Sperm actin and calmodulin during fertilization in the hamster: An immune electron microscopic study

Authors

  • Jean-Pierre Fouquet,

    Corresponding author
    1. Groupe d'Etude de la Formation et de la Maturation du Gamète Mâle, Laboratoire d'Histologie, UFR Biomédicale, 45 rue des Saints-Pères, Paris Cedex 06, France
    • Laboratoire d'Histologie, UFR Biomédicale, 45 rue des Saints-Pères, F 75270 Paris Cedex 06, France
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  • Dr. Benito Fraile,

    1. Groupe d'Etude de la Formation et de la Maturation du Gamète Mâle, Laboratoire d'Histologie, UFR Biomédicale, 45 rue des Saints-Pères, Paris Cedex 06, France
    Current affiliation:
    1. Départamento de Biologia Celular y Genética, Universidad de Alcala de Henares, Madrid, Espan̄a
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  • Marie-Louise Kann

    1. Groupe d'Etude de la Formation et de la Maturation du Gamète Mâle, Laboratoire d'Histologie, UFR Biomédicale, 45 rue des Saints-Pères, Paris Cedex 06, France
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Abstract

The distribution of actin and CaM in hamster spermatozoa was examined during the early events of fertilization using postembedding immunogold procedures. Actin was immunolocalized with a polyclonal antibody and two monoclonal antibodies. CaM was immunodetected with a polyclonal antibody. In epididymal sperm, actin labeling was found solely in the principal piece of the flagellum. CaM labeling was observed in the postacrosomal lamina, subacrosomal ring, and tip of the perforatorium. These distributions were not modified after capacitation and acrosome reaction. During the successive steps of sperm-egg fusion actin remained undetected in the sperm head whereas its location did not change in the flagellum. CaM distribution remained unmodified until the sperm head begins to decondense. At later stages of sperm head decondensation the postacrosomal lamina and its CaM labeling disappeared, whereas gold particles were still detected in the subacrosomal layer. The predominant location of actin into the egg cortex, particularly the microvillus-free area was confirmed. Except for the CaM labeling of the meiotic spindle, no special CaM location could be found throughout the egg. Thus, in hamster, a role for sperm actin in sperm-egg fusion appears unlikely. In contrast the CaM present in the Ca2+-rich postacrosomal lamina could be involved in the regulation of egg activation.

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