Signalling events during Xenopus laevis vitellogenesis

SERRANO, M.A.; LUQUE, M. E.; SÁNCHEZ S. S.

Congreso; VI International Meeting of the Latin American of Developmental Biology; 2012

LSBD

The development of oogonia into oocytes is described as oogenesis. In many oviparous vertebrates the growth of oocytes is the result of a cell regulation process, called vitellogenesis. This process is characterized by hepatic production of the glycoprotein vitellogenin (VTG) that is transported via the bloodstream to the ovary where it is incorporated by oocytes. In the amphibian ovary the three different stages previtellogenesis, vitellogenesis and maturation are regulated by three kinds of signals: endocrine (gonadotropins, estrogens), paracrine (TGF-β, BMPs and Activins) and juxtacrine mediated by gap junctions (Ca++,cAMP/IP3). To analyse the participation of paracrine signalling, we determined the gene expression of Xepac and BMP signalling pathway components. The results showed the presence of Xepac, BMP2, 4, 7 and their receptors during X. laevis oogenesis. To determine the role of IP3 and Xepac during vitellogenesis we performed assays with different inhibitors. Oocytes were treated with U-73122 (PLC specific inhibitor), verapamil, nifedipine, diltiazem and amiloride (to block voltage-operated channels), theophylline (phosphodiesterase inhibitor), neomycin (PIP2 hydrolysis inhibitor) and H89 (Protein kinase A inhibitor). Rescue experiments were performed with cdbAMP (Dibutyryl cyclic-AMP) and with A23187 (calcium ionophore). The results showed that IP3 signalling pathway is implicated in VTG uptake. Because of this, we suggest that oogenesis is a complex process coordinated by a cross-talk between the molecules of different signalling pathways.