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The 2017 Nobel Prize in Physiology or Medicine was awarded to Jeffrey C. Hall, Michael Rosbash and Michael W. Young for their elucidation of the molecular mechanisms controlling circadian rhythm. Their pioneering work in Drosophila uncovered the internal oscillators, or clocks, that synchronise cellular metabolism and organismal behaviour to the light/dark cycle to generate biological rhythms with 24 hour periodicity.
Plants contain several tissue-specific decentralized but communicating ‘clocks’. These control developmental outputs in response to environmental change: the vasculature clock for photoperiodic control of flowering, and the epidermis clock for temperature-dependent elongation.
Master circadian clocks in discrete neurons trigger profound daily changes in brain states, such as sleep and wake states. A study now finds a circuit through which these pacemakers act to control daily behavioral rhythms in Drosophila.
Many aspects of sleep, including the how and why, are still mysterious, especially its relationship to learning and memory. A new study suggests that sleep may serve to reset synaptic potentiation, linking it to homeostatic plasticity.
The Per2 gene is a core component of the circadian clock in mammals. It now seems that the mouse Per2 gene is also involved in suppressing tumours, through other genes that affect cell proliferation and death.
Circadian regulation of epigenetic chromatin marks drives daily transcriptional oscillation of thousands of genes and is intimately linked to cellular metabolism and bioenergetics. New work links circadian fluctuations in the activity of the SIRT1 deacetylase, a sensor of the cellular energy state, to histone-methylation changes and the circadian expression of clock-controlled genes.
The robustness of the circadian clock deteriorates with aging. Two new studies show that aging reprograms the circadian transcriptome in a cell-type-dependent manner and that such rewiring can be reversed by caloric restriction.