Several signaling pathways are involved in the control of cattle oocyte maturation

Abstract

The main limit of in vitro production of domestic mammal embryos comes from the low capacity of in vitro matured oocytes to develop after fertilization. As soon as they are separated from follicular environment, oocytes spontaneously resume meiosis without completion of their terminal differentiation. Roscovitine (ROS), an inhibitor of M-phase promoting factor (MPF) kinase activity reversibly blocks the meiotic resumption in vitro. However, in cattle maturing oocytes several cellular events such as protein synthesis and phosphorylation, chromatin condensation and nuclear envelope folding escape ROS inhibition suggesting the alternative pathways in oocyte maturation. We compared the level of synthesis and phosphorylation of several protein kinases during bovine cumulus oocyte complex (COC) maturation in vitro in the presence or not of epidermal growth factor (EGF) and ROS. We showed that during the EGF-stimulated maturation, ROS neither affected the decrease of EGF receptor (EGFR) nor did inhibit totally its phosphorylation in cumulus cells and also did not totally eliminate tyrosine phosphorylation in oocytes. However, ROS did inhibit the Phosphoinositide 3-kinase (PI3) activity when oocytes mature without EGF. Accumulation of Akt/PKB (protein kinase B), JNK1/2 (jun N-terminal kinases) and Aurora-A in oocytes during maturation was not affected by ROS. However, the phosphorylation of Akt but not JNKs was diminished in ROS-treated oocytes. Thus, PI3 kinase/Akt, JNK1/2 and Aurora-A are likely to be involved in the regulation of bovine oocyte maturation and some of these pathways seem to be independent to MPF activity and meiotic resumption. This complex regulation may explain the partial meiotic arrest of ROS-treated oocytes and the accelerated maturation observed after such treatment.

Activation of Akt (protein kinase B) stimulates metaphase I to metaphase II transition in bovine oocytes

“…It should be mentioned here that this result is not in agreement with observations made by Vigneron et al (2004b). These authors reported no or only very low abundance of Akt in the GV stage (time 0) of bovine oocytes.…”

“…It was previously shown that another kinase named Akt (protein kinase B; PKB) is also abundant in mouse and bovine oocytes (Hoshino et al 2004, Vigneron et al 2004a, 2004b. The results reported indicate that Akt is likely to participate in the maturation of oocytes, probably independent of MPF activation.…”

Glycogen synthase kinase 3B in bovine oocytes and granulosa cells: possible involvement in meiosis during in vitro maturation

“…MAPK1 and MAPK3 (also known as ERK2 and ERK1 respectively) and maturation promoting factor (MPF), a complex of cyclin B1 and cell-cycle controller p34 kinase cyclindependent kinase 1 (CDK1) constituted the main signalling pathways of oocyte maturation control (see review (Liang et al 2007)). We showed previously that several protein kinases are differentially activated in bovine oocytes during IVM: MAPK3/MAPK1, jun N-terminal kinase (JNK), AKT, Aurora kinases (Vigneron et al 2004a, 2004b, Uzbekova et al 2008 and AMPactivated protein kinase (AMPK; Tosca et al 2007). Another member of MAPK super-family, MAPK14 (alias p38) was expressed in porcine cumulus-oocyte complexes (COCs) and its activation varied during IVM (Villa-Diaz & Miyano 2004).…”

Identification and analysis of the jnk1 gene in polyploid hybrids of red crucian carp (Carassius auratus red var.) and common carp (Cyprinus carpio L.)

“…JNK signaling is also involved in controlling oocyte development in other vertebrates (Vigneron et al, 2004;Browaeys-Poly et al, 2005). Our previous studies indicated that the expression of the jnk1 gene displays distinct patterns during the sex reversal of the rice-field eel M. albus, which has some typical features of natural sexual reversal during its lifecycle (Xiao, 1995;Xiao and Liu, 1995;Xiao et al, 2007).…”