Identification of a novel fibroblast growth factor, FGF-22, preferentially expressed in the inner root sheath of the hair follicle.

We isolated cDNA encoding a novel fibroblast growth factor (FGF-22) (170 amino acids) from human placenta. Of the FGF family members, FGF-22, which appears to be a secreted protein, is most similar to FGF-10 and FGF-7 (approximately 46% and approximately 40% amino acid identities, respectively). The human FGF-22 gene was localized on chromosome 19p13.3. We also isolated mouse cDNA encoding FGF-22 (162 amino acids) from the skin. Mouse FGF-22 shows high homology (87% amino acid identity) to human FGF-22. Mouse FGF-22 mRNA was found to be preferentially expressed in the skin among the mouse adult tissues examined by Northern blotting analysis. By in situ hybridization, FGF-22 mRNA in the skin was found to be preferentially expressed in the inner root sheath of the hair follicle. Therefore, FGF-22 is expected to be a unique FGF that plays a role in hair development.