Comprehensive analysis of fibroblast growth factor receptor expression patterns during chick forelimb development

Specific interactions between fibroblast growth factors (Fgf1-22) and their tyrosine kinase receptors (FgfR1-4) activate different signalling pathways that are responsible for the biological processes in which Fgf signalling is implicated during embryonic development. In the chick, several Fgf ligands (Fgf2, 4, 8, 9, 10, 12, 13 and 18) and the four FgfRs (FgfR 1, 2, 3 and 4) have been reported to be expressed in the developing limb. The precise spatial and temporal expression of these transcripts is important to guide the limb bud to develop into a wing/leg. In this paper, we present a detailed and systematic analysis of the expression patterns of FgfR1, 2, 3 and 4 throughout chick wing development, by in situ hybridisation on whole mounts and sections. Moreover, we characterize for the first time the different isoforms of FGFR1-3 by analysing their differential expression in limb ectoderm and mesodermal tissues, using RT-PCR and in situ hybridisation on sections. Finally, isoform-specific sequences for FgfR1IIIb, FgfR1IIIc, FgfR3IIIb and FgfR3IIIc were determined and deposited in GenBank with the following accession numbers: GU053725, GU065444, GU053726, GU065445, respectively.The authors wish to thank Anja Hagemann for critical reading of themanuscript and Ramiro Magno, , Fernanda Bajanca and Tatiana Resendefor their help with the figures. We thank Dr. Guojun Sheng for the gift ofthe FgfR1-4 probes. We also acknowledge Tatiana Queirós for contribut-ing to the initiation of this project. CJS is supported by Fundação para aCiência e Tecnologia (grant n SFRH/BD/33176/2007) and RPA is fundedby a Ciência2007 Program Contract (Portuguese Government). Thiswork was supported by the Fundação para a Ciência e Tecnologia,Portugal (project PTDC/SAU-OBD/099758/2008), and by EU/FP6 - Net-work of Excellence - Cells into Organs (www.cellsintoorgans.net) and by“IBB/CBME, LA, FEDER/POCI 2010”