IFN-α only inhibits terminal differentiation in HC-derived cells and induces apoptosis in PV-derived cells. (A) Analysis of cell cycle regulation from scRNA-seq data. The absolute (top) and relative (bottom) numbers of cells are shown in the different erythroid maturation stages. Blue indicates G1 phase; red indicates G2M phase; green indicates S phase. Samples were grouped by treatment and diagnosis. (B) CD34⁺ cells isolated from blood were used in an in vitro differentiation model. Maturation was analyzed using flow cytometry. Erythrocytic cells that no longer expressed CD71 but still expressed CD235a were counted as mature erythrocytes. Statistical analysis was done using paired t tests after passing the Shapiro-Wilk test for normality. (C) The hallmark apoptosis pathway was analyzed from the scRNA-seq data in different cell types grouped by treatment and PV or HC. Two examples of violin plots in MEPs and reticulocytes are shown on the left. The heat map on the right summarizes the results for all cell types. (D) PBMCs were seeded in CFU assays and stimulated with 1000 U/mL IFN-α on day 8 to 12. Cells were grouped by erythroid maturation stages by first excluding all CD45⁺ cells and subsequently grouping the cells into CD71⁺CD235a⁺ (immature) and CD71⁻CD2354a⁺ (mature) populations. The FC in apoptosis was compared among the different groups, and induction was statistically analyzed using a one-sample t test. (E) Most and least apoptotic quantile of cells (PV-derived MEPs, ProE, and BasoE combined) from the scRNA-seq data were compared and DEGs were derived. The gene ontology terms were derived from DEGs, and the 5 most up- or downregulated pathways are shown. ns, not significant; ∗P <. 05; ∗∗ P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001.