Analyses of nonhematopoietic embryogenesis.

Whole E12.5 embryos and sections were stained with anti–PECAM-1 antibody. The morphology of the blood vessels (stained purple) in the lateral sides of somites (A-D, upside is dorsal) and fetal livers (E-H, arrowheads) of wild-type, transgenic (Tg), EpoR-null, and rescued embryos were compared. No differences were found among the embryos. In the embryonic heart sections (I-L), the smooth muscles of the left ventricles were stained with anti–alpha sarcomeric muscle actin antibody. Although the compact layer (between the arrowheads) of the rescued embryo (L) was normal, the compact layer of theEpoR^−/−embryo (K) was considerably thinner than that of wild-type (I) and transgenic (J) embryos. (M) A section including the heart (Ht) and liver (Li) of a Rescued-A embryo was stained with anti-GFP antibody. GFP⁺ cells were not detected in the heart, but most of cells in the liver were GFP⁺, as seen by the purple staining. Scale bar, 50 μm (E-H) and 200 μm (I-M).