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Fig. 2. Cell-to-cell variability in the source or target affects the gradient
fluctuations differently. (A) Idealized situation with fluctuating
production rate in the source (different colors), but identical target cells.
Morphogen concentration c along a slice (dashed line) in the
y-direction close to the source (bottom left), and at a larger
distance from the source (bottom right). (B) Theoretical
(x) for the situation in A based on the model in
Fig. 1C in two dimensions.
Here, j fluctuates, while D and k are constant.
(x) decreases with increasing distance x from the
source, as in A. (C) The opposite situation to A: different target
cells, identical source. (D) Calculation corresponding to C based on
the model in Fig. 1C in two
dimensions. D and k fluctuate, j is constant.
Following an abrupt decrease very close to the source,
(x)
increases with increasing x. (E)
(x) when
cell-to-cell variability affects both the source and the target, i.e. with
fluctuating j, D and k. The effects in A and C are
superimposed. A pronounced minimum of
(x) at a finite distance
from the source occurs. Whereas its location and the magnitude of
(x) depend on parameter choice, the qualitative behavior of the
curve is independent of these parameters for different noise intensities of
the same order of magnitude. Parameters in B,D,E are
D/a=7,
D/D0=1,
k/k0=1,
j/j0=0.37 (for details, see
continuum limit and Fig. S2 in the supplementary material).