Discovered in 2012, the system called CRISPR-Cas9 which makes it possible to isolate and cut DNA sequences offers the hope of correcting or eliminating, in the future that some see near, genetic disorders responsible for diseases.
A revolution is brewing. More than 15 years after the decoding of the human genome, we now have a tool that could make it possible to target a gene, eliminate it, correct it or replace it. A perspective that is both exciting and frightening: this technique is indeed an open door to transhumanism, that is to say the transformation with the help of scientific and technical knowledge of the physical and mental capacities of human beings.
This tool also has a name worthy of science fiction: CRISPR-Cas9. It makes it possible to cut a DNA sequence, to delete it or to modify it before re-implanting it. It is the principle of copying and pasting which authorizes a rewriting of the genome! The human applications would make it possible to treat at the same time the causes and the effects in many diseases linked to genetics, mental and hematological affections and obviously cancers.
A legislative framework not yet defined
But it is obviously necessary today to speak of it only in the conditional: these techniques on which research work is multiplying are not yet usable on humans since they require a legislative framework which has not yet been defined. .
The story of CRISPR-Cas9 began with research on bacteria. It was a researcher from the University of Osaka who spotted in the genome of Escherichia Coli somewhat special DNA sequences that could be read in both directions and thus formed palindromes which, at first interested anyone … Until it was discovered in 2005 that the pieces of DNA interspersed between these palindromes were pieces of DNA from viruses capable of infecting bacteria, the bacteria seeming to keep a memory in their CRISPR sequences the DNA of the viruses that have infected them, which makes it possible to identify and fight them. Later research demonstrated that, in bacteria, if a CRISPR viral RNA associated with the Cas9 protein crosses a virus with the corresponding DNA, it pairs up with this DNA and that once this coupling has taken place, the C9 protein eliminates the virus by cutting the two strands of its DNA.
It was this step that made it possible in 2012 to show that the CRISPR-Cas9 system made it possible both to locate a DNA sequence and to cut it with precision: the genetic scissors technique was born!
Limits in precision and efficiency
While this technique is quite widely used in agronomy to improve cultivated species or livestock, its application to humans still comes up against several obstacles. Ethics, first, but also linked to the limits of CRISPR-Cas9 in terms of precision and efficiency.
It will first be necessary to cross the barrier of antibodies since a proportion estimated between 65 to 79% of the population would possess antibodies against CRISPR-Cas9 type proteins and that the white blood cells of nearly one human in two would be specifically directed against these proteins. Moreover, if we know how to target a specific gene with CRIPR-Cas9, we do not know if its use on this target could not lead to other unwanted modifications in other places of the genome, which are called “off-target” modifications. This is what happened in 2015 when a team of Chinese geneticists modified human embryos to delete the gene for a blood disease.
Once these limits have been exceeded, however, scientists agree that we should see human applications appear within a few years. They indeed offer prospects such as the removal of cells, their extra-corporeal modification and their reintegration into the body to prevent or correct the genetic disorders which are at the origin of certain diseases or to better evaluate treatments.
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