Immunochemical Characterization of a Human Sperm Fibrous Sheath Protein, Its Developmental Expression Pattern, and Morphogenetic Relationships with ActinDenise Escaliera, Jean-Marc Galloc, and Joseph Schrévelba Laboratoire de Biologie de la Reproduction et du Développement, CHU Bicêtre, Le Kremlin Bicêtre, France b Museum National d'Histoire Naturelle, ERS CNRS 156, Paris, France c Department of Neurology, Institute of Psychiatry, London, United Kingdom Correspondence to: Denise Escalier, INSERM U25, Hôpital Necker, 149-161, rue de Sèvres, 75743 Paris Cedex 15, France. Among the monoclonal antibodies (MAbs) prepared against human sperm extracts, MAb 4F7 was found to be specific to the human and Macaca fascicularis sperm cytoskeletal fibrous sheath (FS). In Western blotting, MAb 4F7 stains a doublet of polypeptides of about Mr 95 x 103 in extracts of human sperm cells. These polypeptides are not recognized by the KL1 anti-cytokeratin MAb, nor by the MAbs known to bind to the carboxy terminal (IFA) and to the amino terminal (ME101) rod domain of intermediate filaments. Sequential extraction procedures shows that the FS polypeptides recognized by MAb 4F7 are exposed after treatment with 8 M urea. 4F7 immunoreactivity is lost after treatment with high ionic solutions (NaCl, KCl, KI). Immunogold electron microscopy reveals that this protein is present throughout the FS. This FS antigenic determinant first accumulates in an FS proximal body in late spermatids, then in granules extending distally along the flagellum. Staining of spermatozoa with flagellar dysgenesis reveals that this FS protein co-localizes with actin no matter what the location of their abnormal assembly. These data suggest that the transient microtubule-like spindle-shaped body of as yet unknown function could be involved in FS protein deposition and that the assembly of the FS and actin could be under the control of some common morphogenetical factor(s). MAb 4F7 should allow further investigations of this peri-axonemal structure in both normal and pathological conditions. (J Histochem Cytochem 45:909-922, 1997) Key Words: actin, cytoskeleton, flagellum, intermediate filaments, spermatogenesis, human spermatozoa
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