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Germ layer patterning in bichir and lamprey; an insight into its evolution in vertebrates.
- Source :
-
Developmental biology [Dev Biol] 2009 Aug 01; Vol. 332 (1), pp. 90-102. Date of Electronic Publication: 2009 May 09. - Publication Year :
- 2009
-
Abstract
- 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 fishes 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-finned fish 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.
- Subjects :
- Animals
Embryo, Nonmammalian cytology
Endoderm embryology
Fishes genetics
Gene Expression Regulation, Developmental
Lampreys genetics
Larva cytology
Mesoderm embryology
Models, Biological
Phylogeny
Reverse Transcriptase Polymerase Chain Reaction
Biological Evolution
Body Patterning
Fishes embryology
Germ Layers embryology
Lampreys embryology
Subjects
Details
- Language :
- English
- ISSN :
- 1095-564X
- Volume :
- 332
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Developmental biology
- Publication Type :
- Academic Journal
- Accession number :
- 19433081
- Full Text :
- https://doi.org/10.1016/j.ydbio.2009.05.543