Base Editing as a Therapeutic Strategy for Autosomal Dominant Tubulointerstitial Kidney Disease caused by Pathogenic UMOD Variants
Autosomal dominant tubulointerstitial kidney disease caused by pathogenic UMOD variants (ADTKD-UMOD) is an untreatable monogenic kidney disease in which misfolded uromodulin is retained in the endoplasmic reticulum and exerts a toxic gain-of-function effect. Here we systematically evaluate the full spectrum of base editing strategies targeting the UMOD locus. Base editors corrected a representative missense patient variant, p.Cys170Tyr, with A-to-G conversion efficiencies of up to 83.4%, restoring uromodulin trafficking to the plasmamembrane in cell lines and in human 3D kidney tubuloids. Mutation-agnostic inactivation wasachieved by four routes: premature stop codon introduction, splice-site disruption, allele-specific stop codon introduction and promoter attenuation. Maximum on-target efficienciesranged from 44.1% to 71.9%, providing a strategy set applicable across the UMOD allelicspectrum. Endogenous UMOD expression is rarely recapitulated in human cell models,leaving strategies that act on the endogenous gene difficult to assess in patient cells. Wetherefore established CRISPR activation (CRISPRa) of the endogenous UMOD promoterand confirmed its ability to upregulate UMOD expression in human urine-derived cells. Thisapproach further enabled quantification of endogenous UMOD transcript reduction followingbase editing in HEK293 cells. These results establish base editing as a versatile approachfor ADTKD-UMOD and provide a primary human system for testing interventions targetingendogenous UMOD expression, from nucleic acid-based silencing to small molecules.