title: Role of gap junction-mediated communications in regulating large-scale chromatin configuration remodeling and embryonic developmental competence acquisition in fully grown bovine oocyte.
abstract: OBJECTIVE
  This study was aimed to test the hypothesis that gap junction mediated communications (GJC) are required to allow the progressive chromatin configuration remodeling (from GV1 to GV3) process to occur in fully grown oocytes in order to gain the final step of developmental competence acquisition, and that a premature disruption of GJC can alter this process.
  
  
  METHODS
  Bovine cumulus-oocytes complexes collected from medium antral follicles were cultured for 2, 4, 6 and 8 h in the presence of 10(-4) IU/ml of r-hFSH and with 2 mM of the non-selective PDE inhibitor 3-isobutyl-1-methyl-xanthine (IBMX) to prevent meiotic resumption. GJC functionality and chromatin configuration were monitored during the culture period. After meiotic arrest, the developmental capability of oocytes was assessed after IVM and IVF.
  
  
  RESULTS
  IBMX was effective in significantly sustaining GJC up to 6 h and maintaining meiotic arrest, when compared to control group. Moreover, the percentage of oocytes with less condensed chromatin (GV1) decreased within 4 h of culture, while the proportion of GV2 oocytes gradually increased up to 6 h. Interestingly, a decline in the proportion of GV2 oocytes and an increase in the proportion of GV3 oocytes were observed after 6 h of culture, when the major drop of GJC occurred. On the contrary, when GJC were uncoupled by adding 3 mM of 1-heptanol or through cumulus cells removal, chromatin condensation occurred rapidly throughout the culture period, more promptly in denuded oocytes. Moreover, the maintenance of GJC during meiotic arrest was accompanied by a significant increase of developmental competence compared to the control, as indicated by a higher percentage of hatched blastocysts and blastocyst cell number.
  
  
  CONCLUSIONS
  Altogether, our data indicate that both paracrine and junctional mechanisms are involved in modulating large-scale chromatin structure during the final phase of oocyte differentiation.
authors.affiliation: Reproductive and Developmental Biology Laboratory, Department of Health, Animal Science and Food Safety, University of Milan, 20133, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Lodde
authors.forename: Federica
authors.initials: F
authors.lastname: Franciosi
authors.forename: Irene
authors.initials: I
authors.lastname: Tessaro
authors.forename: Silvia C
authors.initials: SC
authors.lastname: Modina
authors.forename: Alberto M
authors.initials: AM
authors.lastname: Luciano
mesh_terms: D000818:Animals; D002417:Cattle; D002450:Cell Communication / Q000187:drug effects; D042002:Chromatin Assembly and Disassembly / Q000187:drug effects* / Q000235:genetics; D054885:Cumulus Cells / Q000166:cytology / Q000187:drug effects; D047108:Embryonic Development / Q000187:drug effects / Q000235:genetics; D005260:Female; D017629:Gap Junctions / Q000187:drug effects / Q000235:genetics; D059471:In Vitro Oocyte Maturation Techniques; D008540:Meiosis / Q000187:drug effects; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D009866:Oogenesis / Q000187:drug effects; D006080:Ovarian Follicle / Q000254:growth & development*; D010727:Phosphoric Diester Hydrolases / Q000008:administration & dosage*
chemical_list: D010727:Phosphoric Diester Hydrolases