Toward identification of all modulators of erythropoiesis

The complete array of genes required for terminal erythroid differentiation remains unknown. To address this knowledge gap, we performed a genome-scale CRISPR knock-out screen in the human erythroid progenitor cell line HUDEP-2. We validated candidate regulators of erythroid differentiation in a custom secondary screen. Comparison of sgRNA abundance in the CRISPR library, proerythroblasts, and orthochromatic erythroblasts, resulted in the identification of genes that are essential for proerythroblast survival and genes that are required for terminal erythroid differentiation. Among the top genes identified were known regulators of erythropoiesis, underscoring the validity of this screen. Notably, using a Log2 fold change of <-1 and false discovery rate of <0.01, the screen identified 277 genes that are required for terminal erythroid differentiation, including multiple novel genes not previously nominated through GWAS. NHLRC2, which was previously implicated in hemolytic anemia, was a highly ranked gene. We suggest that anemia due to NHLRC2 mutation results at least in part from a defect in erythroid differentiation. Another highly ranked novel gene in the screen was VAC14, which was validated for its requirement in erythropoiesis in vitro and in vivo. Thus, data from this CRISPR screen may help classify the underlying mechanisms that contribute to erythroid disorders.