Figure 6

modERK-KTR reads out Fgf/Erk signaling gradient formation in real time

(A) Schematic of the zebrafish embryo illustrating the lateral region imaged in (B) relative to the dorsal organizer (see Figure 1C).

(B) Quantification of Erk activity (log₂(C/N)) in the lateral region of ubiP:modErk-KTR-Clover embryos at 20 min intervals from dome (4.3 hpf) to germ ring stage (5.6 hpf). Cells were binned based on their distance in cell tiers from the embryonic margin (0). n = 3 embryos showing the per embryo mean ± SD. Also shown is an overlay of the mean levels at each time point.

(C) Overlay of the mean Erk activity (modErk-KTR) and P-Erk levels in similarly staged embryos (5.3 hpf).

(D) Representative immunofluorescence images of embryos treated with DMSO (control) or MEKi (10 μM PD-0325901) for 10–20 min from 5.0 hpf before fixation.

(E) Quantification of P-Erk levels from (D) in cell tiers relative to the embryo margin (0) showing mean ± SD. DMSO 10 min, 5 embryos; MEKi 10 min, n = 6 embryos; DMSO 20 min, n = 4 embryos; MEKi 20 min, n = 4 embryos.

(F) Quantification of modErk-KTR read out following treatment with DMSO (control) or 10 μM PD-0325901 (MEKi). Shown is the mean of n = 3 embryos per time point.

(G) Schematic comparing the dephosphorylation rates of Erk and its targets.

Scale bars, 50 μm.

See also Figure S5.