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Fig. 10. Hh secreted from the ventral presumptive brain, and not the axial
mesoderm, is required for condensation of crest cells on the roof of the
stomodeum and the subsequent formation of the anterior craniofacial
skeleton. (A-C) Lateral views of 30 hpf fli1:GFP embryos
co-injected with shh and twhh morpholinos (Hh MO).
(D-G) Dorsal views of Alcian stained 4 dpf neurocrania and
palatoquadrates from control transplanted embryos (D) or embryos co-injected
with Hh MO (E-G). (A,E) Co-injection of Hh MO causes failure of crest cells to
condense on the stomodeal roof (A, arrowhead) and the development of the
derivatives from this region, the anterior neurocranium and pterygoid process
(E, arrowhead; skeletal index=0.1, n=57). (B,F) Transplantation of
wild-type brain into Hh MO-injected embryos is capable of rescuing the
condensation of neural crest cells (B, arrow) and the skeletal derivatives
almost to wild-type morphology (F, arrow, skeletal index=2.2, n=40,
ANOVA F ratio=64.481, P<0.0001, Tukey-Kramer shows significance is
only attributable to wild-type brain transplant). (C,G) Transplantation of
axial mesoderm, including prechordal plate (C, inset), into Hh MO injected
embryos has no effect on crest cell condensation (C, arrowhead) or on anterior
neurocranium and upper jaw cartilage morphology (G, arrowhead, skeletal
index=0.2, n=14). Anterior is leftwards. am, axial mesoderm; br,
brain; WT, wild type. Scale bar: 50 µm.
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