Mario Capecchi, Oliver Smithies and Martin Evans made gene modification, gene therapy and especially the so-called knock out mouse world famous. Many new treatments and specific gene modifications and cloning became possible. In 2020, gene knockout, gene knockdown and gene knockin are used. It is explained what type of research this involves.
Gene therapy, genes and proteins
The proteins in our body are vital. They not only ensure that chemical reactions proceed correctly and that connective tissue and bone are strong. They transport essential substances, communicate between cells and so on. The trick now is that all genes together determine our physical properties and each individual cell picks up the information it really needs. The cell switches on what it needs, as it were, but not the rest. For example, hemoglobin only occurs in red blood cells, even though all cells in our human body can in principle have this hemoglobin gene.
Knockout
Here we come to the essential characterization of what is called knockout in gene therapy. No unconsciousness of a cell, but rather a conscious switching off of properties in order to better understand what the properties of a gene are. In a gene knockout, a gene is removed from the DNA.
Gene knockdown
In a gene knockdown, the expression level of a gene or genes is reduced, it is less active but not deleted or completely disabled. The gene is suppressed or (temporarily) silenced. In the event of a knockout, there is a chance that the cell will also be killed and then you will not have made much progress. With a knockdown, the functioning of the cell can often still be studied well, albeit with a less active gene present.
Gene knockin
The gene knockin involves inserting a new gene into the body’s DNA. This is a complicated technique of cutting, pasting and repairing that is being extensively researched in 2020.
Genetic code
In humans, approximately the entire genetic code is known, but we do not yet know all the properties in the body. All cells in the body have the same genetic information, but because not every cell has the same functions, not all genes are switched on and therefore the functioning of a cell is different. This switching on and off and making changes teaches us a lot about how genes work. The body knows why a gene is on or off, humans are trying to map this out experimentally.
Transgenesis
We don’t yet know exactly what is switched on and off in our body and why. To find out the function of a gene, we can try to make changes in the body and carefully study what changes as a result and what the effect of this change is. We call this gene modification via trangenesis. A mouse is often used as a laboratory animal.
The promoter of a gene
The promoter plays an important role. The promoter of a gene is a piece of DNA located in front of the gene that determines whether, when and to what extent a gene is on or off. It is also possible that a promoter is not working, is not working sufficiently and can be improved. To gain more clarity about this, the promoter in question is linked to a gene that produces a green fluorescent protein. The coloring makes it easy to monitor the production and you can see whether the promoter is working correctly or not.
The laboratory and knockout genes
Hereditary diseases are caused by mutated or disabled genes. Scientists would also like to be able to demonstrate exactly which buttons you need to turn to reverse a disease. Incorrect knockout genes are isolated in the laboratory and then introduced into a very young mouse embryo. This creates a so-called chimeric mouse in the surrogate mother mouse. That is, a mouse that consists partly of cells with the knockout gene and partly of normal cells. By further crossing mice, a mouse is created with only certain knockout genes.
Nobel Prizes
The Nobel Prize for Medicine in 2007 went to the American biologists Mario Capecchi and Oliver Smithies and the British Martin J. Evans. They now developed the technique to switch individual genes in a laboratory animal on and off. This technique made cloning and genetic modification possible, further opening the way to successful gene therapy. After a drug has been developed, it still needs to be approved, which is often a long process. In 2020, Spinraza received conditional approval and many more drugs are expected to follow.
Knockdown in 2020
These are complicated techniques, it all started with switching off a gene (knockout) and that still seems relatively simple. In 2020, the eyes of science are more focused on knockdown and knockin. There is still a long way to go.