Epithelial‐cadherin (E‐cadherin) is a member of a family of Ca2+‐dependent cell adhesion molecules which are localized in zonulae adherens and play an important role during development. E‐cadherin is abundant in rat embryos and their yolk sacs during organogenesis. The phorbol ester, 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA), has been reported to disrupt the morphology and functional development of the rat embryonic visceral yolk sac. The present study investigated the possibility that the effect of TPA on yolk sac development may be due to the altered expression of E‐cadherin. Rat embryos, with their yolk sacs intact, were cultured on day 10 of gestation for 1 hr. At this time the vehicle, dimethyl sulfoxide (DMSO), or TPA (at different concentration) was added to the culture medium; the cultures were continued for up to 24 hr. Embryos and yolk sacs were collected separately at the end of each culture period. The relative abundances of E‐cadherin mRNA and protein were analyzed with Northern and Western blot analyses. Despite the TPA‐induced abnormalities in yolk sac development, the relative abundance of E‐cadherin mRNA or protein in the yolk sac was not altered by TPA exposure. However, in embryos exposed to dysmorphogenic concentration of TPA, the relative abundance of E‐cadherin mRNA was significantly increased after 24 hr in culture, compared to either controls or embryos exposed to non‐dysmorphogenic concentration of TPA. The magnitude of the increase in embryonic E‐cadherin mRNA appeared to correlate with the severity of the embryo malformations. Interestingly, despite this increase in embryonic E‐cadherin mRNA abundance, no increase in E‐cadherin protein concentrations was found in the embryo. The timing of the increased relative abundance of E‐cadherin mRNA in TPA‐exposed malformed would suggest an indirect relationship with the embryo malformations observed. Activation of protein kinase C is likely to be involved in both the embryotoxic effects of TPA and the induction of increased concentrations of E‐cadherin mRNA in the embryo since 4α‐phorbol‐12,13‐didecanoate (4α‐PDD), a phorbol ester analog which does not activate protein kinase C, had no effect. This study demonstrates that TPA‐induced embryo malformations are associated with an increased abundance of E‐cadherin mRNA in the embryo, but not in the yolk sac, and that these action of TPA depend on the activation of protein kinase C. © 1994 Wiley‐Liss, Inc.
ASJC Scopus subject areas
- Developmental Biology
- Health, Toxicology and Mutagenesis