Fig. 8. p67/p67 embryos are developmentally delayed and show defective receptor trafficking in the visceral yolk sac (A) Images of control and p67/p67 embryos at E10.5 and E14.5 show that p67 homozygotes are consistently smaller and developmentally delayed compared with littermates. (B,C) Dab2 localization in the VYS of E12.5 dab2^+/+ (B) and p67/p67 (C) embryos. Dab2 protein is more diffuse when only the p67 isoform is present. (D,E) Cubilin localization in the VYS of these same embryos. In the wild-type embryo (D), cubilin staining was strongest in the apical brush-border, but was also visible inside the cell in vesicles. In p67/p67 embryos (E), cubilin was concentrated on the apical surface, and only a few small vesicles inside the cell contained cubilin. (F) Model for Dab2 function in the transport of nutrients and morphogens in the VE and VYS. YSC, yolk sac cavity.