Topical Eyedrop of 4-Hydroxytamoxifen Enables Cre-Mediated Gene Editing in Oligodendrocytes

Inducible CreERT-mediated gene editing is a powerful tool for targeted gene manipulation, but systemic tamoxifen (Tam) administration can cause off-target effects and toxicity. Here we demonstrate that topical administration of 4-hydroxytamoxifen (4-OHT) eye drops in Plp1-CreERT/tdTomatof/f mice effectively induces CreERT-mediated recombination specifically in oligodendrocytes of the optic nerve, optic chiasm, and adjacent CNS regions including the optic tract, hippocampus, and corpus callosum. This localized approach achieves robust tdTomato expression in over 80% of oligodendrocytes without detectable retinal structural or functional abnormalities, as confirmed by electroretinography and fundus imaging. These findings demonstrate a safe, non-invasive method for spatially restricted gene editing in the visual pathway and certain brain areas, providing a valuable platform for investigating oligodendrocyte biology and demyelinating diseases while minimizing systemic side effects associated with Tam treatment.