About this Research Topic
The entire fertilization process is extremely delicate and precise. Normal fertilization involves the fusion of a capacitated and reacted sperm with an ovulated oocyte. During this process, several sperm go through the zona pellucida and attempt to fuse with the oocyte's plasma membrane (oolema); however, only one sperm will be accepted by the oocyte in most mammals.
Contrary to a passive role, the oocyte has a very active participation in fertilization and preimplantatory embryo. First, the oocyte prepares both nucleus and cytoplasm during their maturation. During nuclear maturation, genetic material is carefully split in the meiotic division; thus, any error in this division will be fatal for the embyo life. During cytoplasmic maturation, all organelles are prepared for supporting fertilization and preimplantatory embryo development. For instance, mature and correctly located cortical granules are essential to avoid polyspermy during cortical reaction. Similarly, healthy mitochondria are indispensable for ensuring the cellular energy required for the oocyte and the embryo metabolism.
When all processes, known and unknown, involved in the oocyte biology occur normally, we define the female gamete as a “competent oocyte”, even in those species of mammals that have polyspermic fertilization such as pigs. Although today we have a lot of evidence to describe a good quality oocyte, the oocyte is still the “black box” of fertilization. An in-depth understanding of the mechanisms that define a competent oocyte is necessary considering that the oocyte is an essential part in the assisted reproductive techniques. In addition, finding molecular markers for oocyte selection is the main goal for assisted reproduction in humans and animals.
This Research Topic aims to develop an integrative view of all mechanisms involved in oocyte maturation and oocyte fertilization such as meiotic maturation of oocytes (meiosis), cytoplasmic oocyte maturation (organelles and receptors maturation), in vivo and in vitro oocyte maturation, cumulus cells, monospermic and polyspermic fertilization, oocyte activation (physiological or parthenogenetic), calcium signaling, cell polarity establishment, and cortical reaction.
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