Zinc exocytosis is sensitive to myosin light chain kinase inhibition in mouse and human eggs

Hoi Chang Lee, Maxwell E. Edmonds, Francesca E. Duncan, Thomas V. O'Halloran, Teresa K. Woodruff*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Zinc dynamics are essential for oocyte meiotic maturation, egg activation, and preimplantation embryo development. During fertilisation and egg activation, the egg releases billions of zinc atoms (Zn2+) in an exocytotic event termed the 'zinc spark'. We hypothesised that this zinc transport and exocytosis is dependent upon the intracellular trafficking of cortical granules (CG) which requires myosin-actin-dependent motors. Treatment of mature mouse and human eggs with ML-7, a myosin light chain kinase inhibitor (MLCK), resulted in an 80% reduction in zinc spark intensity compared to untreated controls when activated with ionomycin. Moreover, CG migration towards the plasma membrane was significantly decreased in ML-7-treated eggs compared with controls when activated parthenogenetically with ionomycin. In sperm-induced fertilisation via intracytoplasmic sperm injection (ICSI), ML-7-treated mouse eggs exhibited decreased labile zinc intensity and cortical CG staining. Collectively, these data demonstrate that ML-7 treatment impairs zinc release from both murine and human eggs after activation, demonstrating that zinc exocytosis requires myosin light chain kinase activity. Further, these results provide additional support that zinc is likely stored and released from CGs. These data underscore the importance of intracellular zinc trafficking as a crucial component of egg maturation necessary for egg activation and early embryo development.

Original languageEnglish (US)
Pages (from-to)228-239
Number of pages12
JournalMolecular human reproduction
Issue number4
StatePublished - Apr 15 2020


  • cortical granule
  • egg
  • exocytosis
  • fertilisation
  • myosin light chain kinase
  • polyspermy
  • zinc spark
  • zona pellucida

ASJC Scopus subject areas

  • Genetics
  • Molecular Biology
  • Obstetrics and Gynecology
  • Cell Biology
  • Reproductive Medicine
  • Embryology
  • Developmental Biology


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