Xenbase Image ID: 171267

Supplementary Figure 6. Timing of Nodal/Activin signal requirement for neural induction. a, Expression of Neurogenin at the N2 stage in embryos after continuous treatment with Activin or SB505124 from 3 hpf, 4 hpf, 5 hpf or 7 hpf at 19°C. b, Expression of Neurogenin in G4 and N2 stage embryos after treatment with Activin or SB505124 between 3 hpf and 4 hpf or between 3 hpf and 6 hpf at 19°C. c, Expression of Neurogenin in G4 and N2 control embryos. d, Drawing of amphioxus embryos at the stages at which treatments were performed, adapted from Conklin. When two pictures are presented, the left one is side view with anterior to the left and dorsal to the top whereas the right picture is dorsal view with anterior to the left. Blue arrows correspond to the period of treatment. Our results show that inhibiting the Nodal/Activin pathway via the application of SB505124 at any time between cleavage stage and G1 stage impeded the formation of Neurogenin positive neural tissue (a, cd). Moreover, one-hour treatment between cleavage stage and morula stage was also sufficient to preclude neural tissue formation (b, c-d). Conversely, treatment with Activin between cleavage stage and the beginning of gastrulation (G0-G1 stage) induced neural commitment in the whole ectoderm at G4, although neural fate was lost in the anterior region at N2 (b, c-d). In contrast, activating the Nodal/Activin pathway after the morula stage was not sufficient to neuralize all ectodermal cells (a, c-d). Altogether these results suggest that Nodal/Activin signal is required very early for neural induction to occur, and that the maintenance of the neural fate in the anterior region is also dependent upon this signal. Image published in: Le Petillon Y et al. (2017) Image downloaded from an Open Access article in PubMed Central. Image reproduced on Xenbase with permission of the publisher and the copyright holder. Larger Image Printer Friendly View

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