Chromatin organization during mouse oocyte growth

M. Zuccotti, A. Piccinelli, P. G. Rossi, S. Garagna, C. A. Redi

Research output: Contribution to journalArticlepeer-review


We investigated the changes in the organization of oocyte nuclear chromatin and nucleolar-associated chromatin throughout folliculogenesis. Zona-free oocytes were isolated from ovaries, grouped into seven classes according to size and chromatin organization, and analyzed after staining with Hoechst 33342. We show that oocyte differentiation from the dictyate stage to the conclusion of maturation is associated with either of two chromatin configurations. Initially, all oocytes are in the NSN configuration (nonsurrounded nucleolus oocytes; characterized by a Hoechst positive- chromatin pattern of small clumps forming a network on the nuclear surface, with a nucleolus nonsurrounded by chromatin). While growing, some of these NSN oocytes continue their development in the NSN configuration, whereas others shift (from class IV on) into the SN configuration (surrounded nucleolus oocytes; characterized by a threadlike chromatin organization that may partially surround the nucleolus or project towards the nuclear periphery). The percentage of SN oocytes increases both with increasing size of the oocyte (class I-III, 10-40 μm in diameter: 100% NSN vs. 0% SN; class VII 70-80 μm in diameter: 47.3% NSN vs. 52.3 SN, in 4-6-week-old females), and with aging (class VII: 94.1% NSN vs. 5.9% SN in 2-week-old females; 11.8% NSN vs. 8.2% SN in 56-week-old females). Further, we suggest as a working hypothesis that those oocytes that switch to the SN chromatin organization early in maturation may not be ovulated, even though this particular chromatin structure normally occurs just prior to ovulation.

Original languageEnglish
Pages (from-to)479-485
Number of pages7
JournalMolecular Reproduction and Development
Issue number4
Publication statusPublished - 1995


  • Chromatin structure
  • Folliculogenesis
  • Meiosis
  • Oogenesis

ASJC Scopus subject areas

  • Genetics
  • Developmental Biology
  • Cell Biology


Dive into the research topics of 'Chromatin organization during mouse oocyte growth'. Together they form a unique fingerprint.

Cite this