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Modifications in chromatin morphology and organization during sheep oogenesis
Author(s) -
Russo Valentina,
Martelli Alessandra,
Berardinelli Paolo,
Di Giacinto Oriana,
Bernabò Nicola,
Fantasia Donatella,
Mattioli Mauro,
Barboni Barbara
Publication year - 2007
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/jemt.20462
Subject(s) - chromatin , biology , oocyte , telomere , microbiology and biotechnology , dna methylation , dna methyltransferase , methylation , genetics , andrology , embryo , dna , methyltransferase , gene expression , medicine , gene
This research has been designed to study the major events of nuclear remodeling that characterize sheep oocytes during the early stage of folliculogenesis (transition from preantral to antral stage). In particular, the modifications in large‐scale chromatin configuration, the global DNA methylation, and the process of telomere elongation have been investigated as crucial events of oocyte nuclear maturity. In addition, the spatio‐temporal distribution of the major enzymes involved in DNA methylation, the DNA methyltransferase 1 (Dnmt1), and in telomere elongation, telomerase catalytic subunit (TERT), have been described. To these aims, the nuclei of isolated oocytes were investigated using immunocytochemistry and Q‐FISH analyses. In absence of preliminary information, these nuclear determinants were compared with those of fully competent germ cells obtained from medium and preovulatory antral follicles. The nuclei of sheep oocytes acquired a condensed chromatin configuration, stable high levels of global DNA methylation, and a definitive telomere length already in the majority of late growing stage oocytes (110 μm) derived from early antral follicles. In addition, while the process of methylation resulted strictly related to oocyte diameter, the telomeric program appeared to be highly chromatin configuration‐dependent. The translocation of Dnmt1 and TERT from the nucleus to the cytoplasm in the oocytes derived from early antral follicles seems to confirm the definitive chromatin asset of these germ cells. In conclusion, changes in large‐scale chromatin structure, epigenesis, and telomere size in the sheep are established prior to oocyte acquires the ability to resume meiosis. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.