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Northwestern Scientists Discover Zinc Sparks Occur During Fertilization When Sperm Cell Meets Egg

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

Emily L. Que, Reiner Bleher, Francesca E. Duncan, Betty Y. Kong, Sophie C. Gleber, Stefan Vogt, Si Chen, Seth A. Garwin, Amanda R. Bayer, Vinayak P. Dravid, Teresa K. Woodruff, and Thomas V. O’Halloran,
Nature Chemistry (15 December 2014) 


Northwestern University article about discovery:
"Stunning Zinc Fireworks When Egg Meets Sperm", by Megan Fellman

Nature Chemistry

Images taken in the NUANCE-EPIC Facility with the Hitachi HD-2300A Dual EDS Cryo S/TEM

ABSTRACT:  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, 106 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.