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The sperm of most vertebrates and invertebrates are surrounded by a primary egg envelope (the zone pellucida in mammals and vitelline envelope in amphibians and echinoderms, among others). We now understand a great deal about the major glycoproteins in the envelope and their function in gamete interactions, to the extent that inhibitors of the functions of these molecules are being tested as contraceptives in humans. Less is understood, however, about the coats that surround the primary envelopes (the cumulus layer in mammals and jelly coats in many other model systems). Our laboratory uses the anuran, Lepidobatrachus laevis, a newer amphibian model system, to study mechanics of fertilization. One goal is to isolate and purify the glycoproteins of the jelly coat. Using this information we will determine which of the glycoproteins may be significant in fertilization. Another is to isolate and identify the major glycoproteins of the vitelline envelope homologous to mammalian ZPA, ZPB and ZPC (also know as ZP1, ZP2 and ZP3). ZPC has already been identified in Lepidobatrachus and the primary sequence determined in this laboratory. Additionally, other processes involved in fertilization are less well understood, particularly mechanisms of final binding of sperm to receptors on the egg itself and the characterization, both cellular and molecular, of proteins and glycoproteins involved. We are also studying the sperm of this species. It has several unique features; it contains a double axoneme and an unusual accessory cell which is thought to be significant in the sperm's motility dynamics during fertilization.
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