Local heat shock induces GFP expression in multiple tissues and at multiple stages in the hs:gfp line. GFP can be induced in eye (A), hindbrain (B), forebrain (C), and somite (D). Local heat shock is effective from at least 12 hpf (C) until 5 dpf (D). GFP is activated to a depth of at least 20 μm, as shown in A', which is resliced across the red line shown in A. A, C, D: Lateral views, anterior to right; B: dorsal view, anterior is up; A': surface up.

Local heat shock induction in three transgenic zebrafish lines. The method works reliably in hs:gfp (A,D), hs: ΔTcf-gfp (B,E), and hs:slit2-gfp (C). In hsΔTcf-gfp, GFP is present 40 &mu m from the surface, as shown in E′, a reslice of E across the red line. Lateral views, anterior to right; E′: surface up.

Local heat shock does not affect axon pathfinding in the optic tract. DiI-labeled axons from heat-shocked embryos (A,B) pathfind normally through areas of the brain expressing GFP after local heat shock, as compared to control axons without heat shock (C). Lateral views, anterior to right; B′: Surface up.