Diel Variation in CC Chemokine Gene Expression in the Japanese Pufferfish Takifugu rubripes.

CC chemokines are key molecules in the regulation of leukocyte trafficking to the site of injury, infection, or inflammation. In recent years, some mammalian chemokines have been shown to exhibit rhythmic expression, regulated by clock genes. However, the rhythmic expression of chemokines in teleost fish remains unknown.

Circadian clock components Bmal1 and Clock1 regulate tlr9 gene expression in the Japanese medaka (Oryzias latipes).

Currently, circadian regulation of immune molecules in lower vertebrates, particularly, diurnal oscillation in the immune status of a fish, is not well understood. In this study, the diurnal oscillation of toll-like receptor (Tlr) 9, which plays a role in pathogen recognition, was investigated in the Japanese medaka fish (Oryzias latipes). We confirmed the expression of tlr9 and clock genes (bmal1 and clock1) in the central and peripheral tissues of medaka.

Circadian oscillation of TNF-α gene expression regulated by clock gene, BMAL1 and CLOCK1, in the Japanese medaka (Oryzias latipes).

To date, little information is available on the effects of circadian oscillation on immune regulation in lower vertebrates, such as teleost fish. In the present study, regulation of circadian oscillation of inflammatory cytokine TNF-α gene expression by clock gene was investigated using model fish medaka (Oryzias latipes). Firstly, structural analysis of clock genes was performed, which revealed that medaka BMAL1 and CLOCK1 conserve functionally important domains, such as basic helix-loop-helix (bHLH) and period-aryl hydrocarbon receptor nuclear translocator-single-minded (PAS), seen in their counterparts in other vertebrates.