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Resumption of Meiosis Induced by Meiosis-Activating Sterol Has a Different Signal Transduction Pathway than Spontaneous Resumption of Meiosis in Denuded Mouse Oocytes Cultured In Vitro1

Resumption of Meiosis Induced by Meiosis-Activating Sterol Has a Different Signal Transduction... AbstractThe sterol 4,4-dimethyl-5-cholesta-8,14,24-trien-3-ol (follicular fluid meiosis-activating sterol [FF-MAS]) isolated from human follicular fluid induces resumption of meiosis in mouse oocytes cultured in vitro. The purpose of this study was to examine the hypothesis that differential signal transduction mechanisms exist for FF-MAS-induced and spontaneous in vitro resumption of meiosis in mouse oocytes. Mouse oocytes were dissected from ovaries originating from mice primed with FSH 48 h before oocyte collection. Mechanically denuded germinal vesicle (GV) oocytes were in vitro matured in medium supplemented with hypoxanthine and FF-MAS or allowed to mature spontaneously; both groups were exposed to individual compounds known to inhibit specific targets in the cell. After 20–22 h of in vitro maturation, resumption of meiosis was assessed as the frequency of oocytes in GV breakdown (GVBD) stage. Pertussis toxin (2.5 μg/ml) did not influence resumption of meiosis in either group. Dibutyryl cyclic GMP (320 μM) inhibited FF-MAS-induced GVBD, but not spontaneous GVBD, whereas the subtype 5 phosphodiesterase-inhibitor zaprinast (50 μM) inhibited GVBD in both groups. Microinjection of the catalytic subunit of cAMP-dependent protein kinase into oocytes inhibited spontaneous GVBD, but not FF-MAS-induced GVBD. An inhibitor of cytoplasmic polyadenylation, cordycepin (80 μM), inhibited or retarded spontaneous GVBD to a further extent than it did FF-MAS-induced GVBD. Spontaneous GVBD was more sensitive to the histone H1 kinase-inhibitor olomoucine (250 μM) than was FF-MAS-induced GVBD. Addition of the mitogen-activated protein kinase (MAPK)-inhibitor PD 98059 (50 μM), phospholipase C-inhibitor U-73122 (10 μM), p21ras-inhibitor lovastatine (250 μM), and the src-like kinase inhibitor PP2 (20 μg/ml) inhibited FF-MAS-induced GVBD, but not spontaneous GVBD. Both MAPKs, extracellular regulated kinase (ERK) 1 and ERK2, were phosphorylated under FF-MAS-induced meiotic resumption, in contrast to spontaneous meiotic resumption, in which ERK1 and ERK2 phosphorylation occurred 2 h after GVBD. In the present study, we show that FF-MAS acts through an MAPK-dependent pathway, and we suggest that src-like kinase, p21ras, and phosphoinositide signaling lie upstream of MAPK in the FF-MAS-activated signaling pathway. Clearly, striking pathway differences are present between spontaneous versus FF-MAS-induced meiotic resumption. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biology of Reproduction Oxford University Press

Resumption of Meiosis Induced by Meiosis-Activating Sterol Has a Different Signal Transduction Pathway than Spontaneous Resumption of Meiosis in Denuded Mouse Oocytes Cultured In Vitro1

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References (69)

Publisher
Oxford University Press
Copyright
© 2001 by the Society for the Study of Reproduction, Inc.
ISSN
0006-3363
eISSN
1529-7268
DOI
10.1095/biolreprod65.6.1751
Publisher site
See Article on Publisher Site

Abstract

AbstractThe sterol 4,4-dimethyl-5-cholesta-8,14,24-trien-3-ol (follicular fluid meiosis-activating sterol [FF-MAS]) isolated from human follicular fluid induces resumption of meiosis in mouse oocytes cultured in vitro. The purpose of this study was to examine the hypothesis that differential signal transduction mechanisms exist for FF-MAS-induced and spontaneous in vitro resumption of meiosis in mouse oocytes. Mouse oocytes were dissected from ovaries originating from mice primed with FSH 48 h before oocyte collection. Mechanically denuded germinal vesicle (GV) oocytes were in vitro matured in medium supplemented with hypoxanthine and FF-MAS or allowed to mature spontaneously; both groups were exposed to individual compounds known to inhibit specific targets in the cell. After 20–22 h of in vitro maturation, resumption of meiosis was assessed as the frequency of oocytes in GV breakdown (GVBD) stage. Pertussis toxin (2.5 μg/ml) did not influence resumption of meiosis in either group. Dibutyryl cyclic GMP (320 μM) inhibited FF-MAS-induced GVBD, but not spontaneous GVBD, whereas the subtype 5 phosphodiesterase-inhibitor zaprinast (50 μM) inhibited GVBD in both groups. Microinjection of the catalytic subunit of cAMP-dependent protein kinase into oocytes inhibited spontaneous GVBD, but not FF-MAS-induced GVBD. An inhibitor of cytoplasmic polyadenylation, cordycepin (80 μM), inhibited or retarded spontaneous GVBD to a further extent than it did FF-MAS-induced GVBD. Spontaneous GVBD was more sensitive to the histone H1 kinase-inhibitor olomoucine (250 μM) than was FF-MAS-induced GVBD. Addition of the mitogen-activated protein kinase (MAPK)-inhibitor PD 98059 (50 μM), phospholipase C-inhibitor U-73122 (10 μM), p21ras-inhibitor lovastatine (250 μM), and the src-like kinase inhibitor PP2 (20 μg/ml) inhibited FF-MAS-induced GVBD, but not spontaneous GVBD. Both MAPKs, extracellular regulated kinase (ERK) 1 and ERK2, were phosphorylated under FF-MAS-induced meiotic resumption, in contrast to spontaneous meiotic resumption, in which ERK1 and ERK2 phosphorylation occurred 2 h after GVBD. In the present study, we show that FF-MAS acts through an MAPK-dependent pathway, and we suggest that src-like kinase, p21ras, and phosphoinositide signaling lie upstream of MAPK in the FF-MAS-activated signaling pathway. Clearly, striking pathway differences are present between spontaneous versus FF-MAS-induced meiotic resumption.

Journal

Biology of Reproduction – Oxford University Press

Published: Dec 1, 2001

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