Modification of Cas9, gRNA and PAM: Key to further regulate genome editing and its applications

The discovery of CRISPR-Cas9 system has revolutionized the genome engineering research and has been established as a gold standard genome editing platform. This system has found its application in biochemical researches as well as in medical fields including disease diagnosis, development of therapeutics, etc. The enormous versatility of the CRISPR-Cas9 as a high throughput genome engineering platform, is derailed by its off-target activity. To overcome this, researchers from all over the globe have explored the system structurally and functionally and postulated several strategies to upgrade the system components including redesigning of Cas9 Nuclease and modification of guide RNA(gRNA) structure and customization of the protospacer adjacent motif. Here in this review, we portray the comprehensive overview of the strategies that has been adopted for redesigning the CRISPR-Cas9 system to enhance the efficiency and fidelity of the technology.