Journal Article

Quantitative mapping of zinc fluxes in the mammalian egg reveals the origin of fertilization-induced zinc sparks

O'Halloran, Thomas V., Que, Emily L., Bayer, Amanda R., Garwin, Seth A., Gleber, Sophie C., Chen, Si, Bleher, Reiner, Vogt, Stefan, Dravid, Vinayak P., Duncan, Francesca E., Kong, Betty Y., Woodruff, Teresa K.

2015

Overview

Fertilization of a mammalian egg initiates a series of ‘zinc sparks’ that are necessary to induce the egg-to-embryo transition. Despite the importance of these zinc-efflux events little is known about their origin. To understand the molecular mechanism of the zinc spark we combined four physical approaches that resolve zinc distributions in single cells: a chemical probe for dynamic live-cell fluorescence imaging and a combination of scanning transmission electron microscopy with energy-dispersive spectroscopy, X-ray fluorescence microscopy and three-dimensional elemental tomography for high-resolution elemental mapping. We show that the zinc spark arises from a system of thousands of zinc-loaded vesicles, each of which contains, on average, 10 6 zinc atoms. These vesicles undergo dynamic movement during oocyte maturation and exocytosis at the time of fertilization. The discovery of these vesicles and the demonstration that zinc sparks originate from them provides a quantitative framework for understanding how zinc fluxes regulate cellular processes. The mammalian oocyte cell cycle is regulated by massive zinc fluxes which culminate in coordinated ejections of ~10 10 zinc ions at fertilization. Four single-cell physiochemical approaches (live-cell fluorescence imaging, scanning transmission electron microscopy with energy dispersive spectroscopy, X-ray fluorescence microscopy and tomography) reveal that these ‘zinc sparks’ originate from thousands of cortical vesicles which each release ~10 6 zinc ions.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 147/137 / 639/638/263/49 / 639/638/92 / 639/925/930/328 / Analytical Chemistry / Animals / Biochemistry / Cell Nucleus Division / CELLS / CHEMISTRY / Chemistry/Food Science / COPPER / DNA Probes - metabolism / Exocytosis / Female / Fertilization / Fluorescence microscopy / Fluorescent Dyes - chemical synthesis / Fluorescent Dyes - chemistry / Inorganic Chemistry / INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY / Mammals / Mice / Microscopy, Confocal / Microscopy, Electron, Scanning Transmission / OOCYTES / Oocytes - metabolism / Oocytes - ultrastructure / Organic Chemistry / Physical Chemistry / POTENTIALS / SPERM / TRAFFICKING / TRANSITION / TRANSPORTER / X-ray fluorescence / Zinc / Zinc - chemistry / Zinc - metabolism