title: Expression of Smac/DIABLO in mouse preimplantation embryos and its correlation to apoptosis and fragmentation.
abstract: Regulation of early embryonal development during fertilization and implantation is crucial for mammalian reproduction. Several studies have described cell death during preimplantation embryogenesis in a range of mammalian species, both in vivo and in vitro. Therefore, apoptosis may be involved in early embryonic arrest and the characteristic cytoplasmic fragments are the equivalents of apoptotic bodies, the end-product of apoptosis. Although apoptosis is expected to associate with fragmentation in early preimplantation embryos, the mechanism through which this fragmentation occurs has not been elucidated. Recently, second mitochondria-derived activator of caspase/Direct IAP Binding Protein with Low pI (Smac/DIABLO) was identified as a mitochondrial protein that is released into the cytosol during apoptosis. Once released, the Smac/DIABLO blocks the anti-apoptotic activity of inhibitor of apoptosis proteins (IAPs). We hypothesized that the Smac/DIABLO may be involved in the fragmentation of mouse preimplantation embryos. Therefore, we investigated the expression of Smac/DIABLO mRNA and protein and its localization in mouse oocytes and preimplantation embryos. Smac/DIABLO mRNA was detected by RT-PCR in the oocytes and the preimplantation embryos. Immunohistochemistry studies showed that the Smac/DIABLO protein localized in mitochondria and was released into the cytosol in both fragmented embryos and embryos in which apoptosis was induced by staurosporine. These observations indicate that the Smac/DIABLO is involved in the fragmentation and apoptosis of preimplantation embryos.
authors.affiliation: Division of Obstetrics and Gynecology, Department of Reproductive and Developmental Medicine, Akita University School of Medicine, 1-1-1, Hondo, Akita 010-8543, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Honda
authors.forename: Hideo
authors.initials: H
authors.lastname: Tanikawa
authors.forename: Jun
authors.initials: J
authors.lastname: Fukuda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kawamura
authors.forename: Naoki
authors.initials: N
authors.lastname: Sato
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Sato
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Hideya
authors.initials: H
authors.lastname: Kodama
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001755:Blastocyst / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D045304:Cytochromes c / Q000032:analysis / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D047108:Embryonic Development; D051034:Inhibitor of Apoptosis Proteins; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C499605:Diablo protein, mouse; D051034:Inhibitor of Apoptosis Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D012333:RNA, Messenger; D045304:Cytochromes c; D019311:Staurosporine