Characterization, fate, and function of hamster cortical granule components

Abstract

Little is known about the composition and function of mammalian cortical granules. In this study, lectins were used as tools to: (1) estimate the number and molecular weight of glycoconjugates in hamster cortical granules and show what sugars are associated with each glycoconjugate; (2) identify cortical granule components that remain associated with the oolemma, cortical granule envelope, and/or zona pellucida of fertilized oocytes and preimplantation embryos; and (3) examine the role of cortical granule glycoconjugates in preimplantation embryogenesis. Microscopic examination of unfertilized oocytes revealed that the lectins PNA, DBA, WGA, RCA120, Con A, and LCA bound to hamster cortical granules. Moreover, LCA and Con A labeled the zona pellucida, cortical granule envelope, and plasma membrane of fertilized and artificially activated oocytes and two and eight cell embryos. Lectin blots of unfertilized oocytes had at least 12 glycoconjugates that were recognized by one or more lectins. Nine of these glycoconjugates are found in the cortical granule envelope and/or are associated with the zona pellucida and plasma membrane following fertilization. In vivo functional studies showed that the binding of Con A to one or more mannosylated cortical granule components inhibited blastomere cleavage in two-cell embryos. Our data show that hamster cortical granules contain approximately 12 glycoconjugates of which nine remain associated extracellularly with the fertilized oocyte after the cortical reaction and that one or more play a role in regulating cleavage divisions. © 2001 Wiley-Liss, Inc.