Three Americans win 2017 Nobel Prize in medicine for research on circadian clocks

       Jeffrey C. Hall, Michael Rosbash and Michael W. Young won the 2017 Nobel Prize in physiology or medicine on Monday for their research into what controls circadian rhythms — the internal clock that governs how humans, animals and plants behave throughout the day and night.
       Thanks in part to their discoveries, scientists and doctors now know these day-and-night cycles keep creatures alive by regulating our alertness, sleep patterns, blood pressure, hormones, body temperature and when we eat.
      Our circadian clock helps to regulate sleep patterns, feeding behavior, hormone release, blood pressure and body temperature. A large proportion of our genes are regulated by the clock. Illustration by Jeffrey C. Hall, Michael Rosbash and Michael W. Young (left to right) won the 2017 Nobel Prize for physiology and medicine. Illustrations by the Nobel Assembly at the Karolinska Institutet.
      Scientists had known about circadian rhythms since 1729, when astronomer Jean Jacques d’Ortous de Mairan placed a mimosa plant into a dark room and noticed that the plant’s leaves still opened and closed at the same times every day.
Through a series of breakthroughs, Hall, Rosbash and Young showed these internal clocks are self-regulated. In the morning, sunlight switches on the “period” gene, which begins to produce its protein. This protein accumulates in the cytoplasm, the chunky space in our cells that surrounds the nucleus where our DNA and the period gene are housed.
        Hall and Rosbash found that period proteins built up throughout the day until nightfall, when their levels began to gradually drop. When dawn broke, period proteins disappeared, and the cycle repeated itself. They hypothesized that the period protein was somehow crossing into the nucleus to shut off its own gene, in what they dubbed a transcription-translation feedback loop. Young extended the work by uncovering two additional protein, named “timeless,” which was responsible to escorting the period protein into the nucleus. Young’s lab also identified a third protein — called double-time — that controlled the timing of the destruction of the period proteins.
      Their combined work launched a subgenre of molecular biology that focused on circadian rhythm proteins. Though the genes differ from species to species, transcription-translation feedback networks for circadian rhythms were ultimately found in a bevy of organisms — from algae to plants to Homo sapiens.
       In humans, these clock genes control the production of insulin and other hormones involved in maintaining how our bodies process food. Disruption of the genes through sleep deprivation or mutation alters brain functions and has been tied to sleep disorders, depression, bipolar disorder and memory defects. Out of whack circadian rhythms also increase a person’s risk for cancer, obesity, diabetes and other metabolic disorders.