ABSTRACT
Clustered regulatory interspaced short palindromic repeats (CRISPR) and the protein associated with it called Cas9 is considered a competent RNA-mediated molecular scissor for editing genomic segments in all living cells. CRISPR-Cas9 is a defence mechanism against viruses that evolved in bacteria, where the Cas9 nuclease guided by single-strand RNA attaches to a complimentary viral genetic material strand. CRISPR-Cas9 is an innovative approach in genome editing that involves three steps: recognition, cleavage and repair. Two key components of the CRISPR-Cas9 technique involve sgRNA that recognizes target segments within a gene of interest that are complementary and Cas9 that introduces a double-strand break (DSB) three bases upstream of the protospacer adjacent motif (PAM). This DSB is later repaired by non-homologous end joining (NHEJ). Therefore, by using this technique, DNA sequences within an endogenous genome can be easily edited, thus manipulating its function. This tool has a broad spectrum of applications, but here, we strictly focus on different areas of disease biology including but not limited to sickle cell anaemia, cancer, cystic fibrosis and Duchenne muscular dystrophy. However, immunogenicity, off-target effects and ethical issues are certain barriers for extending this powerful tool to clinical trials.
