CRISPR/Cas9 – the magic cure?
This year’s Nobel prize in chemistry went to Emmanuelle Charpentier and Jennifer Doudna for discovering the method of genome editing in humans using CRISPR/Cas9. Just like a single typo in a computer code can make the whole program malfunction, a small error in the DNA – the universal code of life – may cause serious health problems. Examples of such errors are all types of genetically inherited diseases such as pediatric blindness or sickle-cell anemia, but also spontaneous and induced mutations like neoplasms. Presently, we can treat such diseases only symptomatically, but we are unable to eradicate them on the DNA level. This is when CRISPR (short for Clustered Regularly Interspaced Short Palindromic Repeats), comes in.
CRISPR/Cas9, consisting of the guide RNA, along with the CRISPR associated protein – Cas9, is a biological tool used by prokaryotes (bacteria and archaea) to repair DNA damages. This immune response differs from that of eukaryotes (animals and plants), which is based solely on RNAi. RNAi can only reduce the expression of the mutated gene, whereas CRISPR/Cas9 removes it completely. How? – Guide-RNA detects the mutation and guides the Cas9 protein to it. Cas9 then cuts out the faulty fragment of the DNA so it can be replaced with a correct sequence.
Now, what stands in the way of using CRISPR/Cas9 to cure cancer and other DNA-related diseases? Although it could be used in humans, this biological tool would have to be specially programmed to target specific mutations in human DNA, since it naturally occurs only in prokaryotes and has evolved to repair solely prokaryotic DNA. Scientists have been working on this biotechnology since Emmanuelle Charpentier and Jennifer Doudna published their research on how CRISPR/Cas9 could be used in humans, back in 2012. Progress has been made, and some genetic therapies are currently in the late stage of clinical trials. However, there is still no 100% guarantee that CRISPR/Cas9 will not alter healthy fragments of the DNA, causing another mutation.
CRISPR/Cas9 is such a universal tool, which could be used not only for repairing DNA to treat genetic disorders, but also for altering genes in an unnatural way. This is when ethical issues arise. Should we alter human, or even plant DNA? It would definitely pose a threat to the genetic diversity of the global ecosystem. Natural evolution is a fair competition that allows all species to adapt and enhance simultaneously, letting the best players survive. Genetic modification, on the other hand, would oppose natural selection by enhancing only some species (plants and animals of commercial value), and thus making them invasive if spread into the natural environment. This could lead to the extinction of other, not genetically modified species. Altering human DNA would be especially unethical, as it could escalate socio-economic inequalities. It is not too early to think about the consequences of redesigning the code of life on demand. Certainly, the focus should be on repairing DNA to treat (currently) incurable diseases, and not on biohacking. Perhaps you, dear reader, would like to become a genetic engineer and improve the accuracy of CRISPR/Cas9?
Image source: https://www.britannica.com/