Fig. 4.

Effects of retinoic acid (RA) signaling alterations on the development of ectodermal sensory neurons (ESNs) in amphioxus. a–d′ Larvae at 36 hpf (hours post fertilization) were stained for glutamate-immunoreactivity (GLU-ir, green), acetylated tubulin-ir (AT-ir, red), and with the nucleic acid dye Hoechst (blue). e–h′ Schematic drawings of the animals shown in a–d′. Outlines of the animals and their pre-oral pits are depicted in grey, the gut in bright yellow, and neural projections in red. ESNs are depicted as circles with a red outline that are filled with either green or yellow color to represent the presence or absence of GLU-ir, respectively. Animals had been treated with either DMSO (control, a, a′, e, e′), with the RA receptor (RAR) antagonist BMS493 (b–d, f–h), or with all-trans RA (b′–d′, f′–h′), starting from different treatment time points (t), at either 6, 12 or 24 hpf, as indicated. i Statistical analyses of the observed effects of RA signaling alterations on ESN formation. Colored bars depict the average number of ESNs in the whole ectoderm (all) or in specific ectodermal sections along the anterior–posterior axis. The image below the first diagram shows Hoechst labeling (grey) in a larva at 36 hpf, with dotted lines marking the sections of the ectoderm (posterior, middle, anterior), in which ESNs were counted. Green bars stand for control animals, blue bars for animals treated with BMS493, and red bars for animals treated with all-trans RA. For each diagram, treatment time points (t), at 6, 12 or 24 hpf, are given in the upper right corner and the number (n) of animals counted per condition is indicated at the base of the first three colored bars. Error bars depict the standard deviation (σ). An asterisk (*) above an error bar indicates that the difference between this condition and the corresponding control is statistically significant. The scale bar in a also applies to b–d, a′–d′, and the scale bar in e also applies to f–h, e′–h′