CRISPR/Cas9 genome editing system

Biomedical Applications of CRISPR/ Cas9 Genome Editing System The clustered regularly interspaced short palindromic repeat (CRISPR) and associated protein 9 (CRISPR/cas9) gene editing system enables manipulation of any gene in cells and tissues originally associated with the adaptive immune system of Streptococcus pyogenes. CRISPR/cas9 induces double strand DNA breaks (DSB) in the genome at precise, predetermined loci. The essential CRISPR-Cas components constitute the Cas9 RNA-guided endonuclease which cuts DNA at a specific site, a singleguide RNA (sgRNA) that carries a sequence (protospacer) complementary to the DNA target and a short sequence in the target called the protospacer-adjacent motif (PAM) essential for Cas9 binding. The system enables replacement or modification of the aberrant/diseased gene by insertion or deletion in the genome at the precise position. The applications of the system, capable of simultaneous alteration of multiple genes, are immense in the areas of agriculture and biomedical fields and are of critical value in the current scenario. Thus tackling almost insurmountable, global, biomedical problems such as antimicrobial drug resistance, reversal of hereditary gene defects, and complete cure in cancers with currently no known cure, is feasible. The future envisaged is symptomatic treatment with the endpoint of a complete cure and/or reversal of the disease progression. New delivery systems to induce permanent effects safely will be a requirement for clinical applications. The drawback is the nonspecific recognition and digestion of non-target sites, introducing mutations at off-target sites with untoward effects in treatment of human disease. Inroads have been made using the system towards treatment in monogenic diseases such as β-thalassemia, sickle cell anemia, Duchenne muscular dystrophy, neurodegenerative disease including Huntington's disease, Parkinson's disease, Amyotrophic lateral sclerosis Dhananjaya Saranath and Aparna Khanna