The zebrafish fgf family.

Fibroblast growth factors (FGFs) are secreted polypeptide growth factors. The FGF signaling system plays crucial roles in multiple developmental processes in vertebrates. The human FGF family comprises 22 members. Although 16 zebrafish fgfs have been reported, the zebrafish fgf family has not been well elucidated. We have identified 11 additional zebrafish fgfs by conducting a homology-based search in the zebrafish genome and cDNA databases. The zebrafish fgf family now comprises at least 27 members. By conducting phylogenetic and gene location analyses, we examined relationships of zebrafish fgf genes with human FGF genes. All the zebrafish orthologs of human FGFs except for FGF9 have been identified. Zebrafish fgf9 might have been lost from the genome during evolution. In addition, six paralogs of zebrafish fgf genes have been identified. The phylogenetic analysis suggests that the zebrafish fgf gene family can be divided into seven subfamilies. The zebrafish fgf subfamilies are essentially consistent with the human FGF subfamilies, although some include potential paralogs. As the zebrafish system has proved useful for studying gene functions and genetic diseases, the present findings will be useful for elucidation of roles of FGFs in zebrafish and humans.