Resistance to modulation of in vivo gene expression by genomic editing

EKLF/KLF1, a master erythroid transcription factor, is an attractive target because haploinsufficiency is benign and associated with hereditary persistence of fetal hemoglobin (HPFH). Here we test whether enhancer disruption can recapitulate this state by targeting two KLF1 regulatory elements, EHS1 and INT1.

EHS1 editing reduces KLF1 expression and increases γ-globin, and combined INT1/EHS1 targeting produces additional increases in some samples, although responses are variable. In xenotransplantation models, edited cells engraft and retain indels but fail to sustain consistent γ-globin induction. Epigenetic profiling across the KLF1 genetic locus reveals a remarkable resistance to loss of hypersensitive sites.