Domain-focused CRISPR-screen identifies HRI as a fetal hemoglobin regulator in human erythroid cells

Increasing fetal hemoglobin (HbF) levels in adult red blood cells provides clinical benefit to patients with sickle cell disease and some forms of beta-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 sgRNA 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.

在成人红细胞中升高胎儿血红蛋白（fetal hemoglobin, HbF）水平，可为镰状细胞病（sickle cell disease）与部分类型β地中海贫血（beta-thalassemia）患者带来临床获益。为鉴定成人红系细胞中潜在可药用的HbF调控因子，我们采用了聚焦蛋白激酶结构域的CRISPR/Cas9遗传筛选，并使用了全新优化的单向导RNA（single-guide RNA, sgRNA）支架。该筛选发现血红素调控抑制剂（heme-regulated inhibitor, HRI），亦称EIF2AK1——一种调控蛋白质翻译的红系特异性激酶——是HbF的阻遏物。敲低HRI可通过特异性方式显著提升HbF的产生量，并减轻培养红系细胞的镰变程度。HbF阻遏物BCL11A的表达下调，在很大程度上解释了HRI敲低所产生的效应。综上，本研究结果提示HRI可作为血红蛋白病（hemoglobinopathies）的潜在治疗靶点。