The presence of heparan sulfate in the mammalian oocyte provides a clue to human sperm nuclear decondensation in vivo

BACKGROUND: Previous results from our laboratory have led us to proposeheparan sulfate (HS) as a putative protamine acceptor duringhuman sperm decondensation in vivo. The aim of this paper wasto investigate the presence of glycosaminoglycans in the mammalianoocyte in an effort to better support this contention. METHODS: Two experimental approaches are used: oocyte labeling to identifythe presence of HS and analysis of sperm decondensing abilityof fresh oocytes in the presence or absence of specific glycosidases. RESULTS: Staining of mouse zona-intact oocytes with the fluorescent cationicdye, Rubipy, at pH 1.5 allowed for the detection of sulfateresidues in the ooplasm by confocal microscopy. HS was detectedin the ooplasm by immunocytochemistry. A sperm decondensationmicroassay using heparin and glutathione was successfully developed.The same level of sperm decondensation could be attained whenheparin was replaced by mouse zona-free oocytes. Addition ofheparinase to the oocyte/glutathione mixture significantly reducedsperm decondensation (P = 0.0159), while there was no effectfollowing addition of either chondroitinase ABC or hyaluronidase. CONCLUSIONS: The results presented in this paper demonstrate for the firsttime that HS is present in the mammalian oocyte and show thatHS is necessary for fresh oocytes to express their sperm decondensingability in vitro.