Fig. 1

Basal epidermal shha and ptch2-defined responses in basal epidermis and pre-osteoblasts become progressively distally restricted during caudal fin development. (A-J’) Differential interference contrast and fluorescent overlay images of developing caudal fins of shha:GFP (A-D, I, I’) and ptch2:Kaede (E-H, J, J’) fish of indicated ages. White dotted lines outline the fin fold (A–F). The white arrowhead indicates the gap in melanophores where shha:GFP expression emerges. Yellow boxes in (I, J) indicate the 2x zoom fields in (I’, J’). White brackets (I-J’) mark branched reporter domains in dorsal rays 2 and 3 preceding overt ray branching. (K–P) Single optical slices of caudal fin dorsal ray 3 in longitudinal (K, M,O) and transverse (L, N, P) planes derived from 3D-reconstructed whole mount confocal images of fluorescent reporter fish of indicated ages. (K, L) 23 dpf shha:GFP fin whole mount antibody stained for GFP (green) and the basal epidermis marker Tp63 (magenta). The orange dashed line outlines a representative Tp63+, GFP- cell that occasionally overlay the innermost basal epidermal layer. (M–P) Single optical slice reconstructed equivalents from live whole mount-imaged 19 dpf ptch2:Kaede;runx2:mCherry and shha:GFP;ptch2:Kaede caudal fins. (M, N) ptch2:Kaede (green) is in distal runx2-marked pre-osteoblasts (magenta; white brackets) and a thin layer of tightly associated adjacent and further distally-extending basal epidermis (green brackets). (O, P) ptch2:Kaede (photoconverted; magenta) in pre-osteoblasts (magenta brackets) and co-localized with shha:GFP-expressing basal epidermis (green, white brackets). Scale bars are 250 ​μm in (A-J’) and 10 ​μm in (K–P).