Localization of gamma-tubulin and cyclin B during early cleavage in physiologically polyspermic newt eggs

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Yasuhiro Iwao1, Tomomi Murakawa, Junko Yamaguchi

  • 1Department of Biological Science, Faculty of Science, Yamaguchi University, 753-8512 Yamaguchi, Japan. iwao@po.cc.yamaguchi-u.ac.jp

Development, Growth & Differentiation
|December 21, 2002
PubMed

Insights

This study reveals how gamma-tubulin and cyclin B1 distribution affects sperm nucleus entry in newt eggs. These findings support a model for nuclear degeneration in polyspermic eggs.

Area of Science:

  • Developmental Biology
  • Cell Biology
  • Reproductive Biology

Background:

  • Polyspermy, the fertilization of an egg by multiple sperm, is a critical factor influencing reproductive success.
  • Understanding the mechanisms that prevent or regulate polyspermy is essential for comprehending fertilization processes.
  • Newt eggs (Cynops pyrrhogaster) are physiologically polyspermic, making them a valuable model for studying polyspermy regulation.

Purpose of the Study:

  • To investigate the distribution and role of gamma-tubulin and cyclin B1 in the slow block to polyspermy in newt eggs.
  • To elucidate the mechanism of nuclear degeneration in accessory sperm nuclei within polyspermic newt eggs.
  • To validate a maturation-promoting factor (MPF) model for nuclear fate in polyspermic fertilization.

Main Methods:

  • Confocal laser microscopy was employed to visualize the localization of gamma-tubulin and cyclin B1.
  • Fertilized eggs of the newt Cynops pyrrhogaster were analyzed.
  • Quantitative and qualitative assessments of protein distribution within the egg and associated nuclei were performed.

Main Results:

  • Gamma-tubulin was more abundant in the animal hemisphere and accumulated significantly in the principal sperm nucleus and zygote nucleus, but not accessory sperm nuclei.
  • Cyclin B1 showed higher concentration in the animal hemisphere and zygote nucleus, with less in accessory sperm nuclei.
  • Cyclin B1 disappeared earlier from the zygote nucleus compared to accessory sperm nuclei, correlating with earlier metaphase entry and supporting the MPF model.

Conclusions:

  • The differential distribution of gamma-tubulin and cyclin B1 influences sperm aster formation and nuclear progression in newt eggs.
  • The findings support the MPF model, explaining the selective degeneration of accessory sperm nuclei in polyspermic fertilization.
  • These proteins play crucial roles in regulating nuclear events and preventing polyspermy in newt embryos.

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