Figure 1

BMP Signaling Gradients in the Pectoral Fin

(A–C) Fin of double transgenic BRE:GFP (green) and Histone2b-mCherry (red), at 60 hpf. The BRE reporter expresses GFP under the control of Smad1/5/8 enhancers from the mouse Id1 promoter (Collery and Link, 2011, Laux et al., 2011). Dashed line, fin boundaries. Anterior, left; distal, down.

(B) Region of interest (ROI, blue; with ROI midline) where gradients are deployed: endoskeletal disc, abutting the fin fold. Cartoon indicates fin axes and endoskeletal disc (ed).

(D) BRE:GFP gradient along the straightened ROI (blue; anterior left) from (B). Orange lines indicate position s=0, corresponding to intensity maxima. Length L (black line), distance between each peak signal and the ROI midpoint (dashed line).

Scale bars: 50 μm (A–C), 20 μm (D).

(E) BRE:GFP intensity profile along the ROI midline from (B)–(D), at 60 hpf. Arrowheads, intensity maxima. Intensity corresponds to signal average orthogonal to midline.

(F and G) Anterior (F) and posterior (G) intensity profiles from (E) versus position s, with respective decay lengths (λ, slope), ± SEM. Here s=0, position of peak signal as indicated in (D)–(E). Note that the gradient profile corresponds to different levels of signaling per cell and the observed gradient is not due to different cell density or different number of signaling cells (see Figures S2K–S2M). Also, the gradient does not reflect different durations of signaling or long perdurance of GFP in the BRE reporter, since Phospho-Smad1/5/9 immunostainings show similar graded distributions (Figures S1J–S1L). Black lines, exponential fits with respective goodness of fit (R²). BRE:GFP transgene used: BRE:eGFP (Laux et al., 2011).

See also Figures S1 and S2.