Figure 6
From: Digit patterning during limb development as a result of the BMP-receptor interaction
The impact of protein production rates on digit numbers.
(A–D) The impact of changes in the FGF production rate on patterning. (A) A 91% reduction in the FGF expression rate results in the loss of one pattern (digit). (B) Additional spots emerge as the FGF production rate is increased uniformly by 50%. (C) One additional spot emerges on the posterior site (RHS) if FGF expression is enhanced by 50% only on the posterior site (RHS). Spots on the anterior side (LHS) merge as characteristic for syndactyly. (D) The number of digits at different relative FGF production rates (1 corresponds to the reference rate in Table 1) for τ = 750. Loss of digits at higher FGF production rates is due to presence of stripes; spots can be recovered if simulations are run longer. (E–H) The impact of changes in the BMP production rate. (E) Digits are lost when the BMP production rate is reduced to 50%. (F) Additional spots emerge as the BMP production rate is increased by 30%. (G) The pattern merge (polysyndactily) as the BMP production rate is increased by 50%. (H) The number of digits at different relative BMP production rates (1 corresponds to the reference rate in Table 1) for τ = 750. Note that at higher production rates pattern merge and digits are no longer observed. The constant but spatially modulated BMP production rates ρB1, ρB2 (black and blue lines) and the FGF-dependent BMP production rate ρB* (red line) have different effects on the patterning. The spatially modulated BMP ρB2 in the stalk has little impact at larger values because most BMP then binds to receptors in the stalk. The spot(s) at the proximal end of the stalk and the two spots appearing at the transition from the stalk to the circular domain were preserved under all conditions and thus not counted.
