Cold stress and light signals induce the expression of cold-inducible RNA binding protein (cirp) in the brain and eye of the Japanese treefrog (Hyla japonica)

Hibernation is an important physiological animal behavior. However, the molecular mechanism by which hibernation is regulated remains unknown. The Japanese treefrog (Hyla japonica) usually hibernates in the winter. Since this treefrog is an ectothermic animal, its hibernation is thought to be linked to the environmental temperature. In murine cells, gene expression for the cold-inducible RNA binding protein (cirp) is induced simply by cold stress. Therefore, it was hypothesized that the treefrog would also have increased expression of cirp during the hibernation season. In this report, we describe the cloning of the treefrog cirp gene and a quantitative analysis of its expression with real-time PCR. Like its homologs, treefrog cirp was found to be expressed in response to a cold stress, and its transcript was detectable in the brain, eye and ovary. Furthermore, we found that light signals could also induce the expression of cirp, and the total amount of cirp expression in both the brain and eye was significantly higher in December than in July. These results suggest that the expression of cirp in this treefrog is physiologically induced by environmental factors, such as cold stress or light signals.