Editorial: Therapeutic implications of circadian rhythms

Blue light restores functional circadian clocks in eyeless cave spiders

Evolution in profound darkness often leads to predictable, convergent traits, such as the loss of vision. Yet, the consequences of such repeated evolutionary experiments remain obscure, especially regarding fundamental regulatory behaviors like circadian rhythms. We studied circadian clocks of blind cave spiders and their sighted relatives. In the field, cave spiders exhibit low per expression and maintain constant activity levels. Curiously, their clocks are not permanently lost; exposure to monochromatic blue light restores both circadian gene expression and behavioral rhythms. Conversely, blocking blue light in sighted relatives induces an arrhythmic "cave phenotype." Our RNA interference experiments suggest that clock genes regulate the rhythmicity of the huddle response, establishing a link between circadian gene networks and this behavioral rhythm. We demonstrate that circadian regulation is readily toggled and may play a latent role, even in constant darkness. Overall, our study expands understanding of circadian clock variations and paves the way for future research on the maintenance of silent phenotypes.

Circadian neurogenetics and its implications in neurophysiology, behavior, and chronomedicine

The circadian rhythm affects multiple physiological processes, and disruption of the circadian system can be involved in a range of disease-related pathways. The genetic underpinnings of the circadian rhythm have been well-studied in model organisms. Significant progress has been made in understanding how clock genes affect the physiological functions of the nervous system. In addition, circadian timing is becoming a key factor in improving drug efficacy and reducing drug toxicity. The circadian biology of the target cell determines how the organ responds to the drug at a specific time of day, thus regulating pharmacodynamics. The current review brings together recent advances that have begun to unravel the molecular mechanisms of how the circadian clock affects neurophysiological and behavioral processes associated with human brain diseases. We start with a brief description of how the ubiquitous circadian rhythms are regulated at the genetic, cellular, and neural circuit levels, based on knowledge derived from extensive research on model organisms. We then summarize the latest findings from genetic studies of human brain disorders, focusing on the role of human clock gene variants in these diseases. Lastly, we discuss the impact of common dietary factors and medications on human circadian rhythms and advocate for a broader application of the concept of chronomedicine.

Computational modeling of the cell-autonomous mammalian circadian oscillator

This review summarizes various mathematical models of cell-autonomous mammalian circadian clock. We present the basics necessary for understanding of the cell-autonomous mammalian circadian oscillator, modern experimental data essential for its reconstruction and some special problems related to the validation of mathematical circadian oscillator models. This work compares existing mathematical models of circadian oscillator and the results of the computational studies of the oscillating systems. Finally, we discuss applications of the mathematical models of mammalian circadian oscillator for solving specific problems in circadian rhythm biology.