Fertilization in Voltage-Clamped Sea Urchin Eggs

  • Edward L. Chambers


Following insemination of the voltage-clamped sea urchin egg a characteristic component of the activation current is the initial shoulder with abrupt onset. This is the counterpart of the shoulder of the activation potential, and has a duration of ~12s, equal to that of the latent period. After attaining a maximum, the shoulder of the activation current is followed by a large increase in the inward current culminating in the major peak at ~3Is. One of the most interesting findings in voltage clamp studies of fertilization is that the shoulder phase can be fully, or partially, dissociated from the subsequent phases of the activation current by holding the egg’s membrane potential (Vm) in the neighborhood of the resting value (−70 mV). When the dissociation occurs, either complete or partial, the attached sperm fails to enter the egg. When the dissociation is complete, the isolated shoulder (duration ~11s, now termed a sperm transient current) terminates abruptly, subsequent phases of the activation current do not occur, and the egg otherwise remains in the unfertilized state. When the dissociation is partial, the same isolated shoulder (a step-like current profile, abrupt turn-on and turn-off, duration of ~ I2s) is observed, but from 5 to 25s after return of the current to the holding level, the delayed second or major current phase of a modified activation current occurs, accompanied by delayed elevation of the fertilization envelope. Cleavage fails to occur. Dissociation of the shoulder component from the subsequent phases of the activation current together with suppression of sperm entry is also observed in oocytes (germinal vesicle stage) when single sperm attach. Oocytes have a Vm of –70 mV, and, because of the 15– to 20–fold higher membrane conductance compared to that of eggs, single sperm can depolarize the oocytes’ Vm by only 7 to 8 mV.

These data are consistent with the conclusion that unless depolarization to the neighborhood of 0 mV occurs, the shoulder component is dissociated from subsequent phases of the activation current and sperm entry will not occur. One possibility is that dissociation of the shoulder component accompanied by failure of sperm entry results from a suppressive effect of negative Vm on fusion of the sperm and egg plasma membranes. However, capacitance measurements carried out on eggs using a patch clamp method indicate that coincidentally with the abrupt turn-on of the shoulder current, cytoplasmic continuity between sperm and egg is attained. Nonetheless, the incipient stages of sperm incorporation were shortly terminated since simultaneously with the cutoff of current (which ends the dissociated shoulder component), the fusion event was reversed. Patch clamp measurements have established that the conductance increase which generates the inward shoulder current is not global, but localized to the immediate site of sperm attachment. A consequence of the restriction of the conductance increase to a localized site is that the density (current per unit surface area) could be large. This could result in alteration of the concentration of ions at the site of the entering sperm, and suppress its penetration. This possibility is currently under investigation in ion substitution experiments.


Activation Current Transient Current Germinal Vesicle Stage Fertilization Envelope Patch Clamp Measurement 
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  1. Allen, R. and J. L. Griffin. 1958. The time sequence of early events in the fertilization of sea urchin eggs. I. The latent period and the cortical reaction. Exp. Cell Res. 15: 163–173.PubMedCrossRefGoogle Scholar
  2. Chambers, E. L. and J. de Armendi. 1979. Membrane potential, action potential and activation potential of eggs of the sea urchin, Lytechinus variegatus. Exp. Cell Res. 122: 203–218.CrossRefGoogle Scholar
  3. David, C., J. Halliwell, and M. Whitaker. 1988. Some properties of the membrane currentsGoogle Scholar
  4. underlying the fertilization potential in sea urchin eggs. J. Physiol. (Load.) 402:139–154.Google Scholar
  5. Gould, M. and J. L. Stephano. 1987. Electrical responses of eggs to acrosomal proteins similar to those induced by sperm. Science 235: 1654–1656.PubMedCrossRefGoogle Scholar
  6. Gould-Somero, M. 1981. Localized gating of egg Na’ channels. Nature 291: 254–256.CrossRefGoogle Scholar
  7. Gould-Somero, M. and L. A. Jaffe. 1984. Control of cell fusion at fertilization by membrane potential. p. 27–38. In: Cell Fusion: Gene Transfer and Transformation. R. F. Beers and E. G. Bassett (Eds.) Raven Press, New York.Google Scholar
  8. Gundersen, G. G., L. Medill, and B. M. Shapiro. 1986. Sperm surface proteins are incorporated into the egg membrane and cytoplasm after fertilization. Dev. Biol. 113: 207–217.CrossRefGoogle Scholar
  9. Hagiwara, S. and L. A. Jaffe. 1979. Electrical properties of egg membranes. Annu. Rev. Biophys. Bioeng. 8: 385–417.PubMedCrossRefGoogle Scholar
  10. Jaffe, L. A. 1976. Fast block to polyspermy in sea urchin eggs is electrically mediated. Nature (Loud.) 261: 68–71.CrossRefGoogle Scholar
  11. Jaffe, L. A., M. Gould-Somero, and L. Holland. 1979. Ionic mechanism of the fertilization potential of the marine worm, Urechis caupo (Echiura). J. Gen. Physiol. 73: 469–492.PubMedCrossRefGoogle Scholar
  12. Jaffe, L. A., R. T. Kado, and L. Muncy. 1985. Propagating potassium and chloride conductances during activation and fertilization of the egg of the frog, Rana pipiens. J. Physiol. (Land.) 368: 227–242.Google Scholar
  13. Jaffe, L. A. and K. R. Robinson. 1978. Membrane potential of the unfertilized sea urchin egg. Dev. Biol. 62: 215–228.PubMedCrossRefGoogle Scholar
  14. Kline, D. 1986. A direct comparison of the extracellular current observed in the activating frog egg with the vibrating probe and patch clamp techniques. p. 1–8. In: Ionic Currents in Development. R. Nuccitelli (Ed.). Alan R. Liss, New York.Google Scholar
  15. Kline, D. and R. Nuccitelli. 1985. The wave of activation current in the Xenopus egg. Dev. Biol. 111: 471–487.PubMedCrossRefGoogle Scholar
  16. Longo, F. J. 1986. Surface changes at fertilization: Integration of sea urchin (Arbacia punctulata) sperm and oocyte plasma membranes. Dev. Biol. 116: 143–159.PubMedCrossRefGoogle Scholar
  17. Longo, F. J., J. W. Lynn, D. H. McCulloh, and E. L. Chambers. 1986. Correlative ultrastructural and electrophysiological studies of sperm-egg interactions of the sea urchin, Lytechinus variegatus. Dec. Biol. 118: 155–166.CrossRefGoogle Scholar
  18. Lynn, J. W. and E. L. Chambers. 1984. Voltage clamp studies of fertilization in sea urchin eggs. I. Effect of clamped membrane potential on sperm entry, activation, and development. Dev. Biol. 102: 98–109.PubMedCrossRefGoogle Scholar
  19. Lynn J. W. and E. L. Chambers. 1987. Effects of cytochalasin B on egg activation currents in Lytechinus variegatus eggs voltage clamped at -20 mV. J. Cell Biol. 105: 359a.Google Scholar
  20. Lynn, J. W., D. H. McCulloh, and E. L. Chambers. 1988. Voltage clamp studies of fertilization in sea urchin eggs. II. Current patterns in relation to sperm entry, non-entry, and activation. Dev. Biol. 128: 305–323.PubMedCrossRefGoogle Scholar
  21. McCulloh, D. H. and E. L. Chambers. 1985. Localization and proagation of membrane conductance changes during fertilization in eggs of the sea urchin, Lytechinus variegatus. J. Cell Biol. 101: 230a.Google Scholar
  22. McCulloh, D. H. and E. L. Chambers. 1986a. When does the sperm fuse with the egg? J. Gen. Physiol. 88: 38a - 39a.Google Scholar
  23. McCulloh, D. H. and E. L. Chambers. 1986b. Fusion and “unfusion” of sperm and egg are voltage dependent in the sea urchin Lytechinus variegatus. J. Cell Biol. 103: 236a.Google Scholar
  24. McCulloh, D. H., P. Ivonnet, and E. L. Chambers. 1988. Actin polymerization precedes fertilization cone formation and sperm entry in the sea urchin egg. Cell Motil. Cytoskeleton 10: 345.Google Scholar
  25. McCulloh, D. H., J. W. Lynn, and E. L. Chambers. 1987. Membrane depolarization facilitates sperm entry, large fertilization cone formation, and prolonged current responses in sea urchin oocytes. Dev. Biol. 124: 177–190.PubMedCrossRefGoogle Scholar
  26. Schackman, R. W., R. Christen, and B. M. Shapiro. 1984. Measurement of plasma membrane and mitochondrial potentials in sea urchin sperm. J. Biol. Chem. 259: 13914–13922.Google Scholar

Copyright information

© Springer Science+Business Media New York 1989

Authors and Affiliations

  • Edward L. Chambers
    • 1
  1. 1.Department of Physiology and BiophysicsUniversity of Miami School of MedicineMiamiUSA

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