Hypoxia modifies the expression of clock genes in zebrafish larvae

Abstract

Hypoxia is known to stimulate a wide range of responses at the organismic and the cellular level. The hypoxia inducible factor (Hif) appears to be the master key controlling the expression of a vast number of genes in order to coordinate acclimation to hypoxic conditions. Using real time PCR hypoxia induced expression levels of various Hif isoforms and of genes downstream in the Hif signalling pathway were assessed under different levels of hypoxia. Under hypoxia the circadian expression patterns of oxygen regulated genes were modified, suggesting a connection between circadian and hypoxic signalling pathways. Subsequent analysis of the clock genes period and clock revealed a down regulation of period expression starting 17h after the onset of hypoxia. During long term hypoxia (between 9 and 15 dpf) both genes were upregulated. It is hypothesized that the modification of the expression of clock genes contributes to achieve a general metabolic down regulation under hypoxic conditions.