About this Research Topic
Eggs and sperm are terminally differentiated haploid cells, with features specifically developed to ensure they can meet, bind and fuse with one another. Gametes’ morphology varies from species to species and is perfectly adapted to the environment where fertilization takes place. In most species sperm are motile cells, propelled towards the eggs by the wave-like motion of their tails, while eggs are immotile and usually protected by an extracellular layer of glycoproteic material.
The sperm-egg interaction encompasses two fundamental events: firstly the sperm-egg binding, and secondly the fusion of their cell membranes. Binding refers to the interaction of the sperm with the egg’s extracellular vestments as well as to its interaction with the egg’s cell membrane. Eventually cell fusion merges the sperm and the egg into a novel single unit, which deploys a variety of changes to prevent multiple fusion events. This strategy is common amongst all species in which polyspermy generates non-viable embryos.
Over the past two decades, few proteins deemed essential for fertilization have been identified; nonetheless, the precise mechanism of sperm-egg binding and fusion remains elusive. For most species, we only have a fragmented knowledge of the whole process, and it is remarkable that basic information like the identity of the molecules involved is still missing. The lack of understanding of this fundamental biological process has hampered the creation of better and more varied contraceptive methods, while the development of assays and screenings aimed at improving the assisted reproductive technology is lagging behind.
In this Research Topic, we aim to shed light on all steps of sperm-egg interaction, and to provide a space where researchers can present their investigations, discuss and propose innovations to advance the field. The collection is open to articles covering fertilization in all species, vertebrates and invertebrates, from model organisms to endangered species. We welcome Original Research, Methods, Review, Mini-Review, Brief Research Report, and Perspective articles.
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