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Identification of a protein in the fibrous sheath of the sperm flagellum
B A Fenderson1, K Toshimori, C H Muller
1Division of Biochemical Oncology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Abstract:
The fibrous sheath is a unique cytoskeletal component in the principal-piece segment of the mammalian sperm flagellum. Monoclonal antibody ATC was shown by indirect immunofluorescence (IIF) to bind to the principal piece of the flagellum of permeabilized mouse, rat, and hamster sperm, but not to that region of guinea pig, rabbit, or human sperm. IIF on isolated fibrous sheaths confirmed that the antigen was present in the fibrous sheath of mouse, rat, and hamster sperm. On Western blots of mouse spermatozoa, ATC identified a relatively insoluble major antigen with an apparent molecular weight of 67,000 (Mr 67,000). Hamster sperm fibrous sheaths contain an antigen of Mr 66,000, while rat sperm fibrous sheaths contain an antigen of Mr 65,500. The antigen was first detected in late spermatids, as determined by immunohistochemical procedures on sections of mouse, rat, and hamster testis. The antigen was not detected on Western blots of mouse brain, kidney, liver, or thymus. These results indicate that ATC recognizes a protein integral to the fibrous sheath of the principal piece of sperm detected by immunohistochemistry late in spermiogenesis that is probably restricted to the male germ cell line.
Insights
Monoclonal antibody ATC identifies a fibrous sheath protein in mammalian sperm. This protein is crucial for sperm flagellum function and is specific to the male germline.
Area of Science:
- Spermatozoa biology
- Cytoskeletal proteins
- Mammalian reproduction
Background:
- The fibrous sheath is a critical cytoskeletal structure in the principal piece of the mammalian sperm flagellum.
- Understanding the molecular composition of the fibrous sheath is essential for reproductive biology.
Purpose of the Study:
- To characterize a novel antigen recognized by monoclonal antibody ATC within the mammalian sperm fibrous sheath.
- To determine the species-specific distribution and developmental expression of this fibrous sheath antigen.
Main Methods:
- Indirect immunofluorescence (IIF) on permeabilized sperm and isolated fibrous sheaths.
- Western blotting of spermatozoa and various tissue extracts.
- Immunohistochemistry on testicular sections.
Main Results:
- Monoclonal antibody ATC binds to the principal piece of the flagellum in mouse, rat, and hamster sperm, but not in guinea pig, rabbit, or human sperm.
- Western blots revealed a major insoluble antigen of approximately 67,000 Mr in mouse sperm, with similar antigens of 66,000 Mr in hamster and 65,500 Mr in rat sperm.
- Immunohistochemistry indicated the antigen's presence in late spermatids, suggesting its role during spermiogenesis and its restriction to the male germ cell line.
Conclusions:
- Monoclonal antibody ATC recognizes a specific protein integral to the fibrous sheath of mammalian sperm.
- This fibrous sheath protein is expressed late in spermiogenesis and appears to be specific to male germ cells.
- The findings contribute to understanding sperm structure-function relationships and male fertility.