Overepression of Zebrafish IMP2 Induces Steatosis and ER Stress in the Liver of Transgenic Zebrafish as an Animal Model of Human Non-Alcoholic Fatty Liver Disease

Hong-Yi Gong1, Ming-Yuan Lin1, Hsiang-Po Huang2, Shao-Yang Hu1, Gen-Hwa Lin1, Wangta Liu1, Meng-Chuen Hu1, Koichi Kawakami3, Jen-Leih Wu1

1) Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan, 2) Department of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan, 3)Division of Molecular and Developmental Biology, National Institute of Genetics, Mishima, Japan

  IGF2 mRNA-binding protein 2 (IMP2/IGF2BP2) belonging to VICKZ RNA binding protein family, was also identified as an auto-antigen p62 aberrantly expressed in the human hepatocellular carcinoma (HCC). The roles of IMP2 during HCC progression, from chronic nonalcoholic fatty liver disease (NAFLD) to HCC are still poor understood. To date, no any animal model of IMP2 had been reported. We had first established IMP2overexpressed transgenic animals with ubiquitous expression and liver- specific Tet-Off expression system, respectively by using Tol2 transposonmediated transgenesis in zebrafish. Severe fatty liver was observed in the liver sections of 2.5 month F1 transgenic zebrafish with high level IMP2 overexpression by HE and Oil Red-O staining. IMP2 affected genes in liver were analyzed by using zebrafish microarray and Q-PCR. Zebrafish IGF2b and AKT were increased in liver of highly IMP2-overexpressed transgenic zebrafish. Enzymes involved in fatty acid and cholesterol synthesis were identified to be up-regulated in the liver of IMP2 transgenic zebrafish. It may result from the increase of SREBP1 expression. In addition to SREBP1, transcription factors C/EBPα, HNF4α and PPARγ involved in lipogenesis were also up-regulated. Furthermore, ER stress responsive genes such as Grp78, Hyou1, XBP1 and ATF4 were activated. Pro-apoptosis bcl2 family members, FoxO1a, FoxO3a and TNFα, NFκB, Cox involved in inflammation were also increased. It indicates the progression of NAFLD is from simple steatosis to steatohepatitis in IMP2-transgenic zebrafish. Our results suggest IMP2 overexpression will trigger hepatic steatosis via IGF2/AKT signaling to activate lipogenic transcription factors leading to synthesis of fatty acids then induce ER stress in the liver of transgenic zebrafish during the progression of NAFLD. It may provide the molecular mechanism of IMP2 in the initiation of NAFLD and HCC.