2017 Nobel Prize in Physiology or Medicine
Reason for Award
for the discovery of molecular mechanisms controlling the circadian rhythm
Laureates
United States of America
United States of America
United States of America
Explanation
Our bodies wake up in the morning and get sleepy at night because of an inner “body clock.” In 2017, three scientists won the Nobel Prize for finding out how this clock works. Using tiny fruit flies, they discovered a gene called “period.” The protein made from this gene grows and shrinks like the hands of a clock. When a lot of the protein builds up, it turns its own gene off; when the protein disappears, the gene turns on again. This on-and-off cycle takes about 24 hours, creating the rhythm of a day. The same trick is used in people and many other living things, so their work helped unlock the secret of our daily rhythm.
Related Keywords
circadian rhythm
A set of physiological and behavioral changes that repeat roughly every 24 hours. It is synchronized with Earth’s rotation and governs sleep–wake cycles, hormone release, body temperature and more. The rhythm persists in constant conditions, indicating an internal clock, but its phase is reset by zeitgebers such as light and temperature. It is evolutionarily conserved from bacteria to plants and animals. Disruption of the rhythm increases risks for obesity, diabetes, cancer and psychiatric disorders.
period gene
The first clock gene identified in Drosophila. It encodes the PER protein, which suppresses its own transcription once it accumulates, forming a negative feedback loop. Nonsense mutations abolish rhythmicity, whereas missense mutations shorten or lengthen the period—classic evidence linking genotype to behavior. Mammals possess PER1-PER3 homologs; mutations in these genes cause sleep phase disorders. Study of period laid the foundation for modern molecular clock models and led to discovery of additional clock genes.
timeless gene
A clock gene discovered by Young; it encodes the TIM protein. TIM binds PER to form a complex that enters the nucleus and fully represses transcription. Light-activated CRY targets TIM for degradation, providing photic input into the clock. tim mutants abolish PER cycling and produce arrhythmic behavior. In mammals, TIM’s role is partly replaced by CRY proteins, illustrating evolutionary divergence of the core mechanism.
transcription-translation feedback loop (TTFL)
A model in which transcription of clock genes and translation of their proteins form a closed, self-inhibitory loop with intrinsic delay. In flies PER/TIM and in mammals PER/CRY constitute the negative arm, while CLK/CYC or CLOCK/BMAL1 drive transcription as the positive arm. Post-translational events—phosphorylation, ubiquitination, nuclear export—act as delay elements that stretch the cycle to 24 hours. The TTFL concept extends to plants and fungi, making it a universal principle, although non-transcriptional clocks (e.g., cyanobacterial KaiC system) provide contrasting mechanisms that enrich chronobiology.
clock gene
A collective term for genes indispensable for generating or maintaining circadian rhythms—e.g., per, tim, clock, cycle, doubletime, cryptochrome. They regulate one another at transcriptional and translational levels and form protein complexes that produce oscillations. In mammals, CLOCK, BMAL1, PER, CRY and CK1δ/ε are central components. Clock genes cross-talk with metabolic pathways and cell-cycle genes, forming a body-wide temporal control network. Mutations linked to human diseases are continually being identified, opening avenues for precision medicine.
Drosophila melanogaster
A dipteran insect studied for over a century as a genetic model. Advantages include short generation time, abundant mutant lines and a detailed genetic map. Behavioral studies of clock mutants by Benzer and Konopka launched molecular chronobiology. About 150 clock neurons in its CNS display PER/TIM oscillations. Drosophila shares many gene homologs with humans and serves as a platform for drug screening and neurobehavioral research.
suprachiasmatic nucleus (SCN)
A bilateral pair of tiny nuclei in the hypothalamus that serve as the mammalian “master clock.” They receive photic input from the retina and synchronize peripheral clocks by neural and hormonal outputs. Roughly 20,000 neurons are coupled electrically and chemically, ensuring intercellular synchrony. Ablation abolishes behavioral rhythms, yet autonomous rhythms persist in peripheral tissues, establishing a hierarchical clock network. In humans, slow SCN re-entrainment underlies jet lag and shift-work health issues.