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Cadmium (Cd2+) and mercury (Hg2+) are two kinds of non-essential heavy metals. Cd2+ and Hg2+ can cause thyroid disruption, but very few researchers have investigated the thyroid-disrupting effects of these metals on fish, specifically during their early developmental transition stage from embryos to larvae. In this study, wild-type zebrafish embryos were exposed to varying concentrations (contents) of Cd2+ (0, 10, 100, and 1000 μg/L) and Hg2+ (0, 0.1, 1, and 10 μg/L) for 120 h. Thereafter, the thyroid hormone contents and transcriptional changes in the genes, including thyroid stimulating hormone-β (tshβ), thyroglobulin (tg), sodium-iodide symporter (nis), thyroid peroxidase (tpo), transthyretin (ttr), thyroid hormone receptor-α and -β (thrα, thrβ), types I and II iodothyronine deiodinase (dio1, dio2), and uridine diphosphate glucuronosyltransferase 1 family a, b (ugt1ab) associated with the hypothalamic-pituitary-thyroid (HPT) axis were measured. Results showed that zebrafish embryos/larvae malformation rates were significantly higher in the Cd2+ and Hg2+ groups. A significant increase in the thyroxine (T4) concentration and a decrease in the triiodothyronine (T3) concentration were observed in the Cd2+-exposed zebrafish embryos/larvae. On the other hand, the T4 and T3 concentrations were observed to be significantly increased after Hg2+ exposure. Additionally, changes were noted in the expression patterns of the HPT axis-linked genes after Cd2+ and Hg2+ exposure. Based on the results of the principal component analysis (PCA), it was concluded that Cd2+ exposure significantly affected the thyroid endocrine system at a concentration of 100 μg/L, whereas Hg2+ exposure led to a thyroid disruption at a low concentration of 0.1 μg/L. Thus, this study demonstrated that exposure to Cd2+ and Hg2+ metal ions induced developmental toxicity and led to thyroid disruption in zebrafish embryos/larvae. [ABSTRACT FROM AUTHOR]

Whole genome transcriptomic studies are powerful for characterizing the molecular mechanisms underlying the physiological effects of chemicals, and are informative for environmental health risk assessment. Alkylating agents are an abundant class of chemicals that can damage DNA in the environment, and are used for anticancer treatments. Currently, little is known regarding the molecular mechanisms of toxic alkylating agents in zebrafish cell lines. In this study, RNA-sequencing was used to investigate the transcriptomic responses of zebrafish ZF4 cells following exposure to themodel genotoxicant methyl methanesulfonate (MMS). The half-maximal inhibitory concentration (IC50) of MMS was 639.16 ± 61.8μm, and apoptosis was induced within 24 h of exposure. RNA sequencing identified 3601 differentially expressed genes (DEGs) that were upregulated and 3037 that were downregulated. Gene ontology enrichment analysis revealed that most DEGs belonged to synthesis and metabolism categories. RNA-associated processes were the most upregulated, while cell cycle and adhesion were the most repressed processes, and neuron-related processes were the most downregulated developmental process. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis identified DNA damage repair, cell cycle, apoptosis and spliceosome as overrepresented terms. Six types of alternative splicing were detected. In total, 1156 alternative splicing DEGs were specifically expressed followingMMS treatment, many of which belonged to metabolism and catabolic process categories. Cluster analysis of orthologs was able to extrapolate toxicotranscriptomic data between zebrafish and yeast. These results provide insight into the genome-wide response of ZF4 cells following exposure to MMS, and this knowledge will inform future toxicogenomic data analysis and environmental health risk assessment. [ABSTRACT FROM AUTHOR]

We developed a new method for soluble expression of phage-displayed scFv antibody specific for zebrafish vitellogenin. The scFv antibody F5 could bind zebrafish vitellogenin specifically in phage-displayed form but not soluble form. The gene of scFv antibody F5 was cloned into vector pET 32a and transferred into Escherichia coli ori DE3. With inducible expression, soluble scFv antibody 32a-F5 was obtained successfully and could also specifically bind to zebrafish vitellogenin. The insoluble expression of phage-displayed scFv antibody was a common problem in the practical use of phage display. This study offered a feasible way to express soluble scFv antibodies with biological activity.

Various polyclonal and monoclonal antibodies have been developed for vitellogenin (Vtg) bioassays in different aquatic species. Preparation of these reagents is time-consuming and expensive. In the present study, a phage-displayed, recombinant, single-chain variable fragment (scFv) format antibody library was constructed using splenic mRNA from non-immunized mice. After 3 rounds of panning, 3 scFv antibodies with specificity for the highly conserved N-terminal region of cyprinid fish Vtg were isolated. One of these, antibody H4, bound purified Vtg from common carp Cyprinus carpio, zebrafish Danio rerio and Chinese rare minnow Gobiocypris rarus with similar affinities and detected Vtg in zebrafish plasma samples. This study provides a simple, low cost Vtg bioassay for plasma samples from a variety of cyprinid fish.