Zebrafish developmental biology, zebrafish models for liver cancers, fish toxicogenomics and biomonitoring.
Zebrafish models for liver cancers
The zebrafish has become an increasingly popular animal model for high-throughput and low cost studies. Previously, by microarray-based transcriptome analyses, we have demonstrated that the carcinogen-induced zebrafish liver tumors share remarkable similarity with human liver tumors in cancer molecular hall markers, molecular pathways, as well as features in tumor progression, thus validating the zebrafish model for human disease. To generate reproducible zebrafish models for liver cancers, we employed a transgenic approach to over-express selected oncogenes under a liver-specific promoter. So far, we have generated a few inducible and non-inducible transgenic lines by expression of kras, myc or Xmrk; all of them are capable of producing liver cancers when they are highly expressed. In the relatively well studied kras transgenic lines, in which a constitutively active form of kras mutant (G12V) is expressed, abnormal over-growth of liver could be observed within one week of fertilization and the lesion of liver become increasingly severe with time, from hyperplasia to adenoma and to carcinoma. These tumors could be transplanted to other adult fish and survived, propagated and migrated in the host fish. We have applied two inducible transgenic systems using the Tet-on and mifepristone induction. In both inducible systems, we demonstrated that production of liver tumors could be induced at any developmental stages and even in adult fish. More interestingly, the induced tumors show rapid regression upon removal of the inducer. To explore the potential of the transgenic tumor model for future anti-cancer drug screening, we developed a protocol of using transgenic fry for liver tumor assay and found the inhibition of liver hyperplasia by several chemical inhibitors. These observations provide a basis for high-throughput chemical screening for anti-cancer drugs using our transgenic zebrafish models. Currently we are also developing rapid assays in the zebrafish model for testing potential oncogenes and tumor suppressor genes that are capable of driving hepatocarcinogenesis.
Fish toxicogenomics and biomonitoring
We are interested in use of both the zebrafish and medaka to develop tools for monitoring environmental pollution. Previously we have developed several GFP transgenic medaka lines using different inducible promoters and these transgenic medaka show inducible GFP expression in response specifically to several classes of environmental contaminants including estrogenic compounds, polycyclic aromatic hydrocarbons and heavy metals. Thus, these transgenic fish may be used for developing an online water monitoring system. Now with the advent of powerful genomic tools including DNA microarray and next generation sequencing, it is feasible to analyse transcriptome of zebrafish under different chemical insult conditions. We hypothesize that each chemical pollutant would cause some characteristic changes in transcriptomes in exposed fish and these changes may be used to predict the classes of environmental pollutants. To test the hypothesis, we exposed the adult zebrafish with more than a dozen of environment-relevant chemicals and transcriptomic data were generated by DNA microarray. We found that indeed chemical-induced transcriptomic changes could be correctly grouped based on the hierarchical clustering of transcriptomic data. However, for a robust and practical prediction of the presence of certain chemicals, it was necessary to use a small group of selected responsive genes as biomarkers for each chemical. Currently we have generated RNA-seq data from zebrafish exposed to several important environmental chemicals and preliminary bioinformatic analyses indicate that each of these chemicals up-regulates a very distinct set of genes with little overlapping. These up-regulated genes from each of the chemical treatment groups are apparently associated with different biological pathways. These observations provide a basis for identification of specific biomarker genes to be used for determine environmental contaminations through biological effects. Our long-term goal is to develop practical PCR arrays using biomarker genes identified from laboratory zebrafish and to apply universally to all wild fish species. Because of the high content transcriptomic information from these microarray and RNA-seq data, we will also analyze molecular mechanism of toxicity of each pollutant, which is valuable for risk assessment of each pollutant relevant to human health.
Li Z., Huang X, Zhan H, Zeng Z, Li C, Spitsbergen JM, Meierjohann S, Schartl M, Gong Z (2012) Inducible and repressable oncogene-addicted hepatocellular carcinoma in Tet-on xmrk transgenic zebrafish. J Hepatol. 56:419-425.
Nguyen AT, Emelyanov A, Koh CHV, Spitsbergen JM, Pairnov S, Gong Z (2012) An inducible krasV12 transgenic zebrafish model for liver tumorigenesis and chemical drug screening. Dis Model Mech. 5(1):63-72.
Huang X, Zhou L, Gong Z. (2012) Liver tumor models in transgenic zebrafish: an alternative in vivo approach to study hepatocarcinogenes. Future Oncol. 8(1):21-8.
Nguyen AT, Emelyanov A, Koh CHV, Spitsbergen JM, Lam SH, Mathavan S, Pairnov S, Gong Z (2011) High Level of Liver-specific Expression of Oncogenic KrasV12 Drives Robust Liver Tumorigenesis in Transgenic Zebrafish. Disease Models Mech. 4(6):801-13.
Huang X, Nguyen AT, Li Z, Emelyanov A, Parinov S. and Gong Z. (2011) One Step Forward: the Use of Transgenic Zebrafish Tumor Model in Drug Screens. Birth Defects Research Part C: Embryo Today. 93:173-181.
Lam, S.H., M.M. Hlaing, C. Yan, C.Y. Ung, S. Mathavan, Z. Duan, L. Zhu, C.N. Ong and Z. Gong (2011) Zebrafish toxicogenomical and phenotypic analyses reveal molecular insights into bisphenol-A early-life exposure toxicity. PLoS One. 6(12):e28273.
Ung CY, Lam SH, Zhang X, Li H, Ma J, Zhang L, Li B, Gong Z (2011) Existence of inverted profile in chemically responsive molecular pathways in the zebrafish liver. PLoS One. 6(11):e27819.
Ng GHB and Gong Z (2011) Maize Ac/Ds transposon system leads to highly efficient germline transmission of transgenes in medaka (Oryzias latipes). Biochimie. 93(10):1858-1864.
Korzh S, Winata CL, Zheng W, Yang S, Yin A, Ingham P, Korzh V, Gong Z. (2011) The interaction of epithelial Ihha and mesenchymal Fgf10 in zebrafish esophageal and swimbladder development. Dev Biol. 359(2):262-76.
Zheng W, Wang Z, Collins JE, Andrews RM, Steple D, Gong Z. (2011) Comparative Transcriptome Analyses Indicate Molecular Homology of Zebrafish Swimbladder and Mammalian Lung. PLoS One. 2011;6(8):e24019.
Yin A, Korzh S, Winata CL, Korzh V, Gong Z (2011) Wnt signaling is required for early development of zebrafish swimbladder. PLoS One. 6(3):e18431
Gong, Z., C.H.V. Koh, A.T. Nguyen, H. Zhan, Z. Li, S.H. Lam, J.M. Spitsbergen, A. Emelyanov and S. Parinov (2010) The zebrafish model for liver carcinogenesis. In: Molecular Genetics of Liver Neoplasia. Eds. X.W. Wang, J. Grisham and S.S. Thorgeirsson. Springer. PP.197-218.
Ung CY, Lam SH, Hlaing MM, Winata CL, Korzh S, Mathavan S, Gong Z. (2010) Mercury-induced hepatotoxicity in zebrafish: in vivo mechanistic insights from transcriptome analysis, phenotype anchoring and targeted gene expression validation. BMC Genomics 11(1):212.
Wang Z, Du J, Lam SH, Mathavan S, Matsudaira P, Gong Z. (2010) Morphological and molecular evidence for functional organization along the rostrocaudal axis of the adult zebrafish intestine. BMC Genomics 11:392.
Wang Z, Matsudaira P and Gong Z (2010) STORM: A General Model to Determine the Number and Adaptive Changes of Epithelial Stem Cells in Teleost, Murine and Human Intestinal Tracts. PLoS ONE 5(11):e14063.
Winata CL, Korzh S, Kondrychyn I, Zheng W, Korzh V, Gong Z. (2009) Development of zebrafish swimbladder: The requirement of Hedgehog signaling in specification and organization of the three tissue layers. Dev. Biol. 331:222-236.
Lam, SH, Mathavan S, Tong Y, Li H, Karuturi RKM, Wu YL, Vega VB, Liu ET and Gong Z. (2008) Zebrafish Whole-Adult-Organism Chemogenomics for Large-Scale Predictive and Discovery Chemical Biology. PLOS Genetics. 4:e1000121
Lam, S.H, Y.L. Wu, V.B. Vega, L.D. Miller, J. Spitsbergen, Y. Tong, H. Zhan, K. R. Govind a rajan, S. Lee, S. Mathavan, D.R. Buhler, E.T. Liu, and Z. Gong (2006) Conservation of gene expression signatures between zebrafish and human liver tumors and tumor progression. Nature Biotechnology 24: 73-75.
Lam, S.H. and Z. Gong (2006) Modelling Liver Cancer Using Zebrafish: A Comparative Oncogenomics Approach. Cell Cycle 5:573-577.
Lam, S.H., C.L. Winata, Y. Tong, S. Korzh, W.S. Lim, V. Korzh, J. Spitisbergan, S. Mathavan, L.D. Miller, E.T. Liu and Z. Gong (2006) Trancriptome Kinetics of Arsenic-induced Adaptive Response in Zebrafish Liver. Physilogical Genomics. 27:351-361.