CRSPR/CAS9 Technology: A Revolutionary Molecular Scissors for Genome Editing and Genetic Research

Abstract

Targeted gene modifications to animals' especially mammalian genomes are central to understand the role of the gene in development, physiology, and different disease conditions. Functional elucidations of a gene or genetic variants require precise editing technologies. In conventional gene targeting methods, mutations of the gene or gene has been introduced into the genome by homologous recombination in embryonic stem (ES) cells and then injected into wild-type Blastocyst to generate chimerical animal models containing the targeted gene modification. Although it is widely used approach, however, it is laborious, time-consuming, and expensive, needing well-trained researchers. Moreover, in most of the mammalian species, established ES cell lines are not available to produce chimeric animals, which limits the traditional approach. The recent discovery of new genome-engineering tools, especially CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/ CRISPR-associated) overcome much of the difficulties. CRISPR is a microbial nuclease system that is involved in defense against genome invading phages and plasmids. It has been experimentally proven that the Cas9 end nuclease from Streptococcus pyrogens type II CRISPR/Cas system can be programmed to produce sequence-specific double strand breaks (DSBs) in vitro by providing a synthetic guide RNA (gRNA-fusion of crRNA and tracrRNA). There are lots of researchers that have illustrated that the CRISPR/ Cas9 system can be used to generate different gene deletions or replacement in mammalian as well as in model organisms. In this review, we will discuss the pros and cons of the system and briefly discuss the future direction.