Molecular, functional, and gene expression analysis of zebrafish hypoxia-inducible factor-3α

Zhang P, Lu L, Yao Q, Li Y, Zhou J, Liu Y, Duan C. Molecular, functional, and gene expression analysis of zebrafish hypoxia-inducible factor-3 alpha. Am J Physiol Regul Integr Comp Physiol 303: R1165-R1174, 2012. First published October 3, 2012; doi:10.1152/ajpregu.00340.2012.-Hypoxia-inducible factors 1-3 (HIF1-3) are transcription factors that regulate gene expression in response to hypoxia. Compared with our extensive understanding of HIF-1 and HIF-2, our knowledge of HIF-3 is limited. In this study, we characterized the zebrafish hif-3 alpha gene and determined its temporal and spatial expression, physiological regulation, and biological activity. We show that the chromosomal location, gene structure, and protein structure of zebrafish hif-3 alpha are similar to its mammalian orthologs. When tagged with enhanced green fluorescent protein and transfected into cultured cells, zebrafish Hif-3 alpha was localized in the nucleus and stimulated reporter gene expression in a hypoxia response element-dependent manner. During early development, hif-3 alpha mRNA was detected in all tissues with higher levels in the head. This expression pattern became more apparent in larvae at the 72, 96, and 120 hours post fertilization stages. In the adult stage, hif-3 alpha mRNA was detected in all examined tissues with the highest levels in the ovary. Hypoxia treatment increased Hif-3 alpha protein levels in both embryos and adults. Hypoxia also increased hif-3 alpha mRNA expression levels, and this regulation was tissue-specific. Expression of a stabilized form of Hif-1 alpha in zebrafish embryos increased the expression of igfbp-1a, a Hif-1 target gene, whereas it did not change hif-3 alpha mRNA levels, suggesting that hif-3 alpha is not a Hif-1 alpha target. These results provide new information about the structural and functional conservation, spatial and temporal expression, and physiological regulation of hif-3 alpha in a teleost model organism.