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#chordin

5 public questions tagged with this topic.

amphibian -ll

Which protein inhibits BMP signaling in the dorsal ectoderm?

Follistatin secreted by organizer and dorsal ectoderm binds Activin and BMPs directly in extracellular matrix, sequestering ligands from type I/II receptors, preventing Smad1/5/8 phosphorylation. In dorsal ectoderm during gastrulation, BMP antagonism by Follistatin together with Noggin and Chordin lowers phospho-Smad1 levels, permitting Sox2-positive neural plate specification instead of epidermal keratin. Knockdown of Follistatin elevates BMP, ventralizes ectoderm causing epidermal expansion. VegT and Wnt8 not BMP inhibitors, GBP regulates GSK-3 earlier. Follistatin action specific for dorsal neural induction via BMP inhibition during gastrulation.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 10: BMP antagonists - Follistatin inhibiting BMP in dorsal ectoderm.

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frog development

Ventral blastomere injection with chordin induces:

Chordin similarly binds BMPs via cysteine-rich von Willebrand domains sequestering ligands extracellularly. Ventral overexpression creates ectopic zone where BMP signaling abolished, allowing ventral marginal zone cells to adopt dorsal mesoderm fate expressing MyoD, collagen and forming notochordal tissue, while overlying ventral ectoderm neuralizes expressing NCAM. Neighboring cells recruited into secondary axis complete with somites and neural tube mirroring Spemann graft secondary axis induction. Ventralization never results from BMP antagonists. Therefore injection with chordin induces secondary axis phenocopying organizer transplantation demonstrating sufficiency. This illustrates conserved developmental logic of morphogen gradients patterning embryonic axes through Wnt and BMP antagonism.

Ref: Sasai et al., Chordin secondary axis induction in Xenopus, Cell 1994, BMP antagonist function.

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