Integrins are not involved in the process of human sperm-oolemmal fusion |
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Authors: | Sengoku Kazuo Takuma Naoyuki Miyamoto Toshinobu Horikawa Michiharu Ishikawa Mutsuo |
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Affiliation: | Department of Obstetrics and Gynecology, Asahikawa Medical College, Midorigaoka-higashi 2-1, Asahikawa, 0788510, Japan |
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Abstract: | BACKGROUND: We investigated whether integrins are required forthe human spermoocyte binding and fusion processes. METHODS:The expression of several integrin subunits at the human oocyteplasma membrane was investigated using immunofluorescence microscopy,and the functional role of integrins expressed at the humanoocyte surface in spermoocyte interaction was studiedusing a zona-free human oocyte binding and fusion assay. A totalof 144 unfertilized oocytes were stained with anti-integrinantibodies and 147 zona-free unfertilized oocytes were inseminatedin the presence of various anti-integrin antibodies that wereexpressed in oocyte plasma membrane. RESULTS: The antibodiesof six integrin subunits (2, 3, 5, 6, V, M) and six integrinsubunits (1, 2, 3, 4, 5, 6) were bound to the surface of fixedunfertilized oocytes. In contrast, the presence of 1 and 4 subunitscould not be verified. The human spermoocyte bindingwas only partially inhibited by blocking antibodies of 2, 3,5, 6, V, M, 1, 2 and 3 with a maximum of 55% inhibition, butantibodies of 4, 5 and 6 showed no effect on spermoolemmalbinding. A similar reduction of the number of fused sperm wasobserved. However, the ratio of fused sperm to total sperm (boundand fused) was not impaired by all integrin antibodies, suggestingthat integrins had no role in the spermoolemmal fusionprocess. CONCLUSIONS: These results suggest that one of thebinding mechanisms can be inhibited by integrin antibodies butthat this mechanism does not play an essential role in the humanspermoolemmal binding and fusion processes. The othermechanisms, insensitive to integrins, may involve both bindingand fusion processes in human oocytes. |
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Keywords: | human gamete fusion/integrin/oocyte plasma membrane/sperm |
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