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| | A Raf/MEK/ERK signaling pathway is required for development of the sea urchin embryo micromere lineage through ... |
 | | (A) Sixty-cell stage, (F) early blastula, (B,C) prehatching blastula, (G,H) hatching blastula, (I,J) early mesenchyme blastula, (D,K) mesenchyme blastula, (L,M) early gastrula (arrows in M indicate staining in the ectoderm adjacent to the PMC clusters) and (E,N,O) late gastrula. |
 | | ERK activity is required first between the prehatching blastula stage and the swimming blastula stage for ingression of the PMCs (green), and then during gastrulation for differentiation of the PMCs into spicules (yellow). |
 | | At the blastula stage, activation of the Raf/MEK/ERK signaling pathway by an unknown factor Y, allows phosphorylation of Ets1, which is crucially required for the maintenance of alx1 and Delta expression in the micromeres, and for the initiation of skeT/Tbr and other downstream genes in this lineage. |
| dev.biologists.org /cgi/content/full/131/5/1075 (7541 words) |
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