Abstract
AbstractGastrulation is a critical event whose molecular mechanisms are thought to be conserved among vertebrates. However, the morphological movement during gastrulation appears to be divergent across species, making it difficult to discuss the evolution of the process. Previously, we proposed a novel amphibian gastrulation model, the “subduction and zippering (S&Z) model”. In this model, the organizer and the prospective neuroectoderm are originally localized in the blastula’s blastocoel roof, and these embryonic regions move downward to make physical contact of their inner surfaces with each other at the dorsal marginal zone. The developmental stage when contact between the head organizer and the anterior-most neuroectoderm is established is called “anterior contact establishment (ACE).” After ACE, the A-P body axis elongates posteriorly. According to this model, the body axis is derived from limited regions of the dorsal marginal zone at ACE. To investigate this possibility, we conducted stepwise tissue deletions using Xenopus laevis embryos and revealed that the dorsal one-third of the marginal zone had the ability to form the complete dorsal structure by itself. Furthermore, a blastocoel roof explant of the blastula, which should contain the organizer and the prospective neuroectoderm in the S&Z model, autonomously underwent gastrulation and formed the complete dorsal structure. Collectively, these results are consistent with the S&Z gastrulation model and identify the embryonic region sufficient for construction of the complete dorsal structure. Finally, by comparing amphibian gastrulation to gastrulation of protochordates and amniotes, we discuss the gastrulation movement evolutionarily conserved among chordates.
Publisher
Springer Science and Business Media LLC
Subject
Developmental Biology,Genetics
Reference37 articles.
1. Ariizumi T, Sawamura K, Uchiyama H, Asashima M (1991) Dose and time-dependent mesoderm induction and outgrowth formation by activin A in Xenopus laevis. Int J Dev Biol 35(4):407–414
2. Asashima M, Nakano H, Shimada K, Kinoshita K, Ishii K, Shibai H, Ueno N (1990) Mesodermal induction in early amphibian embryos by activin A (erythroid differentiation factor). Roux’s Arch Dev Biol : Off Organ EDBO 198(6):330–335. https://doi.org/10.1007/BF00383771
3. Cho KW, Blumberg B, Steinbeisser H, De Robertis EM (1991) Molecular nature of Spemann’s organizer: the role of the Xenopus homeobox gene goosecoid. Cell 67(6):1111–1120. https://doi.org/10.1016/0092-8674(91)90288-a
4. Clevers H, Nusse R (2012) Wnt/β-catenin signaling and disease. Cell 149(6):1192–1205. https://doi.org/10.1016/j.cell.2012.05.012
5. Connolly DJ, Patel K, Cooke J (1997) Chick noggin is expressed in the organizer and neural plate during axial development, but offers no evidence of involvement in primary axis formation. Int J Dev Biol 41(2):389–396