Examples of this behavior include sharp gene expression boundaries and the generation of traveling waves of mRNA expression from single 'trigger' patterns.
The loss of one Sharp gene resulted in a broadened τ distribution indicating an elevated variability in pacemaker regulation while in the double mutants τ was consistently shifted towards higher values (Figure 1E).
However, when Sharp gene dosage was further lowered, we observed a significant lengthening of τ (up to 0.5 h) in mice with only one or no functional Sharp allele left (Figure 1D,E and Figure S2) indicating a high degree of functional redundancy between both genes.
In this system, the behavior near half maximal expression is biologically most relevant, since it is at this very concentration that the system has to 'decide' where to draw a fairly sharp gene expression boundary as one of the first steps in constructing a spatial pattern.
Despite the discontinuity arising from the sharp gene expression domain boundaries, we proved the existence of unique, positive solutions for the partial differential equation system.
The analysis reveals how the cross-regulatory network is able to establish sharp gene expression boundaries (among target genes that, if expressed in isolation, would have a graded or uniform expression profile).
Sharp gene expression boundaries combined with gradients of gene expression within the expression domains are responsible for the (A BCE-like florA BCE-likedentity in the wild type, regular, floralhorgan kidentity flower.
Expression of miRNAs that degrade their target mRNAs shows negative correlation with the respective target mRNAs; they are expressed in adjacent spatial domains and the role of miRNAs is to clear cells of their target gene activities [ 64] and to maintain sharp gene expression boundaries.
In Central Africa, the contrast is less sharp: gene pools Is and In were found in evergreen forests with very high annual rainfall (1620 to 3480 mm; mean = 2460 mm), while SC occurred in the drier semi-evergreen forests (annual rainfall 1370 to 2050 mm; mean = 1640 mm), and SW in the forest-savanna mosaic of northern Cameroon (annual rainfall 1530 to 2090 mm; mean = 1710 mm).
The other categories shown in Figure 3 remain relatively constant during pregnancy, with a sharp increase (genes for fatty acid and cholesterol synthesis) or decrease (genes for fatty acid degradation and the proteasome) at secretory activation.
