|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Development, Vol 124, Issue 9 1845-1850, Copyright © 1997 by Company of Biologists
JOURNAL ARTICLES |
LK Berg and GM Wessel
Department of Molecular and Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.
Cortical granules are secretory vesicles poised at the cortex of an egg that, upon stimulation by sperm contact at fertilization, secrete their contents. These contents modify the extracellular environment and block additional sperm from reaching the egg. The role of cortical granules in blocking polyspermy is conserved throughout much of phylogeny. In the sea urchin, cortical granules accumulate throughout the cytoplasm during oogenesis, but in mature eggs the cortical granules are attached to the plasma membrane, having translocated to the cortex at some earlier time. To study the process of cortical granule translocation to the cell surface we have devised a procedure for maturation of sea urchin oocytes in vitro. Using this procedure, we examined the rate of oocyte maturation by observing the movement and breakdown of the germinal vesicle, the formation of polar bodies and the formation of the egg pronucleus. We find that oocyte maturation takes approximately 9 hours in the species used here (Lytechinus variegatus), from the earliest indication of maturation (germinal vesicle movement) to formation of a distinct pronucleus. We then observed the translocation of cortical granules in these cells by immunolocalization using a monoclonal antibody to hyalin, a protein packaged specifically in cortical granules. We found that the translocation of cortical granules in in vitro-matured oocytes begins with the movement of the germinal vesicle to the oocyte cell surface, and is 50% complete 1 hour after germinal vesicle breakdown. In the in vitro-matured egg, 99% of the cortical granules are at the cortex, indistinguishable from translocation in oocytes that mature in vivo. We have also found that eggs that mature in vitro are functionally identical to eggs that mature in vivo by four criteria. (1) The matured cells undergo a selective turnover of mRNA encoding cortical granule contents. (2) The newly formed pronucleus begins transcription of histone messages. (3) Cortical granules that translocate in vitro are capable of exocytosis upon activation by the calcium ionophore, A23187. (4) The mature egg is fertilizable and undergoes normal cleavage and development. In vitro oocyte maturation enables us to examine the mechanism of cortical granule translocation and other processes that had previously only been observed in static sections of fixed ovaries.
This article has been cited by other articles:
|
|
 |
|
  X.-Y. Liu, S.-F. Mal, D.-Q. Miao, D.-J. Liu, S. Bao, and J.-H. Tan Cortical granules behave differently in mouse oocytes matured under different conditions Hum. Reprod., December 1, 2005; 20(12): 3402 - 3413. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. W. Walker, L. M. Harrington, M. P. Lesser, and W. R. Fagerberg Nutritive Phagocyte Incubation Chambers Provide a Structural and Nutritive Microenvironment for Germ Cells of Strongylocentrotus droebachiensis, the Green Sea Urchin Biol. Bull., August 1, 2005; 209(1): 31 - 48. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. C. Millard, M. Terasaki, and L. M. Loew Second Harmonic Imaging of Exocytosis at Fertilization Biophys. J., June 1, 2005; 88(6): L46 - L48. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. R. Coorssen, P. S. Blank, F. Albertorio, L. Bezrukov, I. Kolosova, X. Chen, P. S. Backlund Jr, and J. Zimmerberg Regulated secretion: SNARE density, vesicle fusion and calcium dependence J. Cell Sci., May 15, 2003; 116(10): 2087 - 2097. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. M. Wessel, S. D. Conner, and L. Berg Cortical granule translocation is microfilament mediated and linked to meiotic maturation in the sea urchin oocyte Development, March 11, 2003; 129(18): 4315 - 4325. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. L. Abbott, R. A. Fissore, and T. Ducibella Identification of a Translocation Deficiency in Cortical Granule Secretion in Preovulatory Mouse Oocytes Biol Reprod, December 1, 2001; 65(6): 1640 - 1647. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V.S. Gross, G. Wessel, H.M. Florman, and T. Ducibella A Monoclonal Antibody That Recognizes Mammalian Cortical Granules and a32-Kilodalton Protein in Mouse Eggs Biol Reprod, August 1, 2000; 63(2): 575 - 581. [Abstract] [Full Text]
|
|
