Fig. 8. Gcm1 restricts expression of genes encoding mesodermal differentiation factors. Transverse sections through the tail bud of E9.5 wild-type (A,C,E,G) and transgenic (B,D,F,H) embryos were hybridized with Gcm1 (A,B), Fgfr1 (C,D), Notch1 (E,F) and Tbx6 (G,H) ³⁵S-labeled riboprobes, and then counterstained with Hematoxylin. In the transgenic tail bud, Gcm1-expressing cells form secondary neural tube-like structures (arrowheads, B). In contrast, no expression of Gcm1 is detected in the wild-type tail bud (A). Expression levels of Fgfr1, Notch1 and Tbx6 are reduced in the secondary neural tubes of the transgenic tail buds (D,F,H). (H) The small rosettes of cells with no Tbx6 expression are those that tend to form secondary neural tubes (arrowheads). Bar: 50 µm.