%0 Journal Article
%T Calcium ion currents mediating oocyte maturation events
%A Elisabetta Tosti
%J Reproductive Biology and Endocrinology
%D 2006
%I BioMed Central
%R 10.1186/1477-7827-4-26
%X Oogenesis is characterized by a unique process of cell division occurring only in gametes, called meiosis; whose goal is the production of haploid cells highly specialized for fertilization. In the majority of species the oocyte arrests in different stages of meiotic division, in particular, the block occurring in the first meiotic prophase (PI) marks the state of immature oocyte characterized by a prominent nucleus called the germinal vesicle (GV), which contains de-condensed transcriptionally active chromatin [[1] for a review]. As a general scheme, in response to a stimulus, meiosis is resumed and manifested by a germinal vesicle breakdown (GVBD), it then progresses to metaphase I (MI) or II (MII) where it undergoes a second arrest that is removed after successful fertilization.Oocyte maturation is usually defined as the period of progression from the first to the second meiotic arrest and involves coordinated nuclear and cytoplasmic modifications [2]. These are highly complex processes and their interplay is regulated by a series of sequential molecular events. Nuclear maturation starts with the GVBD, ends at the meiosis exit, and is marked by the presence of the two polar bodies. Cytoplasmic maturation is a more obscure process and involves both morphological and functional alterations related to: i) changes in the expression profile of cell cycle control proteins responsible for driving the oocyte towards developmental competencies [3-5]; ii) relocation of organelles [6-8]; iii) transcriptional modifications of mRNA [9], modification of the plasma membrane permeability [10,11]; iv) the differentiation of the calcium signalling machinery [12].Although the arrest at the PI stage seems to be strictly correlated with the oocyte growth, the meiotic stage correlated with fertilizable oocyte is species-specific. In some animals, oocytes are fertilized at the PI stage (anellida, plateyhelminthes, polychaeta, mollusca, arthropoda, echinoderms, and some mammals) or, on
%U http://www.rbej.com/content/4/1/26