Figure 7.

Paracellular barrier assay of the Tjp1^+/+ and Tjp1^−/− yolk sac at E9.5. (A) Biotinylation from the outside of yolk sacs in Tjp1^+/+ and Tjp1^−/− embryos. Conjugated biotin was detected with avidin-Texas Red, which did not penetrate the paracellular barrier. (B) Biotinylation from the inside of yolk sac in Tjp1^+/+ and Tjp1^−/− embryos. When biotin was subcutaneously injected into the excoelomic cavity (*), it was spread beyond the extraembryonic mesodermal cell sheets, showing no barrier function in the extraembryonic mesoderm. Bar, 50 μm.