Expression of bone morphogenetic protein-4 (BMP-4), bone morphogenetic protein-7 (BMP-7), fibroblast growth factor-8 (FGF-8) and sonic hedgehog (SHH) during branchial arch development in the chick
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1Department of Cell Biology, Vanderbilt University Medical School, Nashville, TN 37232, USA.
Insights
This study maps the expression of key signaling molecules, including Fibroblast Growth Factor 8 (Fgf-8) and Bone Morphogenetic Proteins (Bmp-4, Bmp-7), during chick embryo branchial arch development. Findings reveal specific expression patterns crucial for understanding craniofacial development.
Area of Science:
- Developmental Biology
- Molecular Biology
- Embryology
Background:
- Branchial arches are critical embryonic structures that give rise to diverse craniofacial features.
- Understanding the molecular mechanisms governing branchial arch development is essential for identifying causes of congenital abnormalities.
Purpose of the Study:
- To investigate the spatial and temporal expression patterns of Fgf-8, Bmp-4, Bmp-7, and Sonic hedgehog (Shh) signaling molecules.
- To elucidate the role of these signaling pathways in the development of chick embryo branchial arches.
Main Methods:
- In situ hybridization was employed to detect the expression of specific gene transcripts.
- Analysis was performed across various developmental stages of the chick embryo.
Main Results:
- Fgf-8 expression showed dynamic changes, becoming restricted to the posterior ectodermal margin (PEM) of the 2nd branchial arch.
- Bmp-7 was detected in branchial clefts and arches, including the PEM, while Bmp-4 localized to distal arch tips.
- Shh expression overlapped with Bmp-7 and Fgf-8 in the PEM of the 2nd arch, suggesting coordinated signaling.
Conclusions:
- The distinct expression patterns of Fgf-8, Bmp-4, Bmp-7, and Shh suggest their coordinated roles in regulating chick branchial arch morphogenesis.
- A model is proposed for the involvement of these signaling molecules in guiding branchial arch development and patterning.
Abstract:
Expression of Fgf-8, Bmp-4, Bmp-7, and shh in the branchial arches of the chick embryo is examined by in situ hybridization. Fgf-8 expression is initially broad and diffuse, becoming more tightly restricted, particularly in the epithelium of the posterior ectodermal margin (PEM) of the 2nd branchial arch. Bmp-7 transcripts, first seen at stage 12 in discrete regions corresponding to the developing branchial clefts, are later detected in both clefts and arches, including the PEM of the 2nd arch while Bmp-4 transcripts are detected at stage 18 in the distal tips of the arches. Shh expression remains localized, overlapping with both Bmp-7 and Fgf-8 in the PEM of the 2nd arch at stages 16 and 18. Based on these data, a model is proposed for the role of these signalling molecules in branchial arch development.