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Figure 2. Inhibition of Endogenous Chordin Results in Reduction of Neuroectodermal and Expansion of Ventral Mesodermal Markers A mixture of the two Chordin morpholinos (4 ng of each) was injected four times, radially, at the two-cell stage. (A and B) Expression of the organizer marker genes chordin and noggin was unchanged in wild-type (wt, left) and Chd-MO(1 2)-injected (right) embryos at early gastrula. (C) The neural plate was reduced in Chd-MO(1 2)-injected embryos, as shown by the neural marker Sox2 (stage 12). (D, E, and F) At stage 12 the expression of chordin, noggin, and follistatin was not significantly affected by Chd-MO(1 2) injection. The expression domains are shorter, indicating a mild inhibition of convergence-extension gastrulation movements. (G) RT-PCR analysis of sibling embryos. The mRNA levels of chordin, noggin, and follistatin were not significantly changed in Chd-MO(1 2)- injected embryos at stage 10.5 or stage 12. (H) At tadpole stages the A-P pattern of neural organization was relatively normal, as shown by expression of Otx2 (forebrain), Krox-20 (hindbrain), and HoxB9 (spinal cord). (I) Ventral mesoderm, marked by the expression of sizzled, is expanded in Chd-MO(1 2)-injected embryos. The upper panel shows a lateral view, and the lower panel shows a ventral view, of the same embryos. (J and K) At late tadpole stages (stage 42) Chd-MO(1 2)-injected embryos develop with smaller head structures. Histological sections (J , J′, K , and K′) revealed a reduction of midbrain (mb), pharynx (ph), eye (ey), and spinal cord (sc) and an expansion of ventral blood islands (bl) in Ch-MO(1 2)-injected embryos. No obvious changes in somites (so) or notochord (no) were observed. |
