Not Just for Manufacturing
The value of cell-line optimization is not limited to biomanufacturing. For example Cellectis is involved in improving cells for research and gene therapy as well as production. The company’s lead technology is based on meganucleases, or “DNA scissors” that selectively remove genes. Meganucleases have been used for at least 25 years, but Cellectis claims to have engineered these enzymes for greater specificity.
Meganucleases, which are found primarily in single-celled organisms, algae, and some plant organelles, cut chromosomes at specific locations. Despite their relative rarity in nature, meganucleases may be inserted into numerous cell types, where they dependably “cut-and-paste” at target sequences provided the genome contains a specific, 12–30 base pair target sequence. Long recognition sequences are the key to the enzymes’ specificity. If the sequence does not exist naturally it must first be introduced, which has been the major limitation of natural meganucleases.
Cellectis has discovered how to adapt these enzymes to a much broader range of DNA sequences by modifying the meganuclease recognition capability and selecting specific enzymes through high-throughput screening.
The company has thus far worked on workhorse mammalian cells such as HEK293 (human), NIH333 (mouse), and CHO-k1 (hamster), which together cover major areas of interest to both researchers and biomanufacturers. “Clients use our products mostly for drug screening, protein production, and functional genomics,” explains Marc Le Bozec, CEO. Cellectis has enjoyed a “100 percent success rate,” according to Le Bozec, in deleting and inserting genes to produce stable clones.
Cellectis sells kits known as meganuclease recombination systems consisting of specific meganucleases paired with a target DNA template sequence. Users, says Le Bozec, have been 80% successful in targeting specific sites on the genome for gene deletion, insertion, or replacement.
“Each kit provides ten experiments, of which eight should produce a stable, desired clone within four weeks. Moreover it will generate a single copy of a single gene precisely where the customer desires it.” This provides the opportunity, for example, to quantify the activity of two genes located in the same genetic environment. “You can now compare apples to apples,” Le Bozec explains.
By the end of the year the company hopes to introduce kits for knocking down genes by insertion of siRNA. It is planning a next-generation product in 2011 for gene knockout.