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Microtubule-associated epithelial protein E-MAP-115 is localized in the spermatid manchette
Tarja-Leena Penttilä1, Martti Parvinen, Jorma Paranko
1Department of Anatomy, Institute of Biomedicine, University of Turku, Finland.
Abstract:
A microtubule-associated protein E-MAP-115 has been originally isolated and characterized from HeLa cells. Because of its predominant expression in cultured cells of epithelial origin, it has been suggested to be involved in the regulation of cell polarization. The present immunocytochemical, Northern blot and in situ hybridization analysis of E-MAP-115 in the mouse and rat seminiferous epithelium indicates its distinct association with the spermatid manchette, a unique microtubular structure which appears in the cytoplasm of spermatids at step 8 when nuclear polarization and elongation starts. At steps 15-16 when manchette has been disassembled, immunoreactivity for E-MAP-115 disappeared. At immunoelectron microscopical level, E-MAP-15 was associated with the microtubules of the manchette. In the Western and Northern blot analysis, a distinct stage-dependent expression of a single E-MAP-115 polypeptide and two mRNA species (3.4 and 2.4 kb) could be identified. MTEST 60, a spermatid-specific transcript, showed a 100% homology over region of 68-193 bp of E-MAP-115 sequence. The reported specific localization of E-MAP-115 to the spermatid manchette strongly supports its role as a regulator of cell polarization. This, in turn, supports the hypotheses concerning the dynamic function of the manchette during spermiogenesis.
Insights
The microtubule-associated protein E-MAP-115 is specifically found in the spermatid manchette, a structure crucial for cell polarization during sperm development. Its presence supports the manchette's dynamic role in spermiogenesis.
Area of Science:
- Cell Biology
- Reproductive Biology
- Microtubule Dynamics
Background:
- Epithelial-cell-derived microtubule-associated protein E-MAP-115 was initially identified in HeLa cells.
- E-MAP-115's predominant expression in epithelial cells suggested a role in cell polarization regulation.
Purpose of the Study:
- To investigate the localization and expression of E-MAP-115 in the mammalian seminiferous epithelium.
- To determine the potential role of E-MAP-115 in spermiogenesis and cell polarization.
Main Methods:
- Immunocytochemistry and immunoelectron microscopy to detect E-MAP-115 localization.
- Northern blot and Western blot analyses to assess E-MAP-115 expression at mRNA and protein levels.
- In situ hybridization to analyze E-MAP-115 mRNA distribution.
Main Results:
- E-MAP-115 was distinctly localized to the spermatid manchette, a microtubular structure involved in nuclear polarization and elongation.
- E-MAP-115 expression was stage-dependent, appearing at step 8 and disappearing when the manchette disassembled.
- Analysis revealed a single E-MAP-115 polypeptide and two mRNA species (3.4 and 2.4 kb), with homology to the spermatid-specific transcript MTEST 60.
Conclusions:
- The specific localization of E-MAP-115 to the spermatid manchette supports its function as a regulator of cell polarization.
- These findings reinforce the hypothesis of the manchette's dynamic involvement in the complex process of spermiogenesis.