Fig. 5.

Dynamic change in SHH signaling activity during limb development. (A) We detected SHH signaling activity using emerald luciferase downstream of the Gli promoter and normalized the activity relative to red luciferase activity, driven by the CMV promoter in the same limb bud. (B) Normalized luminescence activity at a posterior region for different developmental stages (open circles). Whereas signaling is at a low level only in the posterior side at stage 20, after stage 23 it is sharply increased with expansion of the activated area, which is consistent with the timing of growth mode shift from distally biased to posterior biased. SHH signaling disappears by stage 27. The blue line indicates the dynamics of volume growth rate in the posterior region.