Exosc3 expression in the hematopoietic system confers erythroid progenitor activity in an erythroid cell–intrinsic manner. (A) Exosc3 ablation did not affect cellular viability, assessed by DAPI staining. (B) GFP⁺ percentage of live fetal liver cells. Significance by Tukey multiple comparisons test. (C) GFP⁺ percentage from live R1 cells parent gate. Significance by Tukey multiple comparisons test. (D) Representative flow cytometric plots depicting erythroid maturation based on CD71 and Ter119 expression in Exosc3^C/C Cre⁻ and Exosc3^C/C Cre⁺ E14.5 embryos (13 independent experiments: Exosc3^C/C Cre⁻ = 21 and Exosc3^C/C Cre⁺ = 17). (E) Quantification of R1 to R4 populations from E14.5 fetal livers. (F) Experimental scheme for assessing CFU activity of Exosc3^C/C Cre⁻ and Exosc3^C/C Cre⁺ of sorted GFP⁺ R1 + R2 from E12.5 or E14.5 fetal livers. Colonies were quantified after 3 days (CFU-E) or 8 days (BFU-E and CFU-GM) in methylcellulose. (G) CFU activity of Exosc3^C/C Cre⁻ and Exosc3^C/C Cre⁺ 3000 sorted GFP⁺ R1 + R2 cells from E12.5 fetal livers (7 independent experiments: Exosc3^C/C Cre⁻ = 7 and Exosc3^C/C Cre⁺ = 6). (H) CFU activity of Exosc3^C/C Cre⁻ and Exosc3^C/C Cre⁺ with 5000 sorted GFP⁺ R1 + R2 from E14.5 fetal livers (7 independent experiments: Exosc3^C/C Cre⁻ = 9 and Exosc3^C/C Cre⁺ = 6). Quantitative data are presented as box and whisker plots, with bounds from the 25th to 75th percentiles, the median line, and whiskers ranging from minimum to maximum values. ∗P < .05, ∗∗P < .01, and ∗∗∗P < .001, by unpaired t test. APC, allophycocyanin.