Role of calcium during release of mollusc oocytes from their blocks in meiotic prophase and metaphase

Abstract

Bivalve oocytes constitute an excellent model to study the mechanisms which control cell division, since they arrest at different stages of tile meiotic process and respond quite synchronously to various external signals regulating their evolution. Different situations were observed, according to the species, which required a more careful analysis. For example, the same serotonin (5-HT) signal was found to drive prophase-arrested oocytes of Spisula to the female pronucleus stage, whereas Ruditapes oocytes stopped in metaphase 1. In this last species, 5-HT treatment thus represents a necessary prerequisite for further development since sperm cannot penetrate prophase-arrested oocytes, in contrast to the situation found in Spisula. The reasons for these differences cannot be found at the level of the receptors and second messengers. In both species, we found that Ca -'+ was involved as a second messenger and required to release oocytes from their blocks in prophase and metaphase 1. This is an unexpected and puzzling situation since MPF is activated by the prophase Ca-" surge and inactivated during metaphase-anaphase transition. The mechanisms underlying these paradoxical situations are discussed, taking into account results from previous observations and experiments. Briefly, our data suggest: i) that the absence of K + sensitive voltage-gated Ca -'+ channels may be responsible for the unfertilizability of prophasearrested Ruditapes oocytes; and ii) that functional variations in the network of activated kinases present in prophase and metaphase oocytes may be responsible for the divergent responses exhibited by Spisula and Ruditapes oocytes. In particular, these oocytes differ in their sensitivity to Ca 2'/calmodulin antagonists and in tyrosine phosphorylation of their activated p34 cJ~-' kinase. calcium stores / oocyte maturation / serotonin / pelecypod molluscs

Cellular effects of olomoucine, an inhibitor of cyclin‐dependent kinases

“…sampling was carried out after 0, 2,4.6, 8,9, 10, 11, 12, 14, 16 h for A carterue and 0. 1,2,3,4,5,6,7,8,10,12 h for T weissflogii.…”

Identification of a new class of protein kinases represented by eukaryotic elongation factor-2 kinase

“…17 and 18). eEF-2 kinase activity is found in virtually all mammalian tissues as well as in various invertebrate organisms (19). eEF-2 kinase phosphorylates eEF-2 at two threonine residues that are conserved in all eukaryotes and are located within a GTP-binding domain (17,18).…”

A microarray-based analysis of oocyte quality in the European clam Ruditapes decussatus

“…The molecular cascade, and the underlying genes involved in this phenomenon, has been little studied in bivalves showing mainly the crucial role of Ca 2+ signaling pathway during oocyte maturation (e.g. ; Abdelmajid et al 1993;Colas and Dubé 1998;Deguchi and Morisawa 2003;Leclerc et al 2000;Stricker and Smythe 2001;Zhang et al 2009). It has been suggested that continuously synthesized, short-lived proteins are responsible for maintaining metaphase arrest in some molluscan oocytes, with cyclin regulatory proteins as good candidates since their disappearance triggered A C C E P T E D M A N U S C R I P T metaphase/anaphase transition and polar body extrusion (Colas and Dubé 1998).…”

“…Ruditapes and other molluscs, calcium may act via a calcium calmodulin-kinase since calcium calmodulin antagonists were able to prevent metaphase I release and cyclin degradation upon fertilization (Abdelmajid et al 1993;Colas and Dubé 1998;Leclerc et al 2000;Whitaker 1996;Zhang et al 2009). In this work we found the enzyme Calcium/calmodulin-dependent 3',5"-cyclic nucleotide phosphodiesterase 1C (Cam-PDE1C) (FC=1.7) among the genes more abundant in good quality oocytes.…”