Polymerization of a vitelline envelope (VE)-like structure produced by using fractionated VE extracts from carp eggs

Fractionation of vitelline envelope (VE) extracts from carp eggs made possi ble the efficient polymerization of a VE-like structure. The structure corr esponded to the fourth layer of the VE or fertilization envelope (FE), and its organization was achieved by reassembly in vitro after solubilization o f the sheets composed of filamentous substances or network-like aggregates which were induced by a cortical alveolus sialoglycoprotein or thrombin. Th e sialoglycoprotein was a serine proteinase and immunolocalized only in the structure at the periphery of cortical alveoli, not in the VE and yolk gra nules. Ultrastructural features of the VE-like structure suggested that rea ssembly in vitro occurred via several intermediates in the process of polym erization. A polyclonal antibody produced against one of the assembled VE c omponents, a 64 kDa protein, more intensely immunostained the outer periphe ry of the VEs than other areas, and immunoelectron microscopy showed that i mmunogold particles specifically labeled reassembled VE-like structures and major skeletons of the networks or network-like sheets. The protein with a molecular weight of 64 kDa was found to be a DNase. Thus, these results su ggest a new approach to investigating not only the FE assembly process in v itro but also the organizing relationship between the major skeleton of the VE or FE and other additional constituents. J. Exp. Zool. 286:755-766, 200 0. (C) 2000 Wiley-Liss, Inc.