CRISPR/Cas9 – The Gene Scissors Open a New Era in Genetic Engineering

Since 2012, the CRISPR/Cas9 gene scissors have become the leading method for “genome editing” and are opening up a new era in genetic engineering.

Here, an RNA molecular sequence that binds to a specific section of DNA is combined with an enzyme that cuts the DNA double strand at this specific site. The resulting defect is then repaired by the cell’s own enzymes. In most cases, the two ends of the DNA can be joined directly, which leads to a shortening and alteration of the gene sequence. What is special about the CRISPR/Cas9 gene scissors is that the desired region of the genome can be cut and at the same time also replaced or switched off. In addition, individual nucleotides in a gene can be changed.

 

The discovery of the CRISPR/Cas9 gene scissors

This revolutionary procedure is based on a proven immune strategy used by bacteria against viral infections. Bacteria have developed a method of detecting foreign gene sequences. The DNA sequences originating from viruses are integrated into the genome, causing the bacterial cell to involuntarily replicate new viruses. In the course of evolution, some bacterial species have developed the ability to recognise this segmental viral DNA and cleave it enzymatically. In this way, the danger is eliminated before the viral intruders can be integrated into the genome. This mode of action of the immune system is called CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats).  

The first indication of this extraordinary immune system concept came in 2007, when a yoghurt company reported on a defence mechanism of bacteria against viruses. The first scientific documentation of the use of the method was only published in 2012 by a working group led by Emmanuelle Charpentier and Jennifer Doudna. Jennifer Doudna and her colleagues showed that this “scissors” can be programmed in such a way that any section of DNA in the genome can be switched off, removed or replaced. For harnessing this ancient bacterial immune system as a reliable, low-cost gene-editing technology, Emmanuelle Charpentier and Jennifer Doudna received the 2015 Breakthrough Prize – the “Oscars of Science” – with prize money of 3 million dollars. This award has been presented since 1996 by the scientific journal Science.

CRISPR/Cas9 gene scissors attract worldwide attention

Since then, this procedure has become increasingly established in everyday scientific work. Since 2014, the number of publications mentioning the CRISPR system has risen steadily. The number of relevant publications rose from a few hundred in 2014 to around 3,600 in 2017. Articles on the use of CRISPR/Cas9 in bacteria, fungi and various plants appear every day. There are now even application kits, e.g. DIY CRISPR kits for private use, available online for around $140. This revolutionary technology is thus already affordable.

Ethical discussions about CRISPR/Cas9 gene technology

This new technology will fundamentally influence all our lives, to an extent that we cannot yet assess. The comparison of this revolution with developments in Silicon Valley in the 1980s and 1990s seems quite apt. Could we have imagined back then the applications in our everyday lives that are possible today? Discussions are already being held on several platforms about what our new future could look like. In addition to the seemingly endless possibilities, the ethical limits of this technology are also being addressed. Is it permissible to intervene so deeply in nature, and above all in human nature? Will we one day want to use this technology not only for medical purposes but also to modify our bodies? There is talk of the “genetic plastic surgeon” and the “gene surgeon”. Will we want to exhaust all these possibilities? The social classes who can afford these treatments will thus create further advantages for themselves. Do we want to live for hundreds of years, equip our children genetically against diseases, programme them to be more intelligent and more beautiful before they are born? How could such developments influence our social system and how we live together? An exciting new era has already begun, of which many are not yet fully aware. The influence of CRISPR technology on our lives will only become noticeable in the coming decades.  

Sources and further information

• The Nobel Prize in Chemistry 2020: press release (Emmanuelle Charpentier, Jennifer A. Doudna)
• Jinek M, Chylinski K, Fonfara I, Hauer M, Doudna JA, Charpentier E: A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science 2012; 337(6096): 816–821.
• Innovative Genomics Institute: CRISPR Clinical Trials – 2026 Update