Fig. 3

TOPdGFP reporter expression is Wnt-responsive and dynamic throughout development. (A) Following injection with DNA encoding Wnt1-myc, ectopic reporter expression is induced outside the endogenous domain of GFP (arrowhead). (Inset) This cell expresses both Wnt1-myc, as detected by anti-myc immunostaining (red), and GFP (green). In all following panels, red autofluorescence is shown for contrast. (B) Twelve-somite embryo. mhb, midbrain/hindbrain boundary. Box indicates region depicted at higher power in (C). (C) GFP is strongly expressed in the tail epiblast and hypoblast (arrowhead) and presomitic mesoderm (psm). (D) 24-hpf embryo. Box indicates region depicted at higher power in (E). (E) GFP is present at low levels in the brain and higher levels in the otic vesicle (ov), migrating pigment cells (arrowhead), and posterior lateral line ganglion (pllg). (F) 48-hpf embryo. Left box indicates region depicted in (G) and right box indicates region depicted in (H). (G) While expression decreases in the otic vesicle (ov), it is maintained at a high level in the posterior lateral line ganglion (pllg). (H) High-power view of the posterior spinal cord shows specific TOPdGFP expression in individual neurons. (I) 72-hpf embryo. GFP is expressed in the dorsal midbrain, lens, and cranial ganglia (arrowheads).