title: Morphological, cellular and molecular changes during postovulatory egg aging in mammals.
abstract: Postovulatory aging is associated with several morphological, cellular and molecular changes that deteriorate egg quality either by inducing abortive spontaneous egg activation (SEA) or by egg apoptosis. The reduced egg quality results in poor fertilization rate, embryo quality and reproductive outcome. Although postovulatory aging-induced abortive SEA has been reported in several mammalian species, the molecular mechanism(s) underlying this process remains to be elucidated. The postovulatory aging-induced morphological and cellular changes are characterized by partial cortical granules exocytosis, zona pellucida hardening, exit from metaphase-II (M-II)arrest and initiation of extrusion of second polar body in aged eggs. The molecular changes include reduction of adenosine 3',5'- cyclic monophosphate (cAMP) level, increase of reactive oxygen species (ROS) and thereby cytosolic free calcium (Ca(2+)) level. Increased levels of cAMP and/or ROS trigger accumulation of Thr-14/Tyr-15 phosphorylated cyclin-dependent kinase 1 (Cdk1) on one hand and degradation of cyclin B1 through ubiquitin-mediated proteolysis on the other hand to destabilize maturation promoting factor (MPF). The destabilized MPF triggers postovulatory aging-induced abortive SEA and limits various assisted reproductive technologies (ARTs) outcome in several mammalian species. Use of certain drugs that can either increase cAMP or reduce ROS level would prevent postovulatory aging-induced deterioration in egg quality so that more number of good quality eggs can be made available to improve ART outcome in mammals including human.
authors.affiliation: Cell Physiology Laboratory, Biochemistry Unit, Department of Zoology, Banaras Hindu University, Varanasi, 221005, UP, India. shilpaprasadskc@gmail.com.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Prasad
authors.affiliation: Cell Physiology Laboratory, Biochemistry Unit, Department of Zoology, Banaras Hindu University, Varanasi, 221005, UP, India. meenakshitiwariskc@gmail.com.
authors.forename: Meenakshi
authors.initials: M
authors.lastname: Tiwari
authors.affiliation: Genotoxicology and Cancer Biology Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221005, UP, India. kochbiplob@gmail.com.
authors.forename: Biplob
authors.initials: B
authors.lastname: Koch
authors.affiliation: Cell Physiology Laboratory, Biochemistry Unit, Department of Zoology, Banaras Hindu University, Varanasi, 221005, UP, India. shailchaubey@gmail.com.
authors.forename: Shail K
authors.initials: SK
authors.lastname: Chaube
mesh_terms: D000375:Aging; D000818:Animals; D006801:Humans; D008322:Mammals / Q000502:physiology*; D010060:Ovulation; D010063:Ovum / Q000502:physiology*; D012098:Reproduction