For gene modification projects, such as gene tagging, promoter swapping and nucleotide substitution, Cellectis bioresearch offers Custom TALEN™ Services. Those services include the production and validation of a Custom TALEN™ targeting any gene, at any position, in any genome.

All gene modification projects follow the same principle: the Custom TALEN™ binds its recognition site as close as possible to the site of modification, inducing a DSB. User-defined mutation can then be introduced by transfecting a plasmid whose sequence contains both a heterologous region with the user-defined mutation and regions homologous to the targeted genomic sequence.

The DSB is repaired by homologous recombination (HR) in presence of this plasmid; referred to as a Donor Matrix (for nucleotide substitution, gene tagging or modification).

DSB-stimulated HR at the TALEN™ recognition site gene tagging. The gene tag to be integrated is centered within the regions of homology.

DSB-stimulated HR at the TALEN™ recognition site enables nucleotide substitution. The substituted nucleotide is centered within the regions of homology. Silent mutations are introduced within the TAL Effector recognition sites present on the Donor Matrix, to prevent TALEN™ cleavage.