title: De novo formation of nucleoli in developing mouse embryos originating from enucleolated zygotes.
abstract: The large, compact oocyte nucleoli, sometimes referred to as nucleolus precursor bodies (NPBs), are essential for embryonic development in mammals; in their absence, the oocytes complete maturation and can be fertilized, but no nucleoli are formed in the zygote or embryo, leading to developmental failure. It has been convincingly documented that zygotes inherit the oocyte nucleolar material and form NPBs again in pronuclei. It is commonly accepted that during early embryonic development, the original compact zygote NPBs gradually transform into reticulated nucleoli of somatic cells. Here, we show that zygote NPBs are not required for embryonic and full-term development in the mouse. When NPBs were removed from late-stage zygotes by micromanipulation, the enucleolated zygotes developed to the blastocyst stage and, after transfer to recipients, live pups were obtained. We also describe de novo formation of nucleoli in developing embryos. After removal of NPBs from zygotes, they formed new nucleoli after several divisions. These results indicate that the zygote NPBs are not used in embryonic development and that the nucleoli in developing embryos originate from de novo synthesized materials.
authors.affiliation: Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan Laboratory for Genomic Reprogramming, Center for Developmental Biology, RIKEN, Kobe 650-0047, Japan Laboratory for Chromosome Segregation, Center for Developmental Biology, RIKEN, Kobe 650-0047, Japan kyogoku@cdb.riken.jp.
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Kyogoku
authors.affiliation: Department of Biology of Reproduction, Institute of Animal Science, Prague 104 00, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Fulka
authors.affiliation: Laboratory for Genomic Reprogramming, Center for Developmental Biology, RIKEN, Kobe 650-0047, Japan Faculty of Life and Environmental Sciences, University of Yamanashi, Kofu 400-8501, Japan.
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Wakayama
authors.affiliation: Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyano
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000166:cytology; D002455:Cell Division; D002466:Cell Nucleolus / Q000502:physiology*; D054885:Cumulus Cells / Q000166:cytology; D046149:Embryo Culture Techniques; D004624:Embryo Transfer; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008813:Mice, Inbred ICR; D008846:Micromanipulation; D041681:NIH 3T3 Cells; D009865:Oocytes / Q000166:cytology; D011247:Pregnancy; D015053:Zygote / Q000254:growth & development*
keywords: Embryo; Mouse; Nucleolus; Oocyte