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Circadian clocks in human red blood cells

Nature volume 469, pages 498503 (27 January 2011) | Download Citation

Abstract

Circadian (24 hour) clocks are fundamentally important for coordinated physiology in organisms as diverse as cyanobacteria and humans. All current models of the molecular circadian clockwork in eukaryotic cells are based on transcription–translation feedback loops. Non-transcriptional mechanisms in the clockwork have been difficult to study in mammalian systems. We circumvented these problems by developing novel assays using human red blood cells, which have no nucleus (or DNA) and therefore cannot perform transcription. Our results show that transcription is not required for circadian oscillations in humans, and that non-transcriptional events seem to be sufficient to sustain cellular circadian rhythms. Using red blood cells, we found that peroxiredoxins, highly conserved antioxidant proteins, undergo 24-hour redox cycles, which persist for many days under constant conditions (that is, in the absence of external cues). Moreover, these rhythms are entrainable (that is, tunable by environmental stimuli) and temperature-compensated, both key features of circadian rhythms. We anticipate that our findings will facilitate more sophisticated cellular clock models, highlighting the interdependency of transcriptional and non-transcriptional oscillations in potentially all eukaryotic cells.

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Acknowledgements

This work was supported by the Wellcome Trust (083643/Z/07/Z), the MRC Centre for Obesity and Related metabolic Disorders (MRC CORD) and the NIHR Cambridge Biomedical Research Centre. We thank M. Jain and R. Edgar for discussions about the manuscript, A. Coles and J. Jones for providing access to samples, and G. van der Horst and F. Tamanini for providing access to Cry1 Cry2 knockout (and wild-type) mouse embryonic fibroblasts.

Author information

Affiliations

  1. Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Addenbrooke’s Hospital, Cambridge CB2 0QQ, UK

    • John S. O’Neill
    •  & Akhilesh B. Reddy

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Contributions

A.B.R. and J.S.O’N. conceived, designed and performed the experiments, and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Akhilesh B. Reddy.

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    Supplementary Information

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https://doi.org/10.1038/nature09702

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