Precision genome editing: a small revolution for glycobiology.

Precise and stable gene editing in mammalian cell lines has until recently been hampered by the lack of efficient targeting methods. While different gene silencing strategies have had tremendous impact on many biological fields, they have generally not been applied with wide success in the field of glycobiology, primarily due to their low efficiencies, with resultant failure to impose substantial phenotypic consequences upon the final glycosylation products. Here, we review novel nuclease-based precision genome editing techniques enabling efficient and stable gene editing, including gene disruption, insertion, repair, modification and deletion. The nuclease-based techniques comprised of homing endonucleases, zinc finger nucleases, transcription activator-like effector nucleases, as well as the RNA-guided clustered regularly interspaced short palindromic repeat/Cas nuclease system, all function by introducing single or double-stranded breaks at a defined genomic sequence. We here compare and contrast the different techniques and summarize their current applications, highlighting cases from the field of glycobiology as well as pointing to future opportunities. The emerging potential of precision gene editing for the field is exemplified by applications to xenotransplantation; to probing O-glycoproteomes, including differential O-GalNAc glycoproteomes, to decipher the function of individual polypeptide GalNAc-transferases, as well as for engineering Chinese Hamster Ovary host cells for production of improved therapeutic biologics.