The Core Circadian Component, BMAL1, is Maintained Preferentially in the Pineal Gland of Aged Killifish Brain

Abstract

Circadian rhythm controls various physiological aspects for an organism to adapt to the daily repeated changes of environments. As an organism ages, a circadian rhythm is altered, yet the underlying molecular mechanism remain largely elusive. Here, we revealed, using the short-living vertebrate model, the turquoise killifish, how organismal aging alters the major circadian clock components and their spatial distribution in the brain. Old fish showed faster dampening of the free-running rhythm in swimming behavior than young fish. The regulatory modes of circadian components were distinctive in the turquoise killifish; the protein level of BMAL but not CLOCK was highly reduced. Both BMAL1 and CLOCK proteins were detected in the whole brain of young fish but they are partially co-localized. Upon aging, BMAL1 was preferentially maintained in the pineal gland than. Thus, aging is associated with not just the reduced level but also the spatial confinement of a core circadian component in the pineal gland of the turquoise killifish brain.