Vertebrate eggs are surrounded by an extracellular matrix with similar functions and conserved individual components: the zona pellucida (ZP) glycoproteins. In mammals, chickens, frogs, and some fish species, we established an updated list of the ZP genes, studied the relationships within the ZP gene family using phylogenetic analysis, and identified ZP pseudogenes. Our study confirmed the classification of ZP genes in six subfamilies: ZPA/ZP2, ZPB/ZP4, ZPC/ZP3, ZP1, ZPAX, and ZPD. The identification of a Zpb pseudogene in the mouse genome, Zp1 pseudogenes in the dog and bovine genomes, and Zpax pseudogenes in the human, chimpanzee, macaque, and bovine genomes showed that the evolution of ZP genes mainly occurs by death of genes. Our study revealed that the extracellular matrix surrounding vertebrate eggs contains three to at least six ZP glycoproteins. Mammals can be classified in three categories. In the mouse, the ZP is composed of three ZP proteins (ZPA/ZP2, ZPC/ZP3, and ZP1). In dog, cattle and, putatively, pig, cat, and rabbit, the zona is composed of three ZP proteins (ZPA/ZP2, ZPB/ZP4, and ZPC/ZP3). In human, chimpanzee, macaque, and rat, the ZP is composed of four ZP proteins (ZPA/ZP2, ZPB/ZP4, ZPC/ZP3, and ZP1). Our review provides new directions to investigate the molecular basis of sperm-egg recognition, a mechanism which is not yet elucidated.

Equine oocyte competence after in vitro maturation (IVM) was investigated in terms of the diameter of the follicle of origin and the stage of the estrous cycle, with three criteria of maturation: nuclear stage after DNA Hoechst staining, meiotic spindle morphology after tubulin immunocytochemical staining, and cortical granule localization after lectin labeling. Seven successive in vivo ultrasound-guided follicular punctures were performed on 10 cyclic saddle mares, alternatively at the end of the follicular phase (after induction of ovulation with a gonadotropin injection) and in midluteal phase (with or without a gonadotropin injection). Expanded cumulus-oocyte complexes (COCs) were stained at collection, and compact COCs were stained after in vitro culture. They were observed under a confocal microscope. Successive punctures on one mare provided 0.9 preovulatory COCs and 8 immature COCs per 22 days. Among the preovulatory oocytes, 55% had completed nuclear and cytoplasmic maturation, 86% of which displayed a normal meiotic spindle. Of the 262 oocytes cultured in vitro, 37% completed nuclear maturation. The nuclear and cytoplasmic maturation rate significantly increased with follicle diameter. The IVM rate tended to be higher in follicular phase and tended to increase in luteal phase with the gonadotropin injection. The meiotic spindle morphology was not significantly different between the classes of follicular diameters. This study provided the opportunity to increase the number of characterized oocytes collected per cycle and per mare. This is the first report showing the progressive acquisition of meiotic competence in the equine oocyte during antral follicle growth and is the only description of the equine meiotic spindle.

Interleukins (ILs) are known best for their involvement in the immune system and their role during inflammation. In the ovary, a growing body of evidence suggests that the ovarian follicle is a site of inflammatory reactions. Thus ovarian cells could represent sources and targets of ILs. Since then, the IL-1 system components (IL-1 , IL-1 , IL-1 receptor antagonist, IL-1 receptors) have been demonstrated to have several sites of synthesis in the ovary. These factors have been localized in the various ovarian cell types, such as the oocyte, granulosa and theca cells, in several mammalian species. IL-1-like bioactivity has been reported in human and porcine follicular fluid at the time of ovulation. The role of IL-1 in local processes is still poorly known, although there is evidence for involvement in the ovulation process, and in oocyte maturation. More precisely, IL-1 may be involved in several ovulationassociated events such as the synthesis of proteases, regulation of plasminogen activator activity, prostaglandin and nitric oxide production. IL-1 also regulates ovarian steroidogenesis. These different aspects of the involvement of the IL-1 system in important aspects of female reproduction are discussed.