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Fig. 3 Regulatory elements of dlx1a/2a and dlx2b drive reporter gene expression in the zebrafish forebrain and branchial arches. A: Genomic organization of the dlx1a/dlx2a and of the dlx2b loci. Exons are represented in white and untranslated regions in black. Intergenic regulatory elements are shown as blue (URE2 and I12b) and red boxes (I56i and I56ii). The dlx2bDRE is shown as a purple box. B: Schematic representation of the transgene constructs (containing the β-globin minimal promoter [gray] linked to GFP [green]) used to generate transgenic zebrafish. The Tg(dlx1a/2aIG:GFP) construct contains a 6 kb of the intergenic fragment from the dlx1a/dlx2a intergenic region, the Tg(URE2dlx1a/2a:GFP) contains a 900-bp fragment encompassing the URE2 enhancer and the Tg(dlx2bDRE:GFP) contains a 200-base pair fragment downstream of dlx2b. C-K: Activity of the transgene constructs in the forebrain at 24 hours postfertilization (hpf) and 48 hpf Tg(URE2dlx1a/2a:GFP) transgene (C-E), Tg(dlx1a/2aIG:GFP) transgene (F-H), and Tg(dlx2bDRE:GFP) (I-K). tel, telencephalon; di, diencephalon; md, mandibular portion of branchial arches; GFP, green fluorescent protein. Scale bar = 100 μm.