bims-ciryme Biomed News
on Circadian rhythms and metabolism
Issue of 2024–12–22
two papers selected by
Gabriela Da Silva Xavier, University of Birmingham
  1. Analytic solutions for the circadian oscillator characterize cycle dynamics and its robustness.
  2. A Compensated Clock: Temperature and Nutritional Compensation Mechanisms Across Circadian Systems.
  1. J Math Biol. 2024 Dec 14. 90(1): 5
    Analytic solutions for the circadian oscillator characterize cycle dynamics and its robustness.
    Odile Burckard, Madalena Chaves.
      Circadian clocks form a fundamental mechanism that promotes the correct behavior of many cellular and molecular processes by synchronizing them on a 24 h period. However, the circadian cycles remain difficult to describe mathematically. To overcome this problem, we first propose a segmentation of the circadian cycle into eight stages based on the levels of expression of the core clock components CLOCK:BMAL1, REV-ERB and PER:CRY. This cycle segmentation is next characterized through a piecewise affine model, whose analytical study allows us to propose an Algorithm to generate biologically-consistent circadian oscillators. Our study provides a characterization of the cycle dynamics in terms of four fundamental threshold parameters and one scaling parameter, shows robustness of the circadian system and its period, and identifies critical points for correct cycle progression.
    Keywords:  Analytic solutions; Circadian clock cycle dynamics; Parameter regions; Period robustness; Periodic sequence of regions; Piecewise affine model
    DOI:  https://doi.org/10.1007/s00285-024-02164-y
  2. Bioessays. 2024 Dec 18. e202400211
    A Compensated Clock: Temperature and Nutritional Compensation Mechanisms Across Circadian Systems.
    Elizabeth-Lauren Stevenson, Adrienne K Mehalow, Jennifer J Loros, Christina M Kelliher, Jay C Dunlap.
      Circadian rhythms are ∼24-h biological oscillations that enable organisms to anticipate daily environmental cycles, so that they may designate appropriate day/night functions that align with these changes. The molecular clock in animals and fungi consists of a transcription-translation feedback loop, the plant clock is comprised of multiple interlocking feedback-loops, and the cyanobacterial clock is driven by a phosphorylation cycle involving three main proteins. Despite the divergent core clock mechanisms across these systems, all circadian clocks are able to buffer period length against changes in the ambient growth environment, such as temperature and nutrients. This defining capability, termed compensation, is critical to proper timekeeping, yet the underlying mechanism(s) remain elusive. Here we examine the known players in, and the current models for, compensation across five circadian systems. While compensation models across these systems are not yet unified, common themes exist across them, including regulation via temperature-dependent changes in post-translational modifications.
    Keywords:  Arabidopsis; Drosophila; Neurospora; circadian rhythms; cyanobacteria; nutritional compensation; temperature compensation
    DOI:  https://doi.org/10.1002/bies.202400211
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