What makes some of us ‘night owls’, and others ‘early birds’ who are ready to go at the crack of dawn? This is because our bodies have an internal ‘clock’ that regulates a complex series of biorhythms including sleep and wakefulness, fatigue, and cognitive ability. Earth works on a 24-hour cycle of night and day, and all organisms need to pace their activities to stay in line with this sequence. Our body clock though runs on a circadian cycle that is slightly longer than 24 hours. So it must constantly reset itself to the local hours of daylight, as otherwise it will continue to run slower and slower until it ends up expecting us to sleep for eight hours during the day and be awake during the night!
For years, scientists believed that this biological timepiece was located only in our heads, somewhere in the superchiasmatic nucleus — a region in the brain’s hypothalamus. It controlled the cycles by responding to light that travels from our eyes to our brain, orienting our bodies to day-time alertness and night-time sleep. Later research on ‘period genes’ (that turn cells into bio-clocks by switching specific genes on and off), however, showed that not only the head, but also the whole body is involved in keeping us on a regular 24-hour timetable. Besides driving our sleep-wake cycle, this clock also regulates hormone levels, body temperature, and blood pressure. Disease resets this timepiece, triggering abnormal cell division in the body and influencing symptoms. Which is why some drugs work better when administered at certain times of the day and doctors run tests at different times to get a more accurate diagnosis.
Although researchers identified several key components of the body clock, they could never figure out the actual mechanism that it uses to set itself to ‘local time’. But the latest findings of scientists from the Vanderbilt University in the US show that our biological timepieces work at the molecular level. It is the attachment and detachment of phosphate groups (phosphorylation and dephosphorylation) for regulating proteins in the cell that allow the bio-clock to turn cellular processes on and off. Now that this elegant nano-machine that makes our internal clocks tick has been identified, it may not be long before scientists learn how to reset them and develop new therapies for anything from jet lag to sleep problems in shift workers, and even cancer.