RESUMO
The stage-VI Xenopus oocyte has a very distinct animal-vegetal polarity with structural and functional asymmetry. In this study, we show the expression and distribution pattern of Na(+),K(+) -ATPase in stage-VI oocytes, and its changes following progesterone-induced maturation. Using enzyme-specific electron microscopy phosphatase histochemistry, [(3) H]-ouabain autoradiography, and immunofluorescence cytochemistry at light microscopic level, we find that Na(+),K(+) -ATPase activity is mainly confined to the animal hemisphere. Electron microscopy histochemical results also suggest that polarized distribution of Na(+),K(+) -ATPase activity persists following progesterone-induced maturation, and it becomes gradually more polarized towards the animal pole. The time course following progesterone-induced maturation suggests that there is an initial up-regulation and then gradual down-regulation of Na(+),K(+) -ATPase activity leading to germinal vesicle breakdown (GVBD). By GVBD, the Na(+),K(+) -ATPase activity is completely down-regulated due to endocytotic removal of pump molecules from the plasma membrane into the sub-cortical region of the oocyte. This study provides the first direct evidence for a marked asymmetric localization of Na(+),K(+) -ATPase activity in any vertebrate oocyte. Here, we propose that such asymmetry in Na(+),K(+) -ATPase activity in stage-VI oocytes, and their down-regulation following progesterone-induced maturation, is likely to have a role in the active state of the germinal vesicle in stage-VI oocytes and chromosomal condensation after GVBD.
Assuntos
Polaridade Celular , Oócitos/citologia , Oogênese/efeitos dos fármacos , Progesterona/farmacologia , ATPase Trocadora de Sódio-Potássio/metabolismo , Animais , Blastodisco/metabolismo , Blastodisco/ultraestrutura , Núcleo Celular/metabolismo , Núcleo Celular/ultraestrutura , Polaridade Celular/efeitos dos fármacos , Fase de Clivagem do Zigoto/citologia , Fase de Clivagem do Zigoto/efeitos dos fármacos , Fase de Clivagem do Zigoto/metabolismo , Fase de Clivagem do Zigoto/fisiologia , Regulação para Baixo/efeitos dos fármacos , Feminino , Microscopia Eletrônica de Transmissão , Modelos Biológicos , Oócitos/efeitos dos fármacos , Oócitos/metabolismo , Oócitos/ultraestrutura , Receptores de Progesterona/metabolismo , Distribuição Tecidual , Xenopus laevisAssuntos
Polaridade Celular/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/embriologia , Epitélio/embriologia , Proteínas Quinases JNK Ativadas por Mitógeno/fisiologia , Proteínas Supressoras de Tumor/genética , Animais , Animais Geneticamente Modificados , Blastodisco/embriologia , Blastodisco/metabolismo , Blastodisco/ultraestrutura , Padronização Corporal/genética , Padronização Corporal/fisiologia , Proteínas de Drosophila/fisiologia , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Embrião não Mamífero , Ativação Enzimática/fisiologia , Epitélio/ultraestrutura , Ligação Genética/fisiologia , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Modelos Biológicos , Mutação/fisiologia , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Proteínas Supressoras de Tumor/fisiologiaRESUMO
Based on their chromatin organization, antral oocytes can be classified into two classes, namely surrounded nucleolus (SN, chromatin forms a ring around the nucleolus), and not surrounded nucleolus (NSN, chromatin has a diffuse pattern). Oocytes of both classes are capable of meiotic resumption, but while SN oocytes, following fertilization, develop to term, NSN oocytes never develop beyond the two-cell stage. A recent study has shown that the position of the germinal vesicle (GV) can be used as a morphological marker predictive of oocyte meiotic competence, i.e. oocytes with a central GV have a higher meiotic competence than oocytes with an eccentric GV. In the present study, we have associated both markers with the aim of identifying, with more accuracy, the oocytes' developmental competence. Following their isolation, antral oocytes were classified on the basis of both SN and NSN chromatin configuration and their GV position, matured to metaphase II and fertilized in vitro. We demonstrated that the position of the GV is a good marker to predict the oocytes' developmental competence, but only when associated with the observation of the chromatin organization.
