FGFRL1 is a neglected putative actor of the FGF signalling pathway present in all major metazoan phyla.
BACKGROUND
Fibroblast Growth Factors (FGF) and their receptors are well known for having major implications in cell signalling controlling embryonic development. Recently, a gene coding for a protein closely related to FGFRs (Fibroblast Growth Factor Receptors) called FGFR5 or FGFR-like 1 (FGFRL1), has been described in vertebrates. An orthologous gene was also found in the cephalochordate amphioxus, but no orthologous genes were found by the authors in other non-vertebrate species, even if a FGFRL1 gene was identified in the sea urchin genome, as well as a closely related gene, named nou-darake, in the planarian Dugesia japonica. These intriguing data of a deuterostome-specific gene that might be implicated in FGF signalling prompted us to search for putative FGFRL1 orthologues in the completely sequenced genomes of metazoans.


RESULTS
We found FGFRL1 genes in the cnidarian Nematostella vectensis as well as in many bilaterian species. Our analysis also shows that FGFRL1 orthologous genes are linked in the genome with other members of the FGF signalling pathway from cnidarians to bilaterians (distance < 10 Mb). To better understand the implication of FGFRL1 genes in chordate embryonic development, we have analyzed expression patterns of the amphioxus and the mouse genes by whole mount in situ hybridization. We show that some homologous expression territories can be defined, and we propose that FGFRL1 and FGF8/17/18 were already co-expressed in the pharyngeal endoderm in the ancestor of chordates.


CONCLUSIONS
Our work sheds light on the existence of a putative FGF signalling pathway actor present in the ancestor of probably all metazoans, the function of which has received little attention until now.
Bertrand
Stephanie
S
Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, edifici annex, 1a planta, 08028 Barcelona, España. stephanie.bertrand@obs-banyuls.fr
Somorjai
Ildiko
I
Garcia-Fernandez
Jordi
J
Lamonerie
Thomas
T
Escriva
Hector
H
D000818:Animals; D002816:Chordata, Nonvertebrate / Q000235:genetics*; D003063:Cnidaria / Q000235:genetics*; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D008040:Genetic Linkage; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny; D051500:Receptor, Fibroblast Growth Factor, Type 5 / Q000235:genetics*
C496379:Fgfrl1 protein, mouse; D051500:Receptor, Fibroblast Growth Factor, Type 5