Zinc finger nucleases (ZFNs) are a class of engineered DNA-binding proteins that facilitate highly specific targeted genomic editing by creating double-stranded breaks in DNA at user specific locations. “You can use ZFN technology to create your choice of stable, genetically engineered cell lines or organisms harboring gene deletions, additions, or other modifications with exquisite specificity,” says Greg Davis, Ph.D., principal R&D scientist for ZFN technology at Sigma-Aldrich.
The company is focusing a segment of their business on providing ZFN products and ZFN custom services. They became the exclusive licensee and distributor of such research reagents under an agreement established in 2007 with Sangamo Biosciences.
According to Dr. Davis, slicing both strands is important for site-specific mutagenesis applications because the break stimulates the cell’s natural DNA-repair processes, i.e., homologous recombination and nonhomologous end joining (NHEJ). Harnessing nature’s toolbox for repair allows generation of precisely targeted in vitro or in vivo genomic editing with targeted gene deletions (knockouts), integrations, or other modifications.
“Via the NHEJ pathway, ZFNs have enabled creation of knockout cells and animals at high frequency without the need for drug selection or exogenous DNA templates. This has greatly reduced timelines for isolating modified cells and animals,” he explains.
Using the technology, the company has created knockout and SNP insertion cell lines in their oncology and breast cancer panels. Additionally, the Pathway and Cytoskeletal Marker cell lines comprise a suite of genes tagged at the endogenous locus that allow an investigator to monitor protein expression and localization.
A large part of Sigma’s ZFN technology is devoted to custom service for its clients. Kevin Kayser, Ph.D., director of the CHOZN® platform for SAFC, notes, “Not everyone wants to be a gene-editing expert. Sometimes it is more efficient to outsource that. We provide off-the-shelf specific ZFNs to target genes for human, mouse, and rat studies in the form of cell lines and animals.”
SAFC has taken the ZFN technology a step further by utilizing it to create CHO cell lines for use in biopharmaceutical applications. “These CHOZN cell lines were purpose built to enable biopharmaceutical producers to advance their molecules in the clinic faster, while adhering to their stringent regulatory expectations,” says Dr. Kayser.
SAFC currently provides both glutamine synthetase and dihydrofolate reductase knockout CHO cell lines to biopharmaceutical customers, as they represent the two most commonly used metabolic selection systems in the industry, according to Dr. Kayser.