Fig. 1. Dlx gene expression becomes restricted to the ventral ectoderm. (A) At blastula stage (stage 9), Xdlx3 is expressed broadly throughout the ectoderm. Animal pole is oriented up. (B) By early gastrula stage (stage 10), Xdlx3 expression is restricted to the more ventral ectoderm (black arrowhead). Lateral view with dorsal oriented to the left. Dorsal lip is on the left (green arrowhead). (C) By the beginning of neurulation (stage 13), Xdlx3 expression is completely absent from the neural plate and is expressed throughout the non-neural ectoderm (dorsal view with anterior to the top). (D) Schematic of Dlx homeodomain constructs. The activating Dlx construct was made by ligating regions encoding the Dlx3 homeodomain (blue) to the VP16 activation domain (yellow). A conditional version was generated by fusion to the ligand-binding domain of the human glucocorticoid receptor (GR; green). Inhibitory constructs were made similarly using the Engrailed repressor domain (EnR; red). Identical constructs were made with the Dlx5 homeodomain. The homeodomains are highly conserved among Dlx family members; thus the fusion proteins are envisaged to regulate target genes of all family members comparably. See Materials and Methods for details of construct preparation.

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