Increasing fetal hemoglobin (HbF) levels in adult red blood cells provides clinical benefit to patients with sickle cell disease and some forms of β-thalassemia.To identify potentially druggable HbF regulators in adult human erythroid cells, we employed a protein kinase domain–focused CRISPR-Cas9–based genetic screen with a newly optimized single-guide RNA scaffold. The screen uncovered the heme-regulated inhibitor HRI (also known as EIF2AK1), an erythroid-specific kinase that controls protein translation, as an HbF repressor. HRI depletion markedly increased HbF production in a specific manner and reduced sickling in cultured erythroid cells. Diminished expression of the HbF repressor BCL11A accounted in large part for the effects of HRI depletion. Taken together, these results suggest HRI as a potential therapeutic target for hemoglobinopathies.

Background: CALHM1 is an ion channel for which structural information is lacking. Results: CALHM1 has poor ion selectivity and a wide (ϳ14 Å) pore and is a hexamer, with monomers having four transmembrane domains with cytoplasmic termini. Conclusion: CALHM1 shares structural features with pannexins, connexins, and innexins. Significance: CALHMs, connexins, and pannexins/innexins are three structurally related protein families with shared and distinct functional properties.

Chromatin structure is tightly intertwined with transcription regulation. Here we compared the chromosomal architectures of fetal and adult human erythroblasts and found that, globally, chromatin structures and compartments A/B are highly similar at both developmental stages. At a finer scale, we detected distinct folding patterns at the developmentally controlled β-globin locus. Specifically, new fetal stage-specific contacts were uncovered between a region separating the fetal (γ) and adult (δ and β) globin genes (encompassing the and noncoding genes) and two distal chromosomal sites (HS5 and 3'HS1) that flank the locus. In contrast, in adult cells, the - region contacts the embryonic ε-globin gene, physically separating the fetal globin genes from the enhancer (locus control region [LCR]). Deletion of the region in adult cells alters contact landscapes in ways more closely resembling those of fetal cells, including increased LCR-γ-globin contacts. These changes are accompanied by strong increases in γ-globin transcription. Notably, the effects of removal on chromatin architecture and gene expression closely mimic those of deleting the fetal globin repressor BCL11A, implicating BCL11A in the function of the region. Our results uncover a new critical regulatory region as a potential target for therapeutic genome editing for hemoglobinopathies and highlight the power of chromosome conformation analysis in discovering new control elements.