FGFR2 Signaling is Essential for Early Liver Specification in Zebrafish

• Main Authors: Shiang-yao Shih, 施翔耀
• Other Authors: Wen-pin Wang
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/12911148758968831911

碩士 === 慈濟大學 === 分子生物及細胞生物研究所 === 95 === Mesenchymal-epithelial interactions play important roles during organogenesis. The importance of fibroblast growth factor (FGF) signals in liver organogenesis has been reported in mammals. We are interested in the role of FGF signaling in the early development of liver, especially for fgfr2. Previously we found the fgfr2 was the major receptor subtype expressed in various developmental stages during zebrafish liver development. However, its’ roles in zebrafish liver development is not clear. In order to address the issue, we knocked down the expression of fgfr2 by injecting antisense morpholino (MO) into the embryos of liver type fatty acid binding protein (L- FABP)-GFP transgenic fish. The GFP signal in the liver of fgfr2 morphants was reduced. To identify the stage specifically affected by the R2-MO, we used whole-mount in situ hybridization to detect the expression of early differentiation markers ceruloplasmin (cp) and hhex at 48 hpf and 24 hpf, respectively. Both signals were decreased in the fgfr2 morphants. To further confirm these results, we also found the reduction for the expression of Pancreas Duodenum Homeobox (pdx1) and FoxA3. So we concluded that fgfr2 affected liver development at early stage. PAS staining was normal in the fgfr2 morphants, which indicated that glycogen deposition was not impaired. We will try to differentiate the effects of alternative spliced fgfr2b and fgfr2c and identify the FGF ligands in this process. Wnt2bb has been reported to be an important factor for liver specification and the expression of liver marker, hhex, was also reduced in Wnt2bb mutant fish (prt). This result was similar to the absence of hhex in the fgfr2 morphants. So we want to analyze the relationships between the fgfr2 and Wnt signaling during liver development. We overexpressed a Wnt inhibitor, dnTCF, under the control of HSP70 promoter and found the expression of FGF downstream gene, pea3, was down-regulated in the liver forming region. Later we will use this transgenic fish to examine whether ectopic expression of FGF ligand could rescue the phenotypes. From these results, we further understand how the fgfr2 signaling controls the commitment of liver specification through interacting with Wnt signaling molecules.