U-cadherin in Xenopus oogenesis and oocyte maturation.
U-cadherin is a member of the cadherin family in Xenopus that participates in interblastomere adhesion in the early embryo from the first cleavage onwards. Though a maternal pool of U-cadherin is available in the egg, it is not present on the egg membrane (Angres et al., 1991. Development 111, 829-844). To assess the origin of this unexpected distribution in the egg, the accumulation and localization of the cadherin during oogenesis and oocyte maturation were investigated. We report here that U-cadherin is present in Xenopus oocytes throughout oogenesis. It is localized at the oocyte-follicle cell contacts suggesting that it functions in the adhesion of the two cell types. When oocytes mature and the contacts to the follicle cells break, U-cadherin disappears from the oocyte surface. Evidence for a translocation of U-cadherin from the membrane to the inside of the oocyte was obtained when the fate of membrane-bound U-cadherin, which was labelled on the surface of oocytes prior to maturation, was followed through maturation. The total U-cadherin content of the oocyte increases during maturation. Metabolic labelling experiments indicate that at maturation the translation of U-cadherin is elevated well above the level that one would expect from the general increase in protein synthesis is presumably the main source of the maternal pool of U-cadherin in the egg.
Müller
A H
AH
Max-Planck-Institut für Entwicklungsbiologie, Tübingen, FRG.
Angres
B
B
Hausen
P
P
D000818:Animals; D015820:Cadherins / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology; D002454:Cell Differentiation; D005260:Female; D007365:Intercellular Junctions / Q000502:physiology; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D009866:Oogenesis / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology / Q000502:physiology; D014981:Xenopus
D015820:Cadherins