CRISPR-Cas9: A History of Its Discovery and Ethical Considerations of Its Use in Genome Editing

Abstract

The development of a method for genome editing based on CRISPR-Cas9 technology was awarded The Nobel Prize in Chemistry in 2020, less than a decade after the discovery of all principal molecular components of the system. For the first time in history a Nobel prize was awarded to two women, Emmanuelle Charpentier and Jennifer Doudna, who made key discoveries in the field of DNA manipulation with the CRISPR-Cas9 system, so-called "genetic scissors". It is difficult to overestimate the importance of the technique as it enables one not only to manipulate genomes of model organisms in scientific experiments, and modify characteristics of important crops and animals, but also has the potential of introducing revolutionary changes in medicine, especially in treatment of genetic diseases. The original biological function of CRISPR-Cas9 system is the protection of prokaryotes from mobile genetic elements, in particular viruses. Currently, CRISPR-Cas9 and related technologies have been successfully used to cure life-threatening diseases, make coronavirus detection tests, and even to modify human embryo cells with the consequent birth of babies carrying the introduced modifications. This intervention with human germplasm cells resulted in wide disapproval in the scientific community due to ethical concerns, and calls for a moratorium on inheritable genomic manipulations. This review focuses on the history of the discovery of the CRISPR-Cas9 system with some aspects of its current applications, including ethical concerns about its use in humans.

Keywords: "genetic scissors"; CRISPR–Cas9; ethical considerations; genome editing.

Fig. 1.

Conventional classification of known CRISPR–Cas systems.

Fig. 2.

Historical timeline of discoveries of the components of the CRISPR–Cas9 system. 1987 – Short DNA repeats, later called CRISPR, were first noticed in bacterial genomes, and, in 1995, also found in archaea. 2005 – The role of CRISPR loci in the protection of prokaryotes from foreign genetic information was proposed, and the Cas9 protein was described for the first time (initial information on proteins associated with the CRISPR locus appeared in 2002). Two RNA molecules, crRNA and tracrRNA, were discovered as part of the complex in 2007 and 2011, respectively. The Nobel Prize-winning work, where all of the components were assembled in vitro and two RNA molecules combined into one strand for the ease of use of the system, was published in 2012.

Fig. 3.

Three-dimensional organization of the Cas9 protein in the complex with “guide” RNA (sgRNA) and substrate (Target DNA), crystallographic data (PDB ID 5F9R, PDB DOI: 10.2210/pdb5F9R/pdb).