CRISPR/Cas9 mediated genome editing: Applications and clinical studies

Eukaryotic species' genomes are made up of billions of DNA bases. The ability to modify these DNA bases at specific predetermined positions is extremely valuable not only in molecular biology, but also in medicine and biotechnology. Genome editing has long been a priority in molecular biology. The late 1970s discovery of restriction enzymes that usually defend bacteria. against phages was a defining moment that fueled the era of recombinant DNA science. It was later discovered that the introduction of a double-strand break (DSB) at a target site increases the frequency of selective gene incorporation by many orders of magnitude. While artificially conceived meganucleases, followed by Zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENS), enhanced genome editing performance, re-design or re-engineering of a new category of proteins was needed to target different sites in the genome. The challenge in cloning and protein engineering ZFNs and TALENS hampered their widespread adoption by the scientific community. CRISPR has transformed the industry in this regard because it is as powerful as, if not more so than, existing editing tools (1). Furthermore, it is much simpler and more adaptable to use. A brief timeline of key events in the discovery and subsequent repurposing of CRISPR/Cas9 system for gene editing is mentioned in table 1.