Fig. 1

 Cross-species regulatory activity of the C. robusta and D. rerio Hox5 and Otx CNEs. (A) Representation of the C. robusta Hox5 CNE expression in the most anterior part of the tail neural tube at larva stage. (B) The D. rerio Hoxa5a CNE shows well defined expression profile in the anterior part of the Ciona neural tube in a pattern reminiscent that of the Ciona Hox5 CNE (black arrowheads). (C) Representation of the C. robusta Otx CNE-B expression in the sensory vesicle(black arrow). (D) The D. rerio Otx CNE-B shows expression in the sensory vesicle (black arrow) and extends posteriorly along the visceral ganglion (black arrowhead). (E) C. robusta Otx CNE-B is active in a D. rerio transgenic embryo at 72 hpf. GFP signal (green) is visible in Te (white arrowhead), RGC (white arrow) and MB (orange arrowhead). As control, RFP expression (red) in muscles under the control of cardiac actin promoter. Diffuse GFP signal in the yolk is unspecific (asterisk). (F) Schematic representation of the D. rerio Otx1 gene endogenous expression at 72 hpf. Otx1 is expressed in RGCs, Te, D, MB and HB. Abbreviations: D, diencephalon; HB, hindbrain; MB, midbrain; RGC, retinal ganglion cells; Te, telencephalon. A-E Ciona embryos at larva stage. B, dorsal view; A,C-F, lateral view, anterior is on the left.