Fig. 3

Fig. 3 Expression of rasgef1b during early embryogenesis. (A) Ubiquitous distribution of maternal transcripts at 64-cell stage. (B) At dome stage, expression is restricted to dorsal marginal blastomeres. (C) At 60% epiboly stage, rasgef1b is expressed in the germring showing a gradient of expression with highest levels on the dorsal side (dorsal to the right). A cross section of the shield region (D) reveals expression in the epiblast. (E) At 70% epiboly, rasgef1b transcripts are detectable in the forerunner cells (black arrow). (F) At tailbud stage (tb), rasgef1b is expressed in axial mesoderm (black arrow) and in the presomitic mesoderm (black arrowhead). (G) At the 5-somite stage, expression is strongest in adaxial cells and forming somites. (H) At 15-somite stage, rasgef1b is expressed in the region of the diencephalon (asterisk), the MHB (black arrow) and in the hindbrain (black arrowheads). Cross section (I) shows that rasgef1b is not expressed in the notochord (nc) but in all tissues surrounding the notochord. Indicated are adaxial cells (black arrows), ventral mesendoderm (black arrowheads) and spinal cord (sc). The dorsal view (J) shows that the expression in adaxial cells is arranged in clusters (white arrow), and somitic expression is strongest in the anterior part of the somite (white arrowheads). Embryos are shown from lateral (A–C and H) or dorsal (E–G) with anterior to the left (H) or anterior to the top (F, G, and J). Scale bars: A–C and E–H, 100μm; D, I, and J, 25μm.