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Molecular reproduction and development2001; 60(2); 260-269; doi: 10.1002/mrd.1086

Organisation of the cytoskeleton during in vitro maturation of horse oocytes.

Abstract: Meiotic maturation of mammalian oocytes is a complex process during which microfilaments and microtubules provide the framework for chromosomal reorganisation and cell division. The aim of this study was to use fluorescence and confocal laser scanning microscopy to examine changes in the distribution of these important cytoskeletal elements and their relationship to chromatin configuration during the maturation of horse oocytes in vitro. Oocytes were cultured in M199 supplemented with pFSH and eLH and, at 0, 12, 24, and 36 hr after the onset of culture, they were fixed for immunocytochemistry and stained with markers for microtubules (a monoclonal anti-alpha-tubulin antibody), microfilaments (AlexaFluor 488 Phalloidin) and DNA (TO-PRO(3)). At the germinal vesicle stage, oocyte chromatin was amorphous and poorly condensed and the microfilaments and microtubules were distributed relatively evenly throughout the ooplasm. After germinal vesicle breakdown, the microtubules were aggregated around the now condensed chromosomes and the microfilaments had become concentrated within the oocyte cortex. During metaphase I, microtubules were detected only in the meiotic spindle, as elongated asters encompassing the aligned chromosomes, and, as maturation progressed through anaphase-I and telophase-I, the spindle assumed a more eccentric position and gradually rotated to assist in the separation of the homologous chromosomes and in the subsequent formation of the first polar body. During metaphase II, the meiotic spindle was a symmetrical, barrel-shaped structure with two poles and with the chromosomes aligned along its midline. At this stage, microtubules were found intermingled with chromatin within the polar body and, although, the bulk of the microfilaments remained within the oocyte cortex, a rich domain was found overlying the spindle. Thus, during the in vitro maturation of horse oocytes both the microfilament and microtubular elements of the cytoskeleton were seen to reorganise dramatically in a fashion that appeared to enable chromosomal alignment and segregation.
Publication Date: 2001-09-13 PubMed ID: 11553927DOI: 10.1002/mrd.1086Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research sought to understand how the cytoskeleton—a network of protein filaments in a cell—changes during the maturation of horse oocytes—sex cells or eggs—in a laboratory setting. The findings show that the microtubules and microfilaments, important elements of the cytoskeleton, undergo dramatic rearrangements to facilitate the alignment and separation of chromosomes.

Methodology

  • The research team used fluorescence and confocal laser scanning microscopy, techniques that allow for cell structure visualization, to observe changes in microfilaments and microtubules—the protein filaments that form the cell’s cytoskeleton—and their relationship to chromosomal reconfiguration.
  • Horse oocytes were cultured in a medium enriched with pFSH and eLH hormones that stimulate follicle growth and egg development.
  • At 0, 12, 24, and 36 hours after the initiation of the culture, the oocytes were fixed and stained for immunocytochemistry with markers specific for microtubules, microfilaments, and DNA to visualize these cellular structures.

Results

  • At the beginning of the maturation process, the chromatin—the material of which chromosomes are made—was unorganized and loosely packed, and the microfilaments and microtubules were evenly distributed across the oocyte.
  • With progressing maturation, the microtubules congregated around the now organized chromosomes, whereas the microfilaments concentrated within the cell’s cortex—the outer part of the cytoplasm.
  • Different changes were observed during the different stages of meiosis, the process that divides the genetic material. During metaphase I and metaphase II, striking microtubule reorganizations were detected around the aligned chromosomes, with the spindles assuming different positions and forms to facilitate chromosome separation and alignment.
  • In the final stages of maturation, although the majority of the microfilaments stayed within the cortex, one area rich in these elements was located above the spindle.

Conclusion

  • The in vitro maturation process of horse oocytes involves significant reorganization of the cytoskeletal elements, with the microfilaments and microtubules adapting their positions to facilitate the alignment and separation of the chromosomes.
  • This research provides a detailed view of the cytoskeletal dynamics during horse oocyte maturation and hints towards the critical role of cytoskeletal elements in successful cell division and reproduction.

Cite This Article

APA
Tremoleda JL, Schoevers EJ, Stout TA, Colenbrander B, Bevers MM. (2001). Organisation of the cytoskeleton during in vitro maturation of horse oocytes. Mol Reprod Dev, 60(2), 260-269. https://doi.org/10.1002/mrd.1086

Publication

ISSN: 1040-452X
NlmUniqueID: 8903333
Country: United States
Language: English
Volume: 60
Issue: 2
Pages: 260-269

Researcher Affiliations

Tremoleda, J L
  • Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands. J.Tremoleda@vet.uu.nl
Schoevers, E J
    Stout, T A
      Colenbrander, B
        Bevers, M M

          MeSH Terms

          • Actin Cytoskeleton / chemistry
          • Actin Cytoskeleton / ultrastructure
          • Animals
          • Chromatin / chemistry
          • Chromatin / ultrastructure
          • Cytoskeleton / chemistry
          • Cytoskeleton / ultrastructure
          • Female
          • Horses / physiology
          • Microscopy, Fluorescence
          • Microtubules / chemistry
          • Microtubules / ultrastructure
          • Oocytes / chemistry
          • Oocytes / growth & development
          • Oocytes / ultrastructure
          • Spindle Apparatus / chemistry
          • Spindle Apparatus / ultrastructure

          Citations

          This article has been cited 9 times.
          1. Totsuka T, Ohsugi M, Akera T. Ca(2+)-driven cytoplasmic backflow ensures spindle anchoring in fertilized mouse eggs. Curr Biol 2025 Aug 18;35(16):3839-3850.e5.
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