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Inhibition of bovine sperm‐oocyte fusion by the carbohydrate GalNAc
Author(s) -
Gougoulidis Tiki,
Trounson Alan,
Dowsing Aneta
Publication year - 1999
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(199910)54:2<179::aid-mrd10>3.0.co;2-j
Subject(s) - human fertilization , biology , sperm , oocyte , lectin , fructose , carbohydrate , andrology , biochemistry , microbiology and biotechnology , botany , genetics , embryo , medicine
The TEC‐2 epitope is a carbohydrate located on the plasma membrane (oolemma) of the oocyte and appears to be involved in bovine sperm‐oolemma fusion. The carbohydrates N‐acetylgalactosamine (GalNAc) and galactose are part of the TEC‐2 epitope and this study investigated the involvement of these carbohydrates during bovine fertilization. Gametes were exposed to the carbohydrates GalNAc, galactose, and fructose, and the lectins DBA and Con A to determine whether there was an effect on fertilization. The DBA lectin recognizes the carbohydrate GalNAc, whereas Con A recognizes the carbohydrates glucose and mannose. Oocytes pretreated with the DBA lectin prior to fertilization showed a reduction in cleavage corresponding to an increase in lectin concentrations. There was a significant increase in sperm‐oolemma binding although fusion was inhibited. Oocytes exposed to GalNAc prior to sperm insemination had no effect on fertilization, however, sperm pretreatment with the carbohydrate caused inhibition of fertilization, with a reduction in cleavage rates as the GalNAc concentration increased. There was also a significant decrease in sperm‐oolemma fusion and a significant increase in sperm‐oolemma binding. When gametes were exposed to GalNAc at the time of fertilization a similar response to that seen with sperm pretreatment was observed. The carbohydrates galactose and fructose and the lectin Con A did not affect fertilization. In conclusion, the carbohydrate GalNAc, which is associated with the TEC‐2 epitope, has a specific role during bovine sperm‐oolemma fusion. This study also suggests that there is a carbohydrate‐binding molecule on the sperm that binds GalNAc. Mol. Reprod. Dev. 54:179–185, 1999. © 1999 Wiley‐Liss, Inc.