Caratterizzazione dei meccanismi che regolano l'acquisizione della competenza allo sviluppo in vitro dell'ovocita nei mammiferi domestici : dottorato di ricerca in biotecnologie applicate alle scienze veterinarie e zootecniche : tesi di dottorato di ricerca

Characterization of the mechanisms involved in the acquisition of in vitro developmental competence in mammalian oocytes The female gamete acquires the capability to become an embryo after fertilization during folliculogenesis, when oocyte and somatic cells communicate by paracrine and junctional mechanisms, through a series of molecular events not yet well understood that modify both nuclear and cytoplasmic compartments. The purpose of this study was to clarify some of these events by studying the modifications of chromatin organization within the nucleus of immature bovine oocyte. Following fluorescence nuclear staining we found that the nuclear architecture undergoes dynamic changes during the final oocyte growth phase in which chromatin becomes progressively condensed. Furthermore we found that oocytes with a higher degree of chromatin condensation were characterized by a higher embryonic developmental capability after fertilization. Successively, ultrastructural studies of the nuclear and cytoplasmic compartments revealed that the process of chromatin reorganization could be related to profound key structural modifications, like nucleolar inactivation and remodeling of specific ooplasmic structures that take place during the later phases of oocyte growth. Furthermore, we investigate on the possible role of gap junction mediated communication between oocytes and surrounding cumulus cells in modulating changes of chromatin structure. As an increase of chromatin condensation corresponded to a higher incidence of communication interruption we concluded that this functional coupling could be implicated in large-scale chromatin remodeling process.