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Comparative analysis of the tissue distribution of three fibroblast growth factor receptor mRNAs during amphibian
C Launay1, V Fromentoux, C Thery
1Groupe de Biologie Expérimentale, URA-CNRS 1135, Université Pierre et Marie Curie, Paris, France.
Abstract:
We have used in situ hybridization to survey the expression pattern of three fibroblast growth factor receptor (FGFR) mRNAs (PFR-1, PFR-3 and PFR-4, which we previously identified as the amphibian Pleurodeles waltl homologs of human FGFR-1, FGFR-3 and FGFR-4, respectively) during morphogenesis. Previous work suggests that these FGFR mRNAs exhibit a distinct pattern of expression at early developmental stages. In the present study we have tested the functional activity of these receptors and shown that both FGF-1 (acidic FGF) and FGF-2 (basic FGF), but not FGF-7 (keratinocyte growth factor), can lead to their activation, suggesting that the three cDNAs encode functional receptors. Results from in situ hybridization indicate that various FGFRs are involved in various developmental events. Their involvement in these processes is both overlapping and distinct. During the differentiation of the central nervous system (CNS), PFR-1 and PFR-4 mRNAs show high levels of redundant expression, while the sites of expression of PFR-3 mRNA correlate with regions, such as the diencephalon and the rhombencephalon, undergoing important anatomic changes. The three FGFR mRNAs are distinctly expressed in the cranial ganglia, the pigmented epithelia of retina and the otic vesicles. Most significantly, we found that they are strongly expressed at cranial and branchial mesenchymal condensation sites. PFR-3 mRNA is expressed earlier in this process than PFR-1 and PFR-4 mRNAs. Furthermore PFR-3 mRNA is detected in the mesenchyme of the limb bud, while PFR-1 and PFR-4 mRNAs are found in the primordia of the skeletal elements. In addition, PFR-1 mRNA is expressed in axial mesenchyme and PFR-4 mRNA is detected in the melanophores, xanthophores and in the pronephros. These results suggest that various FGFRs may be involved in distinct developmental events including cell proliferation and differentiation. We also discuss the functional redundancy of the FGFR system during amphibian morphogenesis.
Insights
Fibroblast growth factor receptors (FGFRs) play distinct roles in amphibian development. This study shows that three specific FGFRs are functionally active and involved in various developmental events, including CNS differentiation and mesenchymal condensation.
Area of Science:
- Developmental Biology
- Molecular Biology
- Genetics
Background:
- Fibroblast growth factor receptors (FGFRs) are crucial for embryonic development.
- Previous studies indicated distinct expression patterns for FGFR mRNAs in early amphibian development.
- The functional roles of specific FGFRs during morphogenesis require further elucidation.
Purpose of the Study:
- To investigate the expression patterns and functional activity of three amphibian fibroblast growth factor receptor (FGFR) mRNAs (PFR-1, PFR-3, PFR-4) during amphibian morphogenesis.
- To determine the involvement of these FGFRs in various developmental processes.
- To explore the functional redundancy within the FGFR system.
Main Methods:
- In situ hybridization was employed to map the expression of PFR-1, PFR-3, and PFR-4 mRNAs.
- Functional activity of the receptors was tested using FGF-1, FGF-2, and FGF-7.
- Expression patterns were analyzed during various stages of amphibian development.
Main Results:
- All three FGFRs (PFR-1, PFR-3, PFR-4) were shown to be functionally active, responding to FGF-1 and FGF-2.
- Distinct and overlapping expression patterns were observed for the three FGFR mRNAs in the central nervous system, cranial ganglia, retina, and otic vesicles.
- Strong expression of FGFRs was found at cranial and branchial mesenchymal condensation sites, with PFR-3 showing earlier expression.
- FGFRs were also detected in limb bud mesenchyme, skeletal element primordia, axial mesenchyme, and pigment cells.
Conclusions:
- The three studied FGFRs are functional and play diverse, sometimes overlapping, roles in amphibian morphogenesis.
- FGFRs are involved in key developmental events such as CNS differentiation, mesenchymal condensation, and pigment cell development.
- The findings highlight the complexity and functional redundancy of the FGFR system in regulating amphibian development.