Membrane and cortical abnormalities in post-ovulatory aged eggs: Analysis of fertilizability and establishment of the membrane block to polyspermy

Genevieve B. Wortzman, Janice Perry Evans

Research output: Contribution to journalArticle


Fertilization at increased times after ovulation is associated with poor reproductive outcomes. This study examines the effects of post-ovulatory ageing on egg membrane function through analyses of mouse eggs collected at 13 and 22h post-HCG ('young' and 'aged' eggs, respectively). Experiments in which fertilized zona pellucida-free young and aged eggs are challenged with additional sperm reveal that aged eggs are less able to establish a membrane block to prevent polyspermy, since sperm penetrate 24% of fertilized aged eggs but are unable to penetrate fertilized young eggs. This is not due to a failure of aged eggs to respond to fertilization, as the extent of sperm-induced cortical granule exocytosis is similar in aged and young eggs. Post-ovulatory ageing also affects egg membrane receptivity to sperm as a subset of zona pellucida-free aged eggs are slow to fertilize or resistant to fertilization. Sperm binding to young and aged eggs is similar, but aged eggs develop cytoskeletal abnormalities that may affect membrane/cortical function, such as the ability of the egg membrane to support sperm-egg fusion. These data demonstrate that the poor reproductive outcomes associated with post-ovulatory ageing could be a result of reduced fertilization, due to reduced egg membrane receptivity to sperm, or a result of increased incidence of polyspermy, due to the reduced ability to establish a membrane block to polyspermy. This analysis of egg membrane function deficiencies provides insights into post-ovulatory ageing and has implications for assisted reproductive technologies.

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalMolecular Human Reproduction
Issue number1
StatePublished - Jan 2005



  • Actin
  • Cytoskeleton
  • Egg activation
  • Polyspermy
  • Post-ovulatory ageing

ASJC Scopus subject areas

  • Obstetrics and Gynecology
  • Genetics
  • Developmental Biology
  • Embryology
  • Cell Biology

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