Time in Space: Advances in the Study of Circadian Rhythms under Microgravity

Abstract

Circadian clocks, derived from long-term evolution, are endogenous mechanisms which endow the organisms to adapt to the daily cycling environment on Earth. At the molecular level, circadian clocks are controlled by a series of clock genes and other clock associated regulators. At the tissue level, circadian systems are composed of master and peripheral clocks. Circadian clocks affect physiology, cognition and behavior of almost all organisms, which dictate their adaptability to the environment. Space environmental factors, <italic>e.g</italic>., microgravity, radiation, lighting condition and social factors, dramatically differ from those on the Earth, which may lead to impacts on circadian rhythms. Therefore, circadian clock needs to be considered in the study of space life sciences. Misalignment in circadian rhythms leads to sleep disorder and affects the skeleton-muscular system, neural system, cardio-vascular system, endocrine system, and so on, and decreases the performance of astronauts. Circadian clock will be a critical factor in future space life research and in study of astronaut health and performance.