title: In vitro grown sheep preantral follicles yield oocytes with normal nuclear-epigenetic maturation.
abstract: BACKGROUND
  Assisted reproductive technologies allow to utilize a limited number of fully grown oocytes despite the presence in the ovary of a large pool of meiotically incompetent gametes potentially able to produce live births. In vitro folliculogenesis could be useful to recruit these oocytes by promoting their growth and differentiation.
  
  
  RESULTS
  In vitro folliculogenesis was performed starting from sheep preantral (PA) follicles to evaluate oocyte nuclear/epigenetic maturation. Chromatin configuration, quantification of global DNA methylation, and epigenetic remodelling enzymes were evaluated with immunocytochemistry, telomere elongation was assessed with the Q-FISH technique, while the DNA methylation status at the DMRs of maternally IGF2R and BEGAIN, and paternally H19 methylated imprinted genes was determined by bisulfite sequencing and COBRA. Specifically, 70% of PA underwent early antrum (EA) differentiation and supported in culture oocyte global DNA methylation, telomere elongation, TERT and Dnmt3a redistribution thus mimicking the physiological events that involve the oocyte during the transition from secondary to tertiary follicle. Dnmt1 anticipated cytoplasmic translocation in in vitro grown oocytes did not impair global and single gene DNA methylation. Indeed, the in vitro grown oocytes acquired a methylation profile of IGF2R and BEGAIN compatible with the follicle/oocyte stage reached, and maintained an unmethylated status of H19. In addition, the percentage of oocytes displaying a condensed chromatin configuration resulted lower in in vitro grown oocytes, however, their ability to undergo meiosis and early embryo development after IVF and parthenogenetic activation was similar to that recorded in EA follicle in vivo grown oocytes.
  
  
  CONCLUSIONS
  In conclusion, the in vitro folliculogenesis was able to support the intracellular/nuclear mechanisms leading the oocytes to acquire a meiotic and developmental competence. Thus, the in vitro culture may increase the availability of fertilizable oocytes in sheep, and become an in vitro translational model to investigate the mechanisms governing nuclear/epigenetic oocyte maturation.
authors: Department of Comparative Biomedical Science, University of Teramo, Teramo, Italy.
authors: Barbara
authors: B
authors: Barboni
authors: Valentina
authors: V
authors: Russo
authors: Sandra
authors: S
authors: Cecconi
authors: Valentina
authors: V
authors: Curini
authors: Alessia
authors: A
authors: Colosimo
authors: Maria Luigia A
authors: ML
authors: Garofalo
authors: Giulia
authors: G
authors: Capacchietti
authors: Oriana
authors: O
authors: Di Giacinto
authors: Mauro
authors: M
authors: Mattioli
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism; D042002:Chromatin Assembly and Disassembly / Q000235:genetics; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D044127:Epigenesis, Genetic; D005260:Female; D005307:Fertilization in Vitro; D005453:Fluorescence; D018507:Gene Expression Regulation, Developmental; D017404:In Situ Hybridization, Fluorescence; D042541:Intracellular Space / Q000201:enzymology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000201:enzymology; D006080:Ovarian Follicle / Q000166:cytology* / Q000254:growth & development*; D010312:Parthenogenesis / Q000235:genetics; D021381:Protein Transport; D000074407:SAP90-PSD95 Associated Proteins; D012756:Sheep; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000378:metabolism
chemical_list: D002843:Chromatin; D009419:Nerve Tissue Proteins; D000074407:SAP90-PSD95 Associated Proteins; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D019098:Telomerase