Analyses of mEpoR^−/−, hEpoR⁺ embryos.

(A,B) The mEpoR^−/− pale embryo (A) at E12.5 contrasts with the erythroid-rich mEpoR^−/−, hEpoR⁺embryo (B). (C-H) The increased apoptotic activity (TUNEL-positive cells) in the mEpoR^−/− fetal liver (C), heart (E), and brain (G) is rescued by the hEpoR transgene, with reduced TUNEL-positive cells in the corresponding fetal liver (D), heart (F), and brain (H). The bar in (C) indicates 0.05 mm.