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Immunochemical characterization of a human sperm fibrous sheath protein, its developmental expression pattern, and
D Escalier1, J M Gallo, J Schrével
1Laboratoire de Biologie de la Reproduction et du Développement, CHU Bicêtre, Le Kremlin Bicêtre, France.
Abstract:
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 M(r) 95 x 10(3) 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, Kl). 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 colocalizes 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.
Insights
Monoclonal antibody 4F7 identifies a specific protein in the fibrous sheath (FS) of human sperm. This protein
Area of Science:
- Reproductive Biology
- Cell Biology
- Immunology
Background:
- The sperm fibrous sheath (FS) is a critical peri-axonemal structure.
- Understanding the molecular composition of the FS is essential for reproductive health research.
Purpose of the Study:
- To characterize a novel antigen recognized by monoclonal antibody (MAb) 4F7 in human sperm.
- To investigate the localization and potential function of this FS protein.
Main Methods:
- Western blotting using human sperm extracts.
- Immunogold electron microscopy.
- Analysis of spermatozoa with flagellar dysgenesis.
Main Results:
- MAb 4F7 specifically binds to two polypeptides (approx. 95 kDa) in the human sperm FS.
- This protein is localized throughout the FS and shows dynamic accumulation during spermatid development.
- The FS protein colocalizes with actin, suggesting a shared regulatory mechanism.
Conclusions:
- MAb 4F7 is a valuable tool for studying the sperm FS.
- A transient spindle-shaped body may be involved in FS protein deposition.
- Common factors might regulate the assembly of the FS and actin.