Anti-Her2 (trastuzumab) antibody-producing CHO DG44 cells (CHO-HER) were transfected with ZFNs or TALENs targeting GDP-fucose transporter using 4D Nucleofector (Lonza, Cologne, Germany) system according to manufacturer’s protocol. Briefly, 1.5 million cells were harvested from exponentially growing suspension culture and washed with Dulbecco’s phosphate buffered saline (DPBS) (Life Technologies). The cells were suspended in 100 µl of SG cell line Nucleofector solution containing 5 µg of plasmid DNA (2.5 µg for each ZFN or TALEN) in a Nucleocuvette. Electroporation was then carried out using a Lonza 4D-Nucleofector™ X unit. Following transfection, cells were incubated in suspension in a 3 ml CD CHO : HyClone PF CHO medium in a 6-well plate overnight before they were transferred into a 25 ml fresh medium in a 125-ml shake flask for further culture. Cells were then harvested for AAL-staining and FACS at 7-10 days post-transfection. For CRISPR-Cas9 modification, 5 million suspension CHO-K1 cells were electroporated using 4D-Nucleofector system with 5 µg of CRISPR-Cas9 plasmids in 100 µl of SG cell line Nucleofector solution. Following transfection, cells were recovered in growth medium in a suspension 6-well plate overnight before being scaled up to shake flask culture. Cells were then harvested for AAL-staining and FACS at 7-10 days post-transfection.