Quickfreeze, deepetch, rotaryshadow views of the extracellular matrix and cortical cytoskeleton of Xenopus laevis eggs

The quickfreeze, deepetch, rotaryshadow technique provides a powerful tool to study the structural dynamics of extracellular matrices. Using this technique, we show that the extracellular investments of the Xenopus laevis egg are multilayered and securely anchored to the egg surface. The cortical cytoskeleton within the egg contains embedded cortical granules with surrounding endoplasmic reticulum and is capped by a thin reticular sheet that contacts the inner surface of the plasma membrane. The extracellular matrix undergoes three distinct changes at fertilization: (a) formation of asmoothlayer below the vitelline envelope (VE), (b) transformation of the VE itself to an altered VE composed of concentric fibrous sheets, and (c) formation of a dense,briarpatchlike fertilization layer at the upper surface of the VE. Copyright1989 WileyLiss, Inc.