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#lens induction

3 public questions tagged with this topic.

Paracrine Factor

Which family of paracrine factors plays a key role in limb development, lens induction, and segmentation?

Fibroblast Growth Factor family comprises 22 ligands signaling via four RTK FGFR1-4 requiring heparan sulfate cofactor for high-affinity binding and dimerization. During development, FGF10 from lateral plate mesoderm induces FGF8 in apical ectodermal ridge driving limb outgrowth via positive feedback loop with Sonic Hedgehog from zone of polarizing activity maintaining proliferation and patterning. FGFs from optic vesicle induce lens placode in surface ectoderm via Pax6 upregulation, and FGF8 from isthmus organizer patterns midbrain-hindbrain boundary. Segmentation clock regulated by FGF gradient opposing retinoic acid. Mutations cause skeletal dysplasias highlighting broad patterning.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 18: FGF family roles in limb bud outgrowth, lens induction, segmentation.

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Eye Lens Induction -l

Which of the following signaling pathways is involved in lens induction?

Lens induction relies heavily on fibroblast growth factor signaling for proliferation, placode maintenance and fiber differentiation. FGF1, FGF2 from neural retina and vitreous humor activate FGFR2b and FGFR3 in lens epithelium via Ras-MAPK and PI3K-Akt pathways, upregulating L-Maf, Prox1, c-Maf and crystallins. Exogenous FGF beads mimic optic vesicle inducing activity in chick explants, while dominant-negative FGFR abolishes lens vesicle invagination. Unlike Hedgehog or JAK-STAT which pattern other tissues, FGF provides sustained dosage-dependent cue that promotes lens placode thickening, survival and terminal differentiation into transparent fiber cells.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: FGF signaling pathway in lens induction and differentiation.

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Eye Lens Induction -ll

Which of the following signaling pathways is involved in lens induction?

Lens induction requires fibroblast growth factor signaling synergizing with BMP4 from optic vesicle. FGF family members FGF1, FGF8, and FGF2 activate Ras-MAPK and PI3K pathways in competent head ectoderm enhancing Sox2 and L-Maf expression and promoting placodal proliferation and crystallin synthesis. Hedgehog suppresses eye field centrally, Notch regulates differentiation timing but not primary induction, JAK-STAT influences other tissues. Experimental implantation of FGF beads near embryonic ectoderm induces ectopic lens markers, while FGFR inhibition blocks lens formation, evidencing FGF requirement in lens inductive cascade and fiber differentiation.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 12: FGF signaling in lens induction and fiber differentiation.

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