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#dorsal cells

2 public questions tagged with this topic.

amphibian Development-l

Which molecule is critical for specifying dorsal cells after fertilization?

Dorsal axis specification after fertilization depends on stabilization and nuclear localization of beta-catenin. Cortical rotation delivers Dishevelled and GBP that locally inhibit GSK-three destruction complex, preventing beta-catenin phosphorylation and proteasomal degradation. Stabilized beta-catenin enters dorsal vegetal nuclei, complexes with TCF transcription factors to activate siamois and twin homeobox genes. These transcription factors induce Spemann organizer genes goosecoid, chordin, noggin, and Xnr3 essential for dorsal mesoderm and neural induction. Neither VegT nor Sox17 nor Smad2 directly initiates dorsal determination without beta-catenin input, confirming central role.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 8: Wnt beta-catenin specifies dorsal cells organizer.

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frog development

Expression of a dominant negative GSK3 in dorsal cells results in:

Dominant-negative GSK3 expressed in dorsal marginal zone further inhibits already partially suppressed GSK3 activity dorsally, leading to even greater beta-catenin stabilization and hyperdorsal phenotype. Extra beta-catenin expands organizer gene domains chordin and goosecoid laterally, converting paraxial and lateral mesoderm into axial notochord and somitic tissue, enlarging neural plate while reducing ventral blood islands and epidermis. This contrasts ventralization seen with constitutively active GSK3. Result is dorsalized embryo with radial neuralization and exaggerated dorsal structures due to enhanced Wnt signaling. This illustrates conserved developmental logic of morphogen gradients patterning embryonic axes through Wnt and BMP antagonism.

Ref: Heasman, Wnt signaling in Xenopus patterning, Development Journal, GSK3 mutant phenotypes.

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