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Updated: Aug 3, 2026
11:48
Grafting of Beads into Developing Chicken Embryo Limbs to Identify Signal Transduction Pathways Affecting Gene Expression
Published on: January 17, 2016
FGF and genes encoding transcription factors in early limb specification
1Department of Anatomy and Developmental Biology, University College London, UK. a.j.isaac@dundee.ac.uk
Mechanisms of Development
|April 27, 2000
Summary
Sonic hedgehog (Shh) and Twist (Twi) are early limb development markers. FGF signaling rapidly induces Shh and Tbx gene expression, but Fgf10 and Twi activation occurs later, suggesting distinct regulatory pathways.
Area of Science:
- Developmental Biology
- Molecular Biology
- Chick Embryology
Background:
- Sonic hedgehog (SnR), twist, and Fgf10 are key genes in early chick embryo limb development.
- Fibroblast Growth Factor (FGF) signaling plays a crucial role in initiating limb formation.
- Understanding the temporal and spatial gene expression dynamics is vital for deciphering limb development pathways.
Purpose of the Study:
- To investigate the role of FGF signaling in limb development by analyzing the expression patterns of SnR, Fgf10, twist, Tbx-4, and Tbx-5.
- To determine the temporal sequence of gene activation following FGF stimulation in chick embryos.
- To elucidate the distinct molecular pathways involved in the induction of early limb development genes.
Main Methods:
- Implantation of FGF-2/FGF-8 coated beads into chick embryo flanks to induce ectopic limb development.
- Analysis of gene expression patterns (SnR, Fgf10, twist, Tbx-4, Tbx-5) using techniques like in situ hybridization (implied).
- Comparative analysis of gene activation timing and response to different FGF stimuli.
Main Results:
- FGF-2/FGF-8 bead implantation rapidly induced ectopic limb formation and irreversible SnR activation within 1 hour.
- Ectopic Fgf10 and twist expression were activated significantly later, at 17 and 20 hours, respectively.
- FGF-10 also induced SnR, but with delayed co-activation of twist and Fgf10 via the Fgf8-expressing ridge.
- FGF-2 rapidly induced ectopic Tbx-4 and Tbx-5 expression, similar to SnR, but with distinct spatial patterns.
- The findings suggest that SnR and Tbx gene induction occur through different signaling pathways.
Conclusions:
- FGF signaling initiates limb development through rapid induction of key genes like SnR and Tbx.
- Distinct temporal activation patterns for Fgf10 and twist suggest a hierarchical or parallel regulatory mechanism.
- The differential induction pathways for SnR and Tbx genes highlight the complexity of limb patterning.
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