Upregulated Hedgehog Signaling Promotes Zebrafish CNS Tumorigenesis. Danio rerio

Using a cytokeratin 5 gene promoter, we ectopically expressed a constitutively active zebrafish smoothened (smoa1) in presumably glial progenitor cells of zebrafish CNS. Stable transgenic zebrafish developed retinal tumors and low grade glioma of the optic nerve. Microarray analysis showed upregulation of Hh downstream targets of ptc1, gli1 and gli2a in tumors. Immunofluorescence studies confirmed overexpression of Pax2, GFAP, S100 and Sox2, specifically in gliomas. We also detected upregulated expression of phosphorylated pRb and Mdm2 associated with gliomagenesis. Our results suggest that dysregulated Hh signaling initiates tumorigenesis in zebrafish CNS. Zebrafish optic nerve maintains phosphorylated pRb expression, therefore provides a unique niche for pathogenesis of glioma. Overall design: RNAs from 4 gross eye tumors (from fish of 4 months of age) and 4 normal eyes from wil-type control fish were extracted and used for array analysis

我们借助细胞角蛋白5（cytokeratin 5）基因启动子，在斑马鱼中枢神经系统（central nervous system, CNS）推测的胶质祖细胞中异位表达组成型激活的斑马鱼smoothened（smoa1）。稳定转基因斑马鱼可发生视网膜肿瘤，并出现视神经低级别胶质瘤。芯片分析显示，肿瘤组织中刺猬（Hedgehog, Hh）信号通路下游靶点ptc1、gli1及gli2a的表达显著上调。免疫荧光实验证实，胶质瘤组织中特异性存在Pax2、GFAP、S100及Sox2的过表达。我们还检测到与胶质瘤发生相关的磷酸化pRb与Mdm2的表达上调。本研究结果表明，失调的Hh信号通路启动了斑马鱼中枢神经系统的肿瘤发生。斑马鱼视神经持续表达磷酸化pRb，因此为胶质瘤的发病机制提供了独特的微环境。实验设计：提取4例4月龄斑马鱼大体眼肿瘤样本及4例野生型对照斑马鱼正常眼组织的RNA，用于芯片分析。