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#embryo patterning

2 public questions tagged with this topic.

amphibian -ll

VegT mRNA depletion results in embryos that are:

VegT is maternally encoded T-box transcription factor localized vegetally, essential for initiating Nodal transcription Xnr1,2,4,5,6 and endoderm specification via Sox17 and Mix. Antisense oligonucleotide depletion of VegT abolishes endoderm and mesoderm gene activation because Nodal signals absent, leaving animal hemisphere under unopposed BMP. Caps become entirely epidermal keratin and ciliated cells with expanded epidermis markers, producing embryo lacking gut, muscle, notochord and blood, purely epidermal ball. Rescue requires Xenopus Nodal mRNA injection demonstrating VegT master regulator of mesendoderm and epidermal repression.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 9: VegT depletion results in entirely epidermal embryos.

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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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