Expression of the G-protein α-subunit gustducin in mammalian spermatozoa
Dorke Meyer1, Johanna Fehr1, Heike Borth1, Patricia Widmayer2, Beate Wilhelm3, Thomas Gudermann1 & Ingrid Boekhoff1
The G protein subunit α-gustducin is generally accepted as a marker for chemosensitive cells. Since chemosensation is especially important for the navigation of sperm towards the egg, attempts were made to explore whether α-gustducin might also be expressed in spermatozoa. RT-PCR experiments revealed that a gustducin PCR specific RNA fragment with the predicted size could be amplified from total mouse and rat testis. To identify the testicular cell type in which α-gustducin is expressed, immunohistochemical experiments were performed with an anti-gustducin-specific antibody. The most intense immunoreactivity was visible in differentiating spermatids localized in the lumen of the seminiferous tubules whereas no staining was detectable in spermatogonia. To verify whether α-gustducin is still expressed in mature spermatozoa, mouse and rat sperm were subjected to immunocytochemistry as well as electron microscopy. A strong staining of the innerdense fibres was obtained within the flagellum. Similarly, analyzing human sperm for α-gustducin staining also revealed a strong labeling of the midpiece of the flagellum whereas the principle piece remained unstained. The observation that α-gustducin is expressed in the tail of mammalian spermatozoa may now motivate to identify the corresponding signaling cascade, probably defining the functional role of α-gustducin in spermatozoa.