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#instructive induction

3 public questions tagged with this topic.

Morphogen Induction-l

What property distinguishes instructive induction from permissive induction?

Distinction between instructive and permissive induction lies in provision of novel fate information versus supportive environment. Instructive induction actively redirects competent cells toward new fate via specific instructive ligand altering gene regulatory network, e.g., mesenchyme instructing epithelium to form salivary branching via FGF10. Without instructive signal alternative fate does not occur. Permissive induction permits execution of already determined program by providing extracellular matrix, survival factors or hormones permitting differentiation but not changing fate choice. Therefore instructive requires specific signal to induce differentiation, permissive allows differentiation without specific instructive cue, relying on tissue autonomy plus environment permitting expression.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 3: Instructive vs Permissive Induction Differences.

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Morphogen Induction-l

Which of the following is an example of instructive induction?

Instructive induction changes fate of responding tissue by delivering novel positional cues that redirect gene regulatory network. In recombination, epithelium that would form non-specific bud differentiates into salivary gland with branched lumens when combined with salivary mesenchyme, into mammary gland with milk production when combined with mammary mesenchyme. Mesenchymal FGF10, BMP2, Wnt signals activate specific enhancers altering epithelium transcription program via Pea3, Sox9 and GATA3. Differentiation after migration or release of morphogens describes phenomena but not fate instruction. Therefore mesenchyme instructing epithelium to acquire organ-specific architecture is canonical example of instructive induction directing pattern and cytodifferentiation during organogenesis.

Ref: Wessells, Tissue Interactions in Development, Chapter 4: Epithelial-Mesenchymal Instructive Induction.

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Induction Morphogen -ll

What property distinguishes instructive induction from permissive induction?

Instructive induction provides new positional information that changes responder fate, requiring specific ligand-receptor interaction leading to altered transcription program and commitment. For example, ureteric bud-derived GDNF induces mesenchymal-to-epithelial transition and nephron gene expression via Ret receptor and Wnt4 cascade. Permissive induction does not direct fate; competent tissue already specified only needs permissive environment like extracellular matrix or trophic factor to realize intrinsic program. Blocking instructive signal abrogates fate change, while permissive signals can be replaced by unrelated substitutes supporting survival. Therefore specificity and fate-changing instruction defines instructive versus permissive mechanisms in development.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 3: Instructive versus Permissive Embryonic Induction.

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