Figure 3. Differential sensitivity to BMP signals alters neck patterning while maintaining body feather placode periodicity and size.

(A,B) β-catenin in situ hybridization revealing the effects of recombinant BMP12 application on feather periodicity and regional distribution in wild type skin after 48 h. (C,D) Dose effects of BMP12 on the number of feather placode rows on the spinal tract of the body. Feather primordia are visualized by β-catenin in situ hybridization. (E) SOSTDC1 expression on control and 80 ng/ml BMP12 treated skin explants. Feather placodes express SOSTDC1 at their periphery on both body and neck. Upon application of BMP12, the non-placode skin of the neck expresses a higher level of SOSTDC1 than does the body (compare signal intensity in the red boxed area to that of the blue boxed area). (F) Schematic of reaction-diffusion regulatory interactions. Adjacent numbering refers to mathematical terms in the supporting methods. C_I represents the constitutive, ubiquitous production of the Inhibitor. (G) Quantification of periodicity of Activator foci in simulated neck and body with differential sensitivities to Inhibitor. C_I increases along the x-axis. (H) Pattern outcomes from reaction-diffusion dynamics in a field with graded sensitivity to the Inhibitor. Abolition of Activator foci in the more sensitive part of the field is achieved with little effect on periodic spacing in the remainder of the field, producing a macropatttern that matches the effects of BMP12 treatment on cultured skin. Colors denote local Activator concentrations, with black representing the highest and white the lowest Activator levels. Areas with high Activator concentration represent placodes.