Carbohydrate-mediated sperm-egg interaction and species specificity: A clue from the Unio elongatulus model

As a first step fertilization requires that sperm bind to the extracellular coat of the egg. It is generally accepted that binding is mediated by comp lex carbohydrates on the egg coat, recognized by carbohydrate-binding prote ins on the sperm surface. In the mollusc bivalve Unio elongatulus, the main functional epitope of the carbohydrate ligand has been determined, and it shares several characteristics with other sugar structures involved in the fertilization process in different animal models. A polyclonal antibody aga inst the Unio epitope reacts with the human ZP3 glycoprotein and the Unio l igand binds human spermatozoa in an in vitro assay. These findings are disc ussed in the light of the species specificity of sperm-egg binding at ferti lization. Copyright (C) 2001 S. Karger AG, Basel.