CLONE AND EXPRESSING ANALYSIS OF FGFRHL-1 IN CTENOPHARYNGODON IDELLUS AND CULTER ALBURNUS

Fibroblast growth factor receptor homolog 1 (fgfrhl-1) gene is a member of the fgfr gene family currently detected only in the genomes of fish. The sequence of fgfrhl-1 is highly conserved during fish evolution, however, the distribution of fgfrhl-1 and its specific function remains unclear. In this study, we cloned the full-length cDNA of fgfrhl-1 from two distant fish species, the grass carp, Ctenopharyngodon idellus, and the Culter alburnus, and analyzed its expression in various adult tissues. The results showed that the full-length of fgfrhl-1 cDNA sequence of grass carp was 1472 bp, containing a 213 bp 5′-UTR, a 1203 bp open reading frame and a 56 bp 3′-UTR. The full-length fgfrhl-1 cDNA sequence of C. alburnus was 1886 bp, containing a 298 bp 5′-UTR, a 1203 bp open reading frame and a 385 bp 3′-UTR. The gene identified in both fish species encoded 400 amino acids, and the homology of the predicted amino acids sequences between them was 95.5%. The secondary structure prediction revealed that Fgfrhl-1 in both fish species has an intracellular tyrosine kinase domain, a transmembrane helix domain and an extracellular ligand recognizing and binding domain similar to those of FGFR, and that the extracellular domain of Fgfrhl-1 lacks three Ig-like domains that included in classical FGFRs. Semi-quantitative RT-PCR analysis explored that fgfrhl-1 was expressed in heart, gill, liver, spleen, caudal fin and intermuscular septum but not in muscle fibers in both fish species. In situ hybridization results revealed that fgfrhl-1 was expressed in connective tissues and vessels but not in the structure formed by mesenchymal cells. These results indicated the similar expression pattern of fgfrhl-1 of two different fish species mainly in the connective tissue and vessel cells of various tissues and organs, indicating that fish fgfrhl-1 may play a unique role in regulating differentiation or function maintenance of connective tissues and vessels.