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Fig. 3. Dominant-negative Xath5 inhibits proneural function of ato-related bHLH factors. mRNA for indicated transcription factor(s) was co-injected into 1 cell of 2-cell stage embryos with mRNA encoding β-galactosidase (β-gal) or GFP. Arrowheads indicate endogenous expression of indicated genes visualized by whole mount in situ hybridization. Xath5 (A), XNeuroD (C), Xath3 (E) and X-Ngnr-1 (G) induce ectopic neurogenesis, indicated by visualization of ectopic N-tubulin (A, C, E) or XNeuroD (G) (ectopic expression indicated by brackets). The proneural activity of these bHLH factors is blocked by co-injection of Xath5EnR (B, D, F, H). However, proneural activity of Xash3, indicated by increased X-Delta-1 expression on the injected side (I), is not inhibited by Xath5EnR co-injection (J), while the ability of XNeuroD to induce expression of X-Delta-1 (K) is efficiently suppressed by coexpression of Xath5EnR (L). Injection of Xath5EnR alone suppresses primary neurogenesis on the injected side (bracket in M) but does not disrupt expression of the neural plate marker Sox2 (N). Panels (A) and (K) are dorsal views with anterior to the top. Panels (I) and (J) are anterior views with dorsal to the top. Injected side is on the right in all images, and pink staining (B, F, N) and light blue staining (D) denote expression of β-gal injection tracer.
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