Up-regulation of autophagy-related gene 5 (ATG5) protects dopaminergic neurons in a zebrafish model of Parkinson's disease.

Parkinson's disease (PD) is one of the most epidemic neurodegenerative diseases and is characterized by movement disorders arising from loss of midbrain dopaminergic (DA) neurons. Recently, the relationship between PD and autophagy has received considerable attention, but information about the mechanisms involved is lacking. Here, we report that autophagy-related gene 5 (ATG5) is potentially important in protecting dopaminergic neurons in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model in zebrafish. Using analyses of zebrafish swimming behavior, in situ hybridization, immunofluorescence, and expressions of genes and proteins related to PD and autophagy, we found that the ATG5 expression level was decreased and autophagy flux was blocked in this model. The ATG5 down-regulation led to the upgrade of PD-associated proteins, such as ß-synuclein, Parkin, and PINK1, aggravation of MPTP-induced PD-mimicking pathological locomotor behavior, DA neuron loss labeled by tyrosine hydroxylase (TH) or dopamine transporter (DAT), and blocked autophagy flux in the zebrafish model. ATG5 overexpression alleviated or reversed these PD pathological features, rescued DA neuron cells as indicated by elevated TH/DAT levels, and restored autophagy flux. The role of ATG5 in protecting DA neurons was confirmed by expression of the human atg5 gene in the zebrafish model. Our findings reveal that ATG5 has a role in neuroprotection, and up-regulation of ATG5 may serve as a goal in the development of drugs for PD prevention and management.

[Effect of beclin1 on vincristine-induced dopaminergic neurons injury in zebrafish].

To investigate vincristine-induced dopaminergic neurons toxicity and mechanism, and explore the molecular target to reduce the toxicity, zebrafish was chosen as a model animal, based on RT-PCR, Western blotting, whole mount in situ immunofluorescence and other technical means. The results showed that the transcription levels of tyrosine hydroxylase gene and dopamine transporter protein gene were inhibited. Furthermore, the number of dopaminergic neurons was decreased by vincristine. Autophagy was suppressed and beclin1 gene expression was inhibited in a dose-dependent manner by vincristine in larval zebrafish. Up-regulated beclin1 partly reduced vincristine-induced neurotoxicity, and down-regulated beclin1 increased toxicity. Beclin1 plays an important role in vincristine-induced dopaminergic neurons toxicity.

[Toxic effects of trimethadione on zebrafish early development].

To further understand the neural toxicity and teratogenicity of antiepileptic drugs in clinic, we established a zebrafish model for antiepileptic toxicity using trimethadione as a probe drug. The results indicated that embryonic malformation occurred under trimethadione treatment in a concentration-dependent manner. The defects included growth retardation, small head, eyes and acoustic capsule, deficient semicircular canals and otolith, and abnormal cardiovascular system. The number of hair cells in neuromast ML2 was obviously reduced in the treated larvae. Whole mount in situ hybridization indicated that the gene expression patterns of brain marker genes, such as zic1 and xb51, and autophagic gene atg5 was changed significantly. The result of RT-PCR showed that the expressions of hearing genes val and hmx2 were also changed in the trimethadione-treated embryos. All these findings suggest that brain tissue and the neural sensors for body balance and hearing are the main targets of trimethadione toxicity, and that zebrafish is able to mimic mammal responses to the teratogenicity and the neural toxicity of trimethadione in the embryonic and larva development.

Systematic cloning and analysis of autophagy-related genes from the silkworm Bombyx mori.

BACKGROUND: Through the whole life of eukaryotes, autophagy plays an important role in various biological events including development, differentiation and determination of lifespan. A full set of genes and their encoded proteins of this evolutionarily conserved pathway have been identified in many eukaryotic organisms from yeast to mammals. However, this pathway in the insect model organism, the silkworm Bombyx mori, remains poorly investigated. RESULTS: Based on the autophagy pathway in several model organisms and a series of bioinformatic analyses, we have found more than 20 autophagy-related genes from the current database of the silkworm Bombyx mori. These genes could be further classified into the signal transduction pathway and two ubiquitin-like pathways. Using the mRNA extracted from the silkgland, we cloned the full length cDNA fragments of some key genes via reverse transcription PCR and 3' rapid amplification of cDNA ends (RACE). In addition, we found that the transcription levels of two indicator genes BmATG8 and BmATG12 in the silkgland tend to be increased from 1st to 8th day of the fifth instar larvae. CONCLUSION: Bioinformatics in combination with RT-PCR enable us to remodel a preliminary pathway of autophagy in the silkworm. Amplification and cloning of most autophagy-related genes from the silkgland indicated autophagy is indeed an activated process. Furthermore, the time-course transcriptional profiles of BmATG8 and BmATG12 revealed that both genes are up-regulated along the maturation of the silkgland during the fifth instar. These findings suggest that the autophagy should play an important role in Bombyx mori silkgland.

Dual Roles of Two Isoforms of Autophagy-related Gene ATG10 in HCV-Subgenomic replicon Mediated Autophagy Flux and Innate Immunity.

Autophagy and immune response are two defense systems that human-body uses against viral infection. Previous studies documented that some viral mechanisms circumvented host immunity mechanisms and hijacked autophagy for its replication and survival. Here, we focus on interactions between autophagy mechanism and innate-immune-response in HCV-subgenomic replicon cells to find a mechanism linking the two pathways. We report distinct effects of two autophagy-related protein ATG10s on HCV-subgenomic replication. ATG10, a canonical long isoform in autophagy process, can facilitate HCV-subgenomic replicon amplification by promoting autophagosome formation and by combining with and detaining autophagosomes in cellular periphery, causing impaired autophagy flux. ATG10S, a non-canonical short isoform of ATG10 proteins, can activate expression of IL28A/B and immunity genes related to viral ds-RNA including ddx-58, tlr-3, tlr-7, irf-3 and irf-7, and promote autophagolysosome formation by directly combining and driving autophagosomes to perinuclear region where lysosomes gather, leading to lysosomal degradation of HCV-subgenomic replicon in HepG2 cells. ATG10S also can suppress infectious HCV virion replication in Huh7.5 cells. Another finding is that IL28A protein directly conjugates ATG10S and helps autophagosome docking to lysosomes. ATG10S might be a new host factor against HCV replication, and as a target for screening chemicals with new anti-virus mechanisms.

HCV IRES-mediated core expression in zebrafish.

The lack of small animal models for hepatitis C virus has impeded the discovery and development of anti-HCV drugs. HCV-IRES plays an important role in HCV gene expression, and is an attractive target for antiviral therapy. In this study, we report a zebrafish model with a biscistron expression construct that can co-transcribe GFP and HCV-core genes by human hepatic lipase promoter and zebrafish liver fatty acid binding protein enhancer. HCV core translation was designed mediated by HCV-IRES sequence and gfp was by a canonical cap-dependent mechanism. Results of fluorescence image and in situ hybridization indicate that expression of HCV core and GFP is liver-specific; RT-PCR and Western blotting show that both core and gfp expression are elevated in a time-dependent manner for both transcription and translation. It means that the HCV-IRES exerted its role in this zebrafish model. Furthermore, the liver-pathological impact associated with HCV-infection was detected by examination of gene markers and some of them were elevated, such as adiponectin receptor, heparanase, TGF-ß, PDGF-α, etc. The model was used to evaluate three clinical drugs, ribavirin, IFNα-2b and vitamin B12. The results show that vitamin B12 inhibited core expression in mRNA and protein levels in dose-dependent manner, but failed to impact gfp expression. Also VB12 down-regulated some gene transcriptions involved in fat liver, liver fibrosis and HCV-associated pathological process in the larvae. It reveals that HCV-IRES responds to vitamin B12 sensitively in the zebrafish model. Ribavirin did not disturb core expression, hinting that HCV-IRES is not a target site of ribavirin. IFNα-2b was not active, which maybe resulted from its degradation in vivo for the long time. These findings demonstrate the feasibility of the zebrafish model for screening of anti-HCV drugs targeting to HCV-IRES. The zebrafish system provides a novel evidence of using zebrafish as a HCV model organism.