Conserved and divergent expression patterns of markers of axial development in the laboratory opossum, Monodelphis domestica.
Previous comparative studies suggest that the requirement for Nodal in epiblast and hypoblast development is unique to mammalians. Expression of anterior visceral endoderm (AVE) genes in the visceral endoderm and of their orthologs in the hypoblast may be unique to mammalians and avians, and is absent in the reptilian hypoblast. Axis formation in reptiles is signaled by the formation of the posterior marginal epiblast (PME), which expresses a series of primitive streak genes. To assess the phylogenetic origin of Nodal and AVE gene expression and axis formation in amniotes, we examined marker gene expression in gray short-tailed opossum, a metatherian.



Nodal was expressed in neither epiblast nor hypoblast of opossum embryos. No AVE genes were expressed in the opossum hypoblast. Attainment of polarity in the embryonic disk was signaled by Nodal, Wnt3a, Fgf8, and Bra expression in the PME at 8.5 days post-coitus.



Nodal expression in epiblast or hypoblast may be unique to eutherians. AVE gene expression in visceral endoderm and hypoblast may have been independently acquired in eutherian and avian lineages. PME formation appears to be the event that signals axis formation in reptilian and metatherian embryos, and thus may be an ancestral characteristic of basal amniotes. Developmental Dynamics 245:1176-1188, 2016. © 2016 Wiley Periodicals, Inc.
Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, Kobe, Japan.
Michio
M
Yoshida
Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, Kobe, Japan.
Eriko
E
Kajikawa
Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, Kobe, Japan.
Daisuke
D
Yamamoto
Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, Kobe, Japan.|Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo, Kanagawa, Japan.
Daisuke
D
Kurokawa
Ultrastructural Research Team, Biosystem Dynamics Group, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies (CLST), Kobe, Japan.
Shigenobu
S
Yonemura
Laboratory for Animal Resources and Genetic Engineering, Center for Developmental Biology (CDB), RIKEN Kobe, Kobe, Japan.
Kensaku
K
Kobayashi
Laboratory for Animal Resources and Genetic Engineering, Center for Developmental Biology (CDB), RIKEN Kobe, Kobe, Japan.
Hiroshi
H
Kiyonari
Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, Kobe, Japan.|Laboratory for Animal Resources and Genetic Engineering, Center for Developmental Biology (CDB), RIKEN Kobe, Kobe, Japan.
Shinichi
S
Aizawa
D000818:Animals; D019521:Body Patterning / Q000235:genetics / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D048309:Monodelphis / Q000145:classification / Q000196:embryology* / Q000378:metabolism*; D055457:Nodal Protein / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny
D055457:Nodal Protein
AVE gene; Nodal; axis formation; hypoblast; metatherian; posterior marginal epiblast (PME)