The interactions between fibroblast growth factors (FGF) and their receptors have important roles in mediating mesenchymal-epithelial cell interactions during embryogenesis. In particular, Fgf10 is predicted to function as a regulator of brain, lung and limb development on the basis of its spatiotemporal expression pattern in the developing embryo. To define the role of Fgf10, we generated Fgf10-deficient mice. Fgf10-/- mice died at birth due to the lack of lung development. Trachea was formed, but subsequent pulmonary branching morphogenesis was disrupted. In addition, mutant mice had complete truncation of the fore- and hindlimbs. In Fgf10-/- embryos, limb bud formation was initiated but outgrowth of the limb buds did not occur; however, formation of the clavicles was not affected. Analysis of the expression of marker genes in the mutant limb buds indicated that the apical ectodermal ridge (AER) and the zone of polarizing activity (ZPA) did not form. Thus, we show here that Fgf10 serves as an essential regulator of lung and limb formation.

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We isolated the cDNA encoding a novel member of the fibroblast growth factor (FGF) family from rat embryos by homology-based polymerase chain reaction. The FGF-related cDNA encodes a protein of 215 amino acids (ϳ24 kDa), which has a conserved ϳ120-amino acid core with ϳ30 -60% amino acid sequence identity with the FGF family. This protein with a hydrophobic amino terminus appears to be a secreted protein. The cDNA was translated in a coupled in vitro transcription-translation system. The molecular mass of the translation product was observed to be ϳ26 kDa. The expression of the FGF-related mRNA in the rat embryo and adult tissues was determined by Northern analysis and in situ hybridization. The mRNA was expressed in several discrete regions of the embryo. In adult tissues, the mRNA was preferentially expressed in the lung. The expression profile of the FGF-related mRNA was different from those of other FGF family mRNAs. As this protein is the 10th documented protein related to FGFs, we tentatively term this protein FGF-10.

Fibroblast growth factors (FGFs) are important intercellular signaling molecules in developmental processes.Here, we show that FGF10 is secreted by cultured preadipocytes and that prevention of FGF10 signaling inhibits the expression of C/EBP␤ and the subsequent differentiation of these cells. An active form of C/EBP␤ rescued differentiation of the cells in which FGF10 signaling was blocked. Development of white adipose tissue and the expression of C/EBP␤ in this tissue of FGF10 knockout mice were markedly reduced, and the ability of embryonic fibroblasts derived from FGF10 knockout mice to differentiate into adipocytes was impaired. Therefore, FGF10 plays an important role in adipogenesis, at least partly by contributing to the expression of C/EBP␤ through an autocrine/paracrine mechanism. Received February 8, 2002; revised version accepted March 1, 2002. Adipose tissue contributes to regulation of energy balance, not only by serving as a reservoir of triglycerides but also by secreting circulating factors that affect food intake or metabolism (Hwang et al. 1997;Rosen and Spiegelman 2000;Fruebis et al. 2001;Steppan et al. 2001). Mature adipocytes do not undergo cell division; the number of these cells is therefore thought to increase as a result of the proliferation of preadipocytes and their subsequent differentiation into mature adipocytes. Various factors secreted by adipocytes or preadipocytes have been identified (Hwang et al. 1997;Rosen and Spiegelman 2000;MacDougald and Mandrup 2002), some of which, such as tumor necrosis factor-␣ (Petrunschke and Hauner 1994), Pref-1 (Smas et al. 1997), and Wnt-10b (Ross et al. 2000), regulate adipogenesis by inhibiting the differentiation of these cells. Although factors that promote the proliferation or differentiation of preadipocytes have also been shown to be secreted by such cells isolated from obese humans (Lau et al. 1987) or by mature rat adipocytes (Schillabeer et al. 1989), the nature of these factors has remained unclear.The fibroblast growth factor (FGF) family comprises at least 23 proteins (Yamashita et al. 2000;Ornitz and Itoh 2001) that function in an autocrine or paracrine manner and play important roles in the development, maintenance, and repair of tissues (Goldfarb 1996;Ornitz and Itoh 2001). FGF10 was initially identified in rat embryos by homology-based polymerase chain reaction (PCR; Yamasaki et al. 1996). Disruption of the FGF10 gene resulted in complete absence of limb bud formation and severe defects in the branching morphogenesis of the lung (Min et al. 1998;Sekine et al. 1999), indicating that FGF10 is important for development of these organs. On the other hand, we have previously shown that, among the major adult tissues, transcripts of the FGF10 gene are most abundant in adipose tissue . Brown adipose tissue (BAT) and white adipose tissue (WAT) constitute the two principal types of adipose tissue and perform distinct functions (Hwang et al. 1997;Rosen and Spiegelman 2000). The expression of FGF10 is restricted to WAT. In particular, F...

We isolated the cDNA encoding a novel member of the human fibroblast growth factor (FGF) family from the lung. The cDNA encodes a protein of 208 amino acids with high sequence homology (95.6%) to rat FGF-10, indicating that the protein is human FGF-10. Human FGF-10 as well as rat FGF-10 has a hydrophobic amino terminus (ϳ40 amino acids), which may serve as a signal sequence. The apparent evolutionary relationships of human FGFs indicate that FGF-10 is closest to FGF-7. Chromosomal localization of the human FGF-10 gene was examined by in situ hybridization. The gene was found to map to the 5p12-p13 region. Human FGF-10 (amino acids 40 to 208 with a methionine residue at the amino terminus) was produced in Escherichia coli and purified from the cell lysate. Recombinant human FGF-10 (ϳ19 kDa) showed mitogenic activity for fetal rat keratinizing epidermal cells, but essentially no activity for NIH/3T3 cells, fibroblasts. The specificity of mitogenic activity of FGF-10 is similar to that of FGF-7 but distinct from that of bFGF. In structure and biological activity, FGF-10 is similar to FGF-7.

We isolated the cDNA encoding a novel member (207 amino acids) of the fibroblast growth factor (FGF) family from rat embryos. Because this protein is the 18th documented member of the FGF family, we tentatively termed it FGF-18. We have also determined mouse and human FGF-18 with high amino acid identity (99.5 and 99.0%) to rat FGF-18, respectively. Among FGF family members, FGF-18 is most similar (52.7% amino acid identity) to FGF-8 and FGF-17. FGF-18 has a typical signal sequence at its amino terminus. Recombinant rat FGF-18, which was efficiently secreted by High Five insect cells infected with recombinant baculovirus containing the cDNA, induced neurite outgrowth in PC12 cells. The expression of FGF-18 mRNA was examined in adult rat tissues and embryos by Northern blotting analysis and in situ hybridization. FGF-18 mRNA of ϳ2.7 kilobases was preferentially detected in the lung among adult rat tissues examined. In rat embryos, FGF-18 mRNA was detected in several discrete regions at embryonic days 14.5 and 19.5 but not at E10.5. The temporal and spatial patterns of FGF-18 mRNA expression in embryos are quite different from those of FGF-8 and FGF-17 mRNAs reported. The present results indicate that FGF-18 is a unique secreted signaling molecule in the adult lung and developing tissues.

In six normal beagles and 27 dogs with spontaneous focal or multifocal liver lesions, contrast-enhanced ultrasonography using Sonazoid was performed. Sonazoid is a newly developed second-generation contrast agent with the ability to be used for real-time contrast imaging along with parenchymal imaging. An appropriate protocol for the evaluation of all three phases (arterial, portal, and parenchymal) was established based on the results for normal beagles. By evaluation of the echogenicity of hepatic nodules during the arterial and parenchymal phases it was possible to differentiate malignant tumors from benign nodules with very high accuracy. In 15 of 16 dogs diagnosed as malignant tumors, nodules were clearly hypoechoic to the surrounding normal liver during the parenchymal phase. Additionally, malignant tumors had different echogenicity compared with the surrounding normal liver during the arterial phase in 14 of 15 dogs. In the portal phase, there were no characteristic findings. Contrast-enhanced ultrasonography with Sonazoid appears to improve the characterization of canine focal and multifocal hepatic lesions.

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