While all the EGFP-injected embryos showed unaltered wild-type or shh−/− mutant patched1 expression pattern (Fig. 6A, D, "low"), over-expression of dnPKA-GFP led to ectopic spreading of patched1 expression in 87,7 +/− 3,8% of embryos (Fig. 6A, D, "high").
Suggesting regulation of Fgf8 expression by the canonical Wnt pathway, we observed strong up-regulation and caudal spreading of Fgf8 expression in the hindbrain of β-cateninstab embryos already at E8.5 (Fig. 2d,d',f, f').
Interestingly, the dorsal spreading of Phox2a expression and putative motor neuron population was seen in the midbrain but not in the rhombomere 1.
The spreading of the expression of PEPCK and GS across the entire villus is also compatible with a more differentiated phenotype of the enterocytes.
However, it is interesting to consider that this mechanism might contribute to the spreading of DUX4 expression between adjacent nuclei in a muscle fiber.
Moreover, due to the autocatalytic nature of the lac operon network, increase in the extracellular inducer concentration or slower growth led to higher average expression levels with a simultaneous spreading of the distribution of expression levels.
Despite spreading of the Shh expression, the dorsal marker Pax3, shown to be repressed by Shh [31] was only slightly down-regulated (Fig. 3i,j).
Consistent with the spreading of the Shh, expression of Gli1, a target and a mediator of Shh signalling, was enhanced in the dorsal midbrain of β-cateninstab embryos (Fig. 3g,h).
Due to the large number of patients and spread of gene expression values we quartiled each gene, giving us the following subgroups- 1 (low expression), 2 (low-medium), 3 (medium-high) and 4 (high).
Although in β-cateninstab embryos β-catenin is activated both in the midbrain and rhombomere 1, the dorsal spreading of Shh and Gli1 expression was observed only in the midbrain-like tissue.
