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Figure S7. Models of placode specification. A: The “neural plate border state model” proposes that PPE (red) and NC (blue) are induced from a common precursor (purple) at the neural plate border, whereas the “binary competence model” proposes that they are induced from non-neural (yellow) and neural (green) ectodermal competence territories, respectively. B: In a new model that combines aspects of both these models, we propose here that there is indeed an NPB region during gastrulation, which gives rise to both PPE and NC. However, the NPB domain is not defined by a unique regulatory state but rather by the overlap of dorsally restricted neural (green) and ventrally restricted non- neural (yellow) competence factors (left panel; region of overlap: olive green). The degree of overlap decreases during gastrulation resolving into mutually exclusive non-neural and neural competence territories at the end of gastrulation (middle panel). Inducing signals from adjacent tissues induce preplacodal ectoderm (FGF, BMP-inhibitors, Wnt-inhibitors; red) and neural crest (FGF, BMP, Wnt; blue) at the border of non-neural and neural ectoderm, respectively (from [2]; modified from [70]). (PDF 2779 kb) Image published in: Maharana SK and Schlosser G (2018) © Schlosser et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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