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#competent tissue

2 public questions tagged with this topic.

Eye Lens Induction -l

Which tissue is competent to form the lens in vertebrates?

Competence for lens formation is spatially restricted. Classic transplantation by Spemann and Lewis showed head ectoderm flanking forebrain, termed preplacodal region expressing Pax6, Six1, Eya1, can form lens when apposed to optic vesicle. Trunk and limb ectoderm lacking Pax6 expression cannot be induced even with FGF8 implantation. Molecularly, only head ectoderm maintains open chromatin at lens enhancers and expresses necessary co-factors Sox2 and Otx2. Therefore lens potential is not generic ectodermal property but localized to anterior head region, ensuring lens forms adjacent to retina and not elsewhere on body surface.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Head ectoderm competence for lens formation.

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Eye Lens Induction -ll

Which tissue is competent to form the lens in vertebrates?

Only anterior head ectoderm overlying optic vesicle region possesses competence to respond to lens inductive signals and form lens. Competence is conferred by prolonged expression of Pax6, Six3, Sox2, and Otx2 while trunk and non-head ectoderm lacks these factors and fails to transcribe crystallins even when transplanted beneath optic vesicle. Any ectodermal cell is not competent, neural crest forms craniofacial mesenchyme not lens, endoderm forms gut tube. Classic transplantation of optic vesicle to trunk ectoderm yields no lens, whereas head ectoderm transplanted elsewhere can form lens, defining restricted competent territory for induction.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 12: Head ectoderm competence restricted to Pax6-positive territory.

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