reported that Professor Fredrik Lanner’s research team from the Karolinska Institute in Stockholm had received the necessary ethical approval to begin research that included editing human embryos, a practice strictly prohibited until just a few years ago.
The barrier has been crossed: the experimental field is no longer limited only to laboratory animals or the treatment of chronic patients , but the human being is potentially capable of modifying the attributes of people even before they are born. Of course, with these findings, questioning whether gene editing is dangerous is extremely common in the general population.
What is CRISPR-Cas9?
This technique requires its own mention, since it has popularized in the world of science the “gene targeting” or gene targeting. While the modification and use of the zinc fingers costs an average of 30,000 euros per experiment, with CRISPR-Cas9 only a couple of weeks of work and a budget of 30 euros are needed . Even if only for economic reasons, this methodology has opened countless doors in the world of genetic engineering.
To understand this technique we have to understand the two components of its name. Let’s go there:
- CRISPR: a genetic region of some bacteria that acts as an immune mechanism against some viruses.
- Cas9: an enzyme that acts as a “genetic scalpel”, that is, it cuts and adds new regions of DNA to it with great precision. Crispr cas9 definition
In general, we could say that the CRISPR-Cas9 system is responsible for destroying the regions of genetic material of the virus that has infected the bacteria , inactivating its pathogenic capacity. Beyond that, this sequence allows the integration and modification of regions of viral DNA in the bacterium itself. In this way, if the virus re-infects the microorganism, it will “know” its nature much better and act more efficiently against it.
To keep things simple, we will say that this methodology allows DNA modification at the cellular level, since cuts and modification do not apply only to viral components. The RNA encoded in the CRISPR DNA region acts as a “guide dog”, guiding the Cas9 enzyme to the exact place in the cell’s DNA where cutting and gluing of genetic sequences have to be made. Although it requires an important exercise in abstraction, this technique is still a most fascinating microscopic mechanism.
The lowering of costs and the ease of use of this technique have represented a new stage for genomic engineering , which, without exaggeration, represents a new window for the concept of human life and evolution as we know them. But is genetic engineering dangerous?
Discovery of CRISPR
The discovery of clustered DNA repeats occurred independently in the 1980s and 1990s by researchers in Japan, the Netherlands and Spain. The acronym CRISPR was proposed by Francisco Mojica and Ruud Jansen in 2001 to reduce the confusion caused by the use of different acronyms by different research teams in the scientific literature. Mojica assumed that CRISPRs were a form of acquired bacterial immunity. In 2007, a team led by Philippe Horvath verified this experimentally. It didn’t take long for scientists to find a way to manipulate and use CRISPRs in the lab. In 2013, Zhang’s lab became the first to publish a method for engineering CRISPRs for use in genomic editing in mice and humans. Crispr cas9 definition
How CRISPR works
Essentially, naturally occurring CRISPR provides a cell search and destruction capability. In bacteria, CRISPR works by transcribing spacer sequences that identify the DNA of the target virus. One of the enzymes produced by the cell (eg, Cas9) then binds to the target DNA and cuts it, turning off the target gene and inactivating the virus.
In the lab, Cas9 or another enzyme cuts the DNA, while CRISPR tells you where to cut. Instead of using viral signatures, researchers customize CRISPR spacers to search for genes of interest. Scientists have modified Cas9 and other proteins, such as Cpf1, so that they can cut or otherwise activate a gene. Turning them on and off makes it easier for scientists to study the function of a gene. Cutting a DNA sequence makes it easier to replace it with a different sequence.
Why use CRISPR?
CRISPR is not the first gene editing tool in the molecular biologist’s toolbox. Other techniques for gene editing include zinc nucleases (ZFN), transcriptional activator-like effector nucleases (TALENs), and genetically engineered meganucleases from mobile genetic elements.
CRISPR is a versatile technique because it is cost-effective, allows for huge targeting, and can target locations that are inaccessible to certain other techniques. But the main reason is that it’s incredibly simple to design and use. All that is needed is a set of 20 nucleotides, which can be done by building a guide. The mechanism and techniques are so easy to understand and use that they are becoming standard in undergraduate biology curricula. Crispr cas9 definition
Uses of CRISPR
Researchers use CRISPR to make cell and animal models to identify genes that cause disease, develop gene therapies, and design organisms to have desirable traits.
Current research projects include:
- Applying CRISPR to prevent and treat HIV , cancer, sickle cell disease, Alzheimer’s, muscular dystrophy and Lyme disease. Theoretically, any disease with a genetic component can be treated with gene therapy.
- Develop new drugs to treat blindness and heart disease. CRISPR/Cas9 has been used to remove a mutation that causes retinitis pigmentosa.
- By extending the shelf life of perishable foods, it increases the resistance of crops to pests and diseases and increases nutritional value and yield. For example, a team at Rutgers University used the technique to make grapes resistant to downy mildew .
- Pig organ transplantation in humans without rejection.
- Bring back woolly mammoths and maybe dinosaurs and other extinct species.
- Making mosquitoes resistant to the malaria- causing Plasmodium falciparum parasite .
Obviously, CRISPR and other genome editing techniques are controversial. In January 2017, the US FDA proposed guidelines to cover the use of these technologies. Other governments are also working on regulations to balance benefits and risks. Crispr cas9 definition