Spindle function in Xenopus oocytes involves possible nanodomain calcium signaling

Intracellular calcium transients are a universal phenomenon at fertilization and are required for egg activation, but the exact role of Ca in second-polar-body emission remains unknown. On the other hand, similar calcium transients have not been demonstrated during oocyte maturation, and yet, manipu...

Full description

Saved in:
Bibliographic Details
Published in:Molecular biology of the cell 2016-11, Vol.27 (21), p.3273-3283
Main Authors: Li, Ruizhen, Leblanc, Julie, He, Kevin, Liu, X Johné
Format: Article
Language:English
Subjects:
Animals
Calcium - metabolism
Calcium Signaling - physiology
Calmodulin - metabolism
Cellular Microenvironment - physiology
Female
Fertilization - physiology
Meiosis - physiology
Microtubules - physiology
Oocytes - metabolism
Oocytes - physiology
Oogenesis - physiology
Polar Bodies
Spindle Apparatus - metabolism
Spindle Apparatus - physiology
Xenopus - metabolism
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Intracellular calcium transients are a universal phenomenon at fertilization and are required for egg activation, but the exact role of Ca in second-polar-body emission remains unknown. On the other hand, similar calcium transients have not been demonstrated during oocyte maturation, and yet, manipulating intracellular calcium levels interferes with first-polar-body emission in mice and frogs. To determine the precise role of calcium signaling in polar body formation, we used live-cell imaging coupled with temporally precise intracellular calcium buffering. We found that BAPTA-based calcium chelators cause immediate depolymerization of spindle microtubules in meiosis I and meiosis II. Surprisingly, EGTA at similar or higher intracellular concentrations had no effect on spindle function or polar body emission. Using two calcium probes containing permutated GFP and the calcium sensor calmodulin (Lck-GCaMP3 and GCaMP3), we demonstrated enrichment of the probes at the spindle but failed to detect calcium increase during oocyte maturation at the spindle or elsewhere. Finally, endogenous calmodulin was found to colocalize with spindle microtubules throughout all stages of meiosis. Our results-most important, the different sensitivities of the spindle to BAPTA and EGTA-suggest that meiotic spindle function in frog oocytes requires highly localized, or nanodomain, calcium signaling.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.E16-05-0338