The Spemann organizer meets the anterior-most neuroectoderm at the equator of early gastrulae in amphibian species.
Bottom Line: However, we found that this physical contact was already established at the equatorial region of very early gastrula in a wide variety of amphibian species.After the contact is established, the dorsal axis is formed posteriorly, but not anteriorly.The model also implies the possibility of constructing a common model of gastrulation among chordate species.
Affiliation: JT Biohistory Research Hall, 1-1 Murasaki-cho, Takatsuki, Osaka, 569-1125, Japan; Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan.Show MeSH
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Mentions: To observe the internal morphology of the embryos after physical contact was established, we fixed the embryos at ACE and cut them along the mid-sagittal plane (Fig.2A–F,I–K). Figure2 shows that the leading edge is located at the equatorial region in all the embryos. This suggests that the prospective head neuroectoderm is located at the equatorial region at ACE. If this were so, the ectoderm associated with the leading edge around the dorsal equatorial region at ACE would end up as the anterior-most neural tissue, such as the forebrain. To confirm this possibility, we labeled the dorsal equatorial region (tissue precisely lined by the leading edge) of C. pyrrhogaster at ACE, and examined whether the labeled tissue contributes to the anterior portion of the neural plate. As a result, the labeled cells (Fig.3A) were found in the anterior-most neural plate (Fig.3B). In combination with our previous result (Koide et al. 2002), it seems that the ectodermal layer on the equator at ACE corresponds to the prospective head neuroectderm both in anuran and urodele species.
Affiliation: JT Biohistory Research Hall, 1-1 Murasaki-cho, Takatsuki, Osaka, 569-1125, Japan; Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan.