Fig. S13

Hedgehog/Smoothened signaling directs osteoblasts to laterally migrate in concert with transiently split domains of shha:GFP-expressing basal epidermis. Representative transverse sections from control and BMS-833923-treated shha:GFP fins at 96 hpa immunostained for Runx2 (red) and GFP (white) and developed using click chemistry to visualize EdU (green) incorporating cells. The sections shown represent distinct rays from two DMSO and three BMS-833923-treated fish. (A-E) Sections from the extreme distal region of the regenerating fin, beyond the location of self-renewing pObs. Stable GFP protein persists in previously shha-expressing basal epidermal cells, which now populate a single contiguous domain on each side of the fin. (F-J) Sections from the region where shha:GFP-expressing epidermis transiently split into two domains on both sides of the fin. (K-O) Proximal sections from the distal regenerate where basal epidermal cells initiate shha:GFP-expression but have not yet split into two pools. Yellow arrows point to Runx2⁺/EdU⁺ cells located more than 1 cell layer from shha:GFP-expressing epidermis. Red arrows indicate Runx2⁺ pObs located more than 2 cell layers distant from shha:GFP-positive epidermal cells. The magenta brackets denote Runx2⁺ pObs spanning the junction between split shha:GFP domains in sections from BMS-833923- treated fish. Scale bars: 50 μm.