title: Molecular and cellular mechanisms of sperm-oocyte interactions opinions relative to in vitro fertilization (IVF).
abstract: One of the biggest prerequisites for pregnancy is the fertilization step, where a human haploid spermatozoon interacts and penetrates one haploid oocyte in order to produce the diploid zygote. Although fertilization is defined by the presence of two pronuclei and the extraction of the second polar body the process itself requires preparation of both gametes for fertilization to take place at a specific time. These preparations include a number of consecutive biochemical and molecular events with the help of specific molecules and with the consequential interaction between the two gametes. These events take place at three different levels and in a precise order, where the moving spermatozoon penetrates (a) the outer vestments of the oocyte, known as the cumulus cell layer; (b) the zona pellucida (ZP); where exocytosis of the acrosome contents take place and (c) direct interaction of the spermatozoon with the plasma membrane of the oocyte, which involves a firm adhesion of the head of the spermatozoon with the oocyte plasma membrane that culminates with the fusion of both sperm and oocyte membranes (Part I). After the above interactions, a cascade of molecular signal transductions is initiated which results in oocyte activation. Soon after the entry of the first spermatozoon into the oocyte and oocyte activation, the oocyte's coat (the ZP) and the oocyte's plasma membrane seem to change quickly in order to initiate a fast block to a second spermatozoon (Part II). Sometimes, two spermatozoa fuse with one oocyte, an incidence of 1%-2%, resulting in polyploid fetuses that account for up to 10%-20% of spontaneously aborted human conceptuses. The present review aims to focus on the first part of the human sperm and oocyte interactions, emphasizing the latest molecular and cellular mechanisms controlling this process.
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine Larisa, University of Thessaly, Larissa 41110, Greece. ganif@med.uth.gr.
authors: George
authors: G
authors: Anifandis
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine Larisa, University of Thessaly, Larissa 41110, Greece. pireaschristina@gmail.com.
authors: Christina
authors: C
authors: Messini
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine Larisa, University of Thessaly, Larissa 41110, Greece. kdafop@yahoo.com.
authors: Konstantinos
authors: K
authors: Dafopoulos
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine Larisa, University of Thessaly, Larissa 41110, Greece. sotirious@med.uth.gr.
authors: Sotiris
authors: S
authors: Sotiriou
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine Larisa, University of Thessaly, Larissa 41110, Greece. messinis@med.uth.gr.
authors: Ioannis
authors: I
authors: Messinis
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D004527:Egg Proteins / Q000378:metabolism; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D010063:Ovum / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000378:metabolism*; D015044:Zona Pellucida / Q000378:metabolism; D000072216:Zona Pellucida Glycoproteins
chemical_list: D004527:Egg Proteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins; D051722:ADAM Proteins; C499566:ADAM3A protein, human