PAPD5 silencing restores defective hematopoiesis in DKC1_A353V cells. (A) Colony-forming cell (CFC) potential of primitive hematopoietic progenitors in WT, WT_shEXOSC3, and WT_shPAPD5 cells from day 11 of IWP2-derived specification. (B) CFC potential of definitive hematopoietic progenitors in WT, WT_shEXOSC3, and WT_shPAPD5 cells from day 8 sorted CD34⁺CD43⁻ populations, as described in supplemental Figure 3A. (C) Representative flow cytometric analysis of CD34 and CD43 expression on day 11 of differentiation, following IWP2 treatment in WT, DKC1_A353V, DKC1_A353V_shEXOSC3, and DKC1_A353V_shPAPD5 cells. (D) Quantification of CD43⁺ population obtained from day 11 differentiation cultures treated with IWP2, as in panel C. (E) Primitive CFC potential in day 11 differentiation cultures, as in panel C. (F) Representative flow cytometric analysis of CD34 and CD43 expression on day 8 of definitive differentiation, following CHIR99021 and SB-431542 treatment in WT, DKC1_A353V, DKC1_A353V_shEXOSC3, and DKC1_A353V_shPAPD5 cells. (G) Quantification of CD34⁺CD43⁻ population obtained from day 8 differentiation cultures treated with CHIR99021 and SB-431542, as in panel F. (H) CFC potential of definitive hematopoietic progenitors, generated as shown in supplemental Figure 3A. (I) T-cell potential of CD34⁺CD43⁻ populations derived from WT, DKC1_A353V, DKC1_A353V_shEXOSC3, and DKC1_A353V_shPAPD5, obtained following CHIR99021 and SB-431542 treatment. (J) Relative abundance of oligoadenylated reads at mature 3′ end of TERC in WT, DKC1_A353V, DKC1_A353V_shEXOSC3, and DKC1_A353V_shPAPD5 hESC. n = 2. (K) Relative abundance of nonadenylated reads at mature 3′ end of TERC as in panel J. All experiments were conducted using n = 3, mean ± standard error of the mean, *P ≤ .05, unless otherwise indicated. Statistical analysis was performed using 1-way analysis of variance followed by Tukey’s post hoc test or Student t test (J-K). In red, population of interest. In all panels, LP denotes late passage (passage number >55).