Comparative biochemistry and physiology. Part B, Biochemistry & molecular biologyJul 10, 2010

Genes Responding to Low Oxygen in a Fish Species: Cloning, Expression, and Different Reactions

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Updated Apr 5, 2026

Abstract

The full-length cDNAs of HIF-1alpha and HIF-2alpha in Wuchang bream measure 3,815 bp and 3,121 bp, respectively.

HIF-1alpha encodes 774 amino acids, while HIF-2alpha encodes 835 amino acids.
Both HIF-1alpha and HIF-2alpha subunits share structural similarities in their DNA-binding and dimerization domains, but differ in the transactivation domain.
HIF-1alpha mRNA is highly expressed in the liver, gill, and testis, while HIF-2alpha mRNA is abundantly expressed across most tissues.
Both HIF-1alpha and HIF-2alpha mRNAs are present in all stages of embryogenesis with a ubiquitous expression pattern.
HIF-2alpha mRNA levels significantly increase during hypoxic treatment, up-regulated by 910% in the liver and 320% in the kidney, while HIF-1alpha levels remain unchanged.

Simplified

Transcriptional responses to hypoxia are primarily mediated by hypoxia-inducible factor (HIF) alpha subunits, i.e. HIF-1alpha, -2alpha and -3alpha. In fish, the molecular constructions, expression characteristics and hypoxic regulation of HIF-alpha subunits are still not well known. In this study, we identified the HIF-1alpha and HIF-2alpha full-length cDNAs in a hypoxia-sensitive fish species Wuchang bream, Megalobrama amblycephala. The whole length of HIF-1alpha cDNA was 3,815bp, consisting of an open reading frame (ORF) encoding 774 amino acid (aa) residues. The HIF-2alpha cDNA totaled 3,121-bp including an 835-aa ORF. The Wuchang bream HIF-1alpha and HIF-2alpha subunits were structurally similar in the DNA-binding and dimerization domains, but differed in the transactivation domain. In adult fish, both HIF-1alpha and HIF-2alpha mRNAs were detected in different tissues under normoxic conditions. HIF-1alpha mRNA was highly expressed in the liver, gill and testis, whereas HIF-2alpha mRNA was abundantly expressed in most of the Wuchang bream tissues. Both HIF-1alpha and HIF-2alpha mRNAs were detected in all stages of embryogenesis and expressed in a ubiquitous pattern. In contrast to HIF-1alpha, the mRNA levels of HIF-2alpha fluctuated in different stages, with higher expression in the zygote, 8-, 28-, 48- and 52-hr post fertilization (hpf) embryos. During hypoxic treatment, the mRNA levels of HIF-2alpha were significantly (p<0.01) up-regulated to 910% in the liver and 320% in the kidney, whereas no significant changes of HIF-1alpha mRNA were observed in the corresponding tissues. These results suggest that the Wuchang bream HIF-1alpha and -2alpha would be involved in different physiological functions under normoxia and hypoxia situations.

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Genes Responding to Low Oxygen in a Fish Species: Cloning, Expression, and Different Reactions

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