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Fig. 1 Detailed analysis of gene expression at early NPB stages. A-P: Lateral views of wild type embryos with dorsal toward the right and anterior toward the top. A: Schematic of the approximate location of the NPB, between dorsal neural ectoderm and ventral epidermal ectoderm, in gastrula stage zebrafish embryos. B-F: dlx3b expression from 70% epiboly through 2 somites. dlx3b transcripts are found throughout the epidermal ectoderm at 70% epiboly (B), 80% epiboly (C), and 90% epiboly (D). At tail bud, the expression domain narrows to a more discrete domain near the NPB (E), and at 2 somites the posterior portion of this domain is mostly gone (F). G-K: prdm1a expression. prdm1a transcripts are found at the NPB at each of these stages, but the domain narrows and moves toward the dorsal midline over time. Strong expression is also evident in the prechordal plate at the anterior tip of the embryo. L-P: gbx1 is expressed in dorsal neural tissue, and its domain shifts toward the future anterior as development proceeds. A was modified from Kimmel et al. ([1995]), with permission from the publisher.