Genome editing refers to a type of genetic engineering in which DNA is replaced, deleted or inserted in the genome of a living organism using engineered nucleases. These engineered nucleases enable efficient and precise genetic modifications by inducing targeted DNA double-strand breaks (DSBs) that stimulate the cellular DNA repair mechanisms, There are currently three families of engineered nucleases being used, zinc finger nucleases (ZFNs), transcription activator-like effector-based nucleases (TALEN), and the CRISPR-Cas system.

The mechanism of ZFN and TALEN system

ZFN and TALENs undergo similar molecular mechanisms for executing genome editing. ZFN and TALENs are both engineered nucleases composed of a DNA binding domain that recognize a specific nucleotide triplet based on the residues in their helix and a FokI nuclease motif that have a strong catalytic cleavage capability for specific nucleotides. The FokI domains must dimerize for activity, thus increasing target specificity by ensuring that two proximal DNA-binding events must occur to achieve a double-strand break (DSBs). These chimeric nucleases enable efficient and precise genetic modifications by inducing targeted DNA DSBs that stimulate the cellular DNA repair mechanisms, including error-prone non-homologous end joining (NHEJ) and homology-directed repair (HDR).

The mechanism of CRISPR system

CRISPR is a ubiquitous family of clustered repetitive DNA elements present in 90% of Archaea and 40% of sequenced Bacteria. The CRISPR system was first identified as an adaptive defensive mechanism that confers resistance to foreign genetic elements. Later on, CRISPR-Cas system was engineered into a versatile gene-editing tool enabling manipulation of protospacer adjacent motif (PAM) downstream DNA. CRISPR-Cas9 genome editing system consists of two components: a “guide” RNA (gRNA) and a non-specific CRISPR-associated endonuclease (Cas9). The Cas9 protein is an endonuclease that uses guide RNA molecule (gRNA) to form base pairs with DNA target sequences, enabling Cas9 to introduce a site-specific DSB in the DNA. The CRISPR-Cas9 system offers unprecedented advantages over the ZFN and TALEN strategies. Due to its simplicity and efficiency, CRISPR-Cas9 system has quickly become the go-to genome engineering tool for animal model construction, drug development, gene therapy, agricultural breeding and many other applications.

Based on our knowledge and years of experience in DNA technology, Synbio Technologies has developed CRISPR-Cas9 gene/genome editing platform. We offer a one-stop solution for CRISPR-Cas9 projects to achieve high genome editing efficiency, including CRISPR-Cas9 sgRNA design, CRISPR-Cas9 sgRNA library design and genome editing.