Rescue of hematopoietic cells from apoptotic cell death by transgenic expression of EpoR in E12.5 embryonic livers.

(A-D) Sections of E12.5 embryonic livers were stained with anti-GFP antibody. GFP⁺ cells (stained purple) are expected to coexpress the EpoR transgene. Megakaryocytes (arrowheads) and erythroid cells were stained positive in Tg-A (B) and Rescued-A (D) embryos only. (E-H) TUNEL (terminal transferase-mediated dUTP nick-end labeling) assay of E12.5 embryonic liver cells. Nuclei of TUNEL-positive cells were stained purple (arrows). Although most cells in the EpoR^−/−liver stained TUNEL positive (G), livers of the rescued (H), wild-type (E), and Tg-A (F) embryos contained only a small number of positive cells. Scale bar equals 50 μm (A-H). (I) TUNEL-positive cells as a percentage of the total liver cells counted in each section. (J) Number of PI-negative cells assessed by FACS analysis.