Anchoring cortical granules in the cortex ensures trafficking to the plasma membrane for post-fertilization exocytosis

Nat Commun. 2019 May 22;10(1):2271. doi: 10.1038/s41467-019-10171-7.

Abstract

Following fertilization, cortical granules exocytose ovastacin, a metalloendopeptidase that cleaves ZP2 in the zona pellucida surrounding mouse eggs to prevent additional sperm binding. Using high- and super-resolution imaging with ovastacinmCherry as a fluorescent marker, we characterize cortical granule dynamics at single granule resolution in transgenic mouse eggs. Newly-developed imaging protocols provide an unprecedented view of vesicular dynamics near the plasma membrane in mouse eggs. We discover that cortical granule anchoring in the cortex is dependent on maternal MATER and document that myosin IIA is required for biphasic trafficking to the plasma membrane. We observe local clearance of cortical actin during exocytosis and determine that pharmacologic or genetic disruption of trafficking to the plasma membrane impairs secretion of cortical granules and results in polyspermy. Thus, the regulation of cortical granule dynamics at the cortex-plasma membrane interface is critical for exocytosis and the post-fertilization block to sperm binding that ensures monospermic fertilization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens / metabolism
  • Cell Membrane / metabolism
  • Cytoplasmic Granules / metabolism*
  • Egg Proteins / metabolism
  • Exocytosis / physiology*
  • Female
  • Intravital Microscopy
  • Luminescent Proteins / chemistry
  • Luminescent Proteins / genetics
  • Male
  • Metalloproteases / chemistry
  • Metalloproteases / genetics
  • Metalloproteases / metabolism
  • Mice
  • Mice, Transgenic
  • Microscopy, Fluorescence
  • Red Fluorescent Protein
  • Sperm-Ovum Interactions / physiology*
  • Zona Pellucida / metabolism*
  • Zona Pellucida Glycoproteins / metabolism

Substances

  • Antigens
  • Egg Proteins
  • Luminescent Proteins
  • Nalp5 protein, mouse
  • Zona Pellucida Glycoproteins
  • Zp2 protein, mouse
  • Astl protein, mouse
  • Metalloproteases