Phylogenetic Background of Hibernation and Hibernation-Specific Proteins in Sciuridae
In mammals, hibernation is expressed in only a limited number of species, and the molecular mechanisms underlying hibernation are not well understood. We have previously demonstrated a decrease in hibernation-specific protein (HP) in the blood of chipmunks during hibernation. Recently, we revealed that HP was regulated by an endogenous circannual rhythm and conveys a signal to the brain essential for hibernation control. In most mammalian hibernators other than some squirrel species, however, the relationship between HP and hibernation remains unknown. Here, we describe the phylogenetic relationships between HP and hibernation in Sciuridae. The expression of HP gene was observed only in hibernating species. Non-hibernating species did not express HP gene even though they possessed the HP-20, -25, and -27 genes. The hibernation-associated HP cycle found in the chipmunk also occurred in other hibernating species. The phylogenetic tree in Sciuridae demonstrated that hibernating species expressing HP like ground squirrel and chipmunk, which belong to Marmotini, diverged recently from non-hibernating species not expressing HP, such as Funambulini and Protoxerini. Thus, HP is closely related to the evolution of hibernation in Sciuridae.
KeywordsGround Squirrel Fuji Photo Film Circannual Rhythm Tree Squirrel Mammalian Hibernator
We are grateful to Norikazu Hara, Hiroki Nagase, Sayuri Maruyama, Haruka Maruyama, Taeko Ishima for their excellent technical assistance and useful suggestions throughout this study.
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