The use of gene editing tools may be an efficient approach in tackling genetic diseases since they are predominantly caused by mutations in specific alleles. Clustered regularly interspaced short palindromic repeats and associated nucleases (CRISPR/Cas) is one such tool. CRISPR has the ability to create knockouts, knock-ins, minute mutations and is more precise, inexpensive and quicker than the others.
A few years ago, a statement like “bacterial immune systems can potentially serve as a breakthrough in gene editing” would have probably sounded ridiculous. However, in 2007 scientists from Denmark showed how a bacterium that was previously exposed to a viral phage became immune to it. Soon after, it’s immune system and peculiar ability to remove, insert, stimulate or suppress specific genes was collectively understood. Of the many CRISPR systems, CRISPR/Cas9 is the most popular, as it requires only a nuclease and a guideRNA to target and cleave specific sequences of DNA. The Cas9 protein has the ability to recognize sequences just few bases in length if present next to a Protospacer Adjacent motif site (a sequence of specific nucleotides in the DNA) and create a double strand break in the DNA followed by repair of the break-joining the broken ends, resulting in removal of target sequence.
The applications of this technique in medicine is far-reaching. From manipulation of nucleotides at the genetic level, understanding of mutation caused metabolic pathways, creation of novel engineered animal model systems that mimic disease pathology and large scale drug screening can be used to gain insight into several under-researched diseases and in addition, potentially throw light on their epigenetic influence.
Despite the hype, CRISPR has received its fair share of backlash in terms of possibly being misused and resulting in unprecedented penalties, more so due to its ease of accessibility. A documentary on Netflix called Unnatural Selection discussed the concept of biohacking and how easily it can be conducted in one’s backyard! In addition, limitations of this technique include off-target mutations due to high copy numbers of certain genes or very similar recognition sequences resulting in deleterious consequences, toxicity due to plasmids, unwanted in-dels after double strand break repair via non-homologous end joining among others. However, CRISPR has the potential to contribute to disease therapy if a balance can be drawn to establish safe and ethical use of the technique.
Read more on the applications of CRISPR at: https://doi.org/10.1038/nprot.2013.143
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