Takeuchi Masaki    Department   Kawasaki University of Medical Welfare  ,    Position   Associate Professor
Article types	原著
Language	English
Peer review	Peer reviewed
Title	Germ layer patterning in bichir and lamprey; an insight into its evolution in vertebrates
Journal	Formal name：Developmental biology Abbreviation：Dev Biol ISSN code：00121606/1095564X
Volume, Issue, Page	332(1),pp.90-102
Author and coauthor	Masaki Takeuchi, Maiko Takahashi, Masataka Okabe, Shinichi Aizawa
Authorship	Lead author
Publication date	2009/08
Summary	Amphibian holoblastic cleavage in which all blastomeres contribute to any one of the three primary germ layers has been widely thought to be a developmental pattern in the stem lineage of vertebrates, and meroblastic cleavage to have evolved independently in each vertebrate lineage. In extant primitive vertebrates, agnathan lamprey and basal bony !shes also undergo holoblastic cleavage, and their vegetal blastomeres have been generally thought to contribute to embryonic endoderm. However, the present marker analyses in basal ray-!nned !sh bichir and agnathan lamprey embryos indicated that their mesoderm and endoderm develop in the equatorial marginal zone, and their vegetal cell mass is extraembryonic nutritive yolk cells, having non-cell autonomous meso-endoderm inducing activity. Eomesodermin (eomes), but not VegT, orthologs are expressed maternally in these animals, suggesting that VegT is a maternal factor for endoderm differentiation only in amphibian. The study raises the viewpoint that the lamprey/bichir type holoblastic development would have been ancestral to extant vertebrates and retained in their stem lineage; amphibian-type holoblastic development would have been acquired secondarily, accompanied by the exploitation of new molecular machinery such as maternal VegT.
DOI	doi:10.1016/j.ydbio.2009.05.543
Document No.	19433081