Fluorescent Endogenous Tagging with a Covalent Hook (FETCH) labels cell surface proteins (CSPs) in vivo through a stable covalent bond mediated by the DogTag-DogCatcher peptide partner system. In FETCH, DogTag is introduced into extracellular loops of CSPs through genome engineering, enabling covalent bond formation with a genetically encoded DogCatcher-GFP fusion protein that can be secreted from a variety of cell types in intact animals.

Cell surface proteins of interest are labeled with the DogTag peptide on their extracellular domain. The GFP-labeled DogCatcher is secreted and fuses covalently to the DogTag peptide.

See Rostam et al. 2025 for more details: doi.org/10.1073/pnas.2503166122