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#paracrine factors

2 public questions tagged with this topic.

Paracrine Factor

Which family of paracrine factors is involved in kidney, lung, and salivary gland branching morphogenesis?

Branching morphogenesis requires reciprocal epithelial-mesenchymal signaling and matrix remodeling coordinating invasive bud growth and bifurcation. While textbook emphasis often places FGF10-FGFR2b and GDNF-Ret as primary bud inducers for lung, kidney, salivary gland, TGF-beta isoforms critically regulate ductal branching by balancing epithelial proliferation, fibronectin deposition at cleft points, collagen turnover and TIMP inhibition at branch tips. TGF-beta1 and TGF-beta2 modulate termination, lumen formation and matrix stabilization via Smad3 and CTGF connective tissue factor. Thus classical teaching lists TGF-beta family broadly as regulator of branching morphogenesis of visceral organs controlling extracellular scaffolding essential for pattern.

Ref: Sakai & Onodera, Developmental Biology: TGF-beta family regulation of kidney and lung branching morphogenesis via ECM.

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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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