title: Conserved and divergent expression patterns of markers of axial development in reptilian embryos: Chinese soft-shell turtle and Madagascar ground gecko.
abstract: The processes of development leading up to gastrulation have been markedly altered during the evolution of amniotes, and it is uncertain how the mechanisms of axis formation are conserved and diverged between mouse and chick embryos. To assess the conservation and divergence of these mechanisms, this study examined gene expression patterns during the axis formation process in Chinese soft-shell turtle and Madagascar ground gecko preovipositional embryos. The data suggest that NODAL signaling, similarly to avian embryos but in contrast to eutherian embryos, does not have a role in epiblast and hypoblast development in reptilian embryos. The posterior marginal epiblast (PME) is the initial molecular landmark of axis formation in reptilian embryos prior to primitive plate development. Ontogenetically, PME may be the precursor of the primitive plate, and phylogenetically, Koller's sickle and posterior marginal zone in avian development may have been derived from the PME. Most of the genes expressed in the mouse anterior visceral endoderm (AVE genes), especially signaling antagonist genes, are not expressed in the hypoblast of turtle and gecko embryos, though they are expressed in the avian hypoblast. This study proposes that AVE gene expression in the hypoblast and the visceral endoderm could have been independently established in avian and eutherian lineages, similar to the primitive streak that has been independently acquired in these lineages.
authors.affiliation: Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Kajikawa
authors.affiliation: Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan; Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo, 1024 Koajiro, Misaki, Miura, Kanagawa 238-0225, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kurokawa
authors.affiliation: Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Noro
authors.affiliation: Daiwa Youshoku LLC, 11-697 Oaza-itaya, Nishitaku, Taku, Saga 846-0041, Japan.
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Iwai
authors.affiliation: Ultrastructural Research Team, Biosystem Dynamics Group, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies (CLST), 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan.
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Yonemura
authors.affiliation: Laboratory for Animal Resources and Genetic Engineering, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: Laboratory for Animal Resources and Genetic Engineering, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kiyonari
authors.affiliation: Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan; Laboratory for Animal Resources and Genetic Engineering, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan. Electronic address: saizawa@cdb.riken.jp.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Aizawa
mesh_terms: D000818:Animals; D001756:Blastoderm / Q000502:physiology; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D047108:Embryonic Development; D004707:Endoderm / Q000378:metabolism; D054262:Gastrulation / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000502:physiology; D008116:Lizards / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D055457:Nodal Protein / Q000502:physiology; D010802:Phylogeny; D054240:Primitive Streak / Q000378:metabolism; D013045:Species Specificity; D014157:Transcription Factors / Q000502:physiology; D014426:Turtles / Q000196:embryology* / Q000235:genetics / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D055457:Nodal Protein; D014157:Transcription Factors
keywords: Axis formation; Chinese soft-shell turtle; Hypoblast; Madagascar ground gecko; Posterior marginal epiblast; Reptile