2°NC cells turn off sox10 expression upon migration into the eye.

(A-C) in situ gene expression analysis of sox10 (A), pitx2 (B) and foxc1a (C) in WT embryos at 28 hpf. Arrows indicate peri-ocular mesenchymal cells. Scale bar: 50 μm. (D-H’) Photoconversion of mem-tdEosFP and recovery of green fluorescence for visualization of de novo sox10 reporter expression. At the indicated stages, mem-tdEosFP was switched from green to red (magenta) by illumination with 400-nm light (D-H). Continued mem-tdEosFP expression was scored by reappearance of green fluorescence at 36 hpf (D’-H’). Recovery of green mem-tdEosFP fluorescence in the eye at 36 hpf was noticed in embryos photoconverted until 20 hpf (D-F’). Photoconversion at 22 or 24 hpf showed recovery of green fluorescence in the head but not in the eye region (G’-H’), indicating that 2°NC cell derivatives which have migrated into the eye have turned off sox10 transgene expression by 22 hpf. In contrast, sox10 reporter expression in NC derivatives has ceased in the pharyngeal arches at 16 hpf (asterisks, A’) as well as in 1°NC on the proximal side of the retina. Green NC cells in panel E (white arrow) are un-photoconverted cells. Scale bar: 40 μm. (PDF)