Initial attempts to engineer genomes used homologous recombination (the cell’s natural high fidelity DNA repair mechanism) and revolved around the generation of transgenic mice using plasmid-based techniques in embryonic stem cells. This approach, while acceptable for transgenic mice, isn’t effective for the development of somatic cell lines due to the very low rates of homologous recombination in these cells. Instead, the process needs to be stimulated or an alternative approach used.
Horizon’s historical approach has been to take advantage of rAAV’s natural ability to amplify the basal levels of homologous recombination by 1,000X to 10,000X. Using its proprietary rAAV technology, Horizon has developed methods that further improve on this targeting efficiency.
An alternative method for stimulating genetic changes involves the use of nucleases to create a double-stranded DNA break at specific locations, then influencing the natural repair processes used to fix the break. Examples of this approach include use of Zinc Finger Nucleases (ZFN), Transcription Activator-Like Effector Nucleases (TALENs), and the CRISPR (Cas9) system.
Each of these approaches has its own features and strengths. While they share some similarities, they differ principally in the mechanism used to drive genetic modifications and it is these key differences are that make each best suited for addressing specific gene-editing challenges. Horizon Discovery has recently added ZFNs and CRISPR to its GENESIS™ genome editing platform, perfectly complementing its proprietary rAAV-based gene editing capabilities, and further supporting the company’s ability to generate virtually any genomic modification upon customer request.