Figure 1.

Scheme of signaling gradient system in the presomitic mesoderm (PSM) of mouse embryos. If not stated otherwise, illustrations reflect mRNA expression patterns in the PSM of mouse embryos. Additional sites of expression (e.g., somites, neural tube) are not shown. For Akt and Erk, the distribution of the activated, phosphorylated protein is shown (p-Akt, p-Erk). For Erk, these data derive from chicken (c) and zebrafish (z) embryos. For Axin2, Dusp6, and Dusp4, the graded expression is periodically down-regulated in the posterior PSM, as indicated by the oscillation symbol (∼).