Fig. 5

HH signaling is necessary for epidermal morphogenesis.

(A) In heat-shocked control fish the epidermis (labeled by cldnb:EGFP, green) was folded around the posterior margin of individual scales (marked by ARS, magenta). (A’) orthogonal projection, arrow indicates leading edge of epidermis; n = 8. (B) Heatshock induction of a dominant repressor Gli2 (hs:gli2-DR), completely blocked epidermal folding. (B’) Orthogonal view; n = 12. (C) HH-responding cells (cyan) were very few at early stages of scale development (papilla) labelled by sp7:EGFP (yellow). HH-responding cells were found posterior and deep to the extending scale (extension) and persisted throughout later scale growth (imbrication); n = 8. (D) HH-responding cells (cyan) appeared prior to epidermal invagination (pre). Initial invagination (arrow), followed the contour of the HH responding population (initial). Epidermal invagination continued in close association with HH responding cells (final); n = 8. (E) High resolution imaging of the leading row of invaginating epidermal cells revealed hallmarks of cell migration including membrane ruffles (arrows) and long cellular extensions (arrow head); n = 10. (F) Shha overexpression by heatshock induction of hs:shha lead to severe kyphosis; n = 48. (G) cldnb:EGFP+ epidermis in hs:shha larvae migrated from the animal onto the glass coverslip during image acquisition; n = 6. Scale bars, 100 µm (A,B); 50 µm (C); 25 µm (D); 10 µm (E); 1 mm (F); 100 µm (G); 20 µm (G, inset).