Base-editing-mediated dissection of a γ-globin cis-regulatory element for the therapeutic reactivation of fetal hemoglobin expression
Panagiotis Antoniou, Giulia Hardouin, Pierre Martinucci, Giacomo Frati, Tristan Félix, Anne Chalumeau, Letizia Fontana, Jeanne Martin, Cécile Masson, Mégane Brusson, Giulia Maule, Marion Rosello, Carine Giovannangeli, Vincent Abramowski, Jean‐Pierre de Villartay, Jean‐Paul Concordet, Filippo Del Bene, Wassim El Nemer, Mario Amendola, Marina Cavazzana, Anna Cereseto, Oriana Romano, Annarita Miccio
Abstract
Sickle cell disease and β-thalassemia affect the production of the adult β-hemoglobin chain. The clinical severity is lessened by mutations that cause fetal γ-globin expression in adult life (i.e., the hereditary persistence of fetal hemoglobin). Mutations clustering ~200 nucleotides upstream of the HBG transcriptional start sites either reduce binding of the LRF repressor or recruit the KLF1 activator. Here, we use base editing to generate a variety of mutations in the -200 region of the HBG promoters, including potent combinations of four to eight γ-globin-inducing mutations. Editing of patient hematopoietic stem/progenitor cells is safe, leads to fetal hemoglobin reactivation and rescues the pathological phenotype. Creation of a KLF1 activator binding site is the most potent strategy - even in long-term repopulating hematopoietic stem/progenitor cells. Compared with a Cas9-nuclease approach, base editing avoids the generation of insertions, deletions and large genomic rearrangements and results in higher γ-globin levels. Our results demonstrate that base editing of HBG promoters is a safe, universal strategy for treating β-hemoglobinopathies.