title: Possible involvement of CD81 in acrosome reaction of sperm in mice.
abstract: Tetraspanin CD81 is closely homologous in amino acid sequence with CD9. CD9 is well known to be involved in sperm-egg fusion, and CD81 has also been reported to be involved in membrane fusion events. However, the function of CD81 as well as that of CD9 in membrane fusion remains unclear. Here, we report that disruption of the mouse CD81 gene led to a reduction in the fecundity of female mice, and CD81-/- eggs had impaired ability to fuse with sperm. Furthermore, we demonstrated that when CD81-/- eggs were incubated with sperm, some of the sperm that penetrated into the perivitelline space of CD81-/- eggs had not yet undergone the acrosome reaction, indicating that the impaired fusibility of CD81-/- eggs may be in part caused by failure of the acrosome reaction of sperm. In addition, we showed that CD81 was highly expressed in granulosa cells, somatic cells that surround oocytes. Our observations suggest that there is an interaction between sperm and CD81 on somatic cells surrounding eggs before the direct interaction of sperm and eggs. Our results may provide new clues for clarifying the cellular mechanism of the acrosome reaction, which is required for sperm-egg fusion.
authors.affiliation: Department of Reproductive Biology and Pathology, National Center for Child Health and Development, Tokyo, Japan.
authors.forename: Maya
authors.initials: M
authors.lastname: Tanigawa
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Miyamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sato
authors.forename: Hidenori
authors.initials: H
authors.lastname: Akutsu
authors.forename: Masaru
authors.initials: M
authors.lastname: Okabe
authors.forename: Eisuke
authors.initials: E
authors.lastname: Mekada
authors.forename: Keiichi
authors.initials: K
authors.lastname: Sakakibara
authors.forename: Mami
authors.initials: M
authors.lastname: Miyado
authors.forename: Akihiro
authors.initials: A
authors.lastname: Umezawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Miyado
mesh_terms: D020101:Acrosome Reaction / Q000235:genetics*; D000818:Animals; D015703:Antigens, CD / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000235:genetics; D007247:Infertility, Female / Q000235:genetics*; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D006080:Ovarian Follicle / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism*; D060225:Tetraspanin 28; D060245:Tetraspanin 29
chemical_list: D015703:Antigens, CD; C554799:Cd81 protein, mouse; C554870:Cd9 protein, mouse; D008562:Membrane Glycoproteins; D060225:Tetraspanin 28; D060245:Tetraspanin 29