Last Monday while in Amsterdam with my Mam and two sisters, a friend of mine sent a text to let me know that the 2017 Nobel Laureates in Physiology and Medicine were Hall, Rosbash and Young. They were awarded the Nobel for their work in identifying the key genes that create circadian or body clock rhythms in the fruit fly. My feet literally were stuck to the ground, it was thrilling to know that these gentlemen would get the recognition that they so deserve, but also what this will mean for the field of science that I am so passionate about. The body clock is the molecular timekeeping system that exists in practically every organism on the earth and in every cell in our body. Simply put, it allows the cell to tell what time of day it is. Why is that important? We live on a spinning planet and because of the earth’s rotation to the sun, all life on earth has been subjected to daily periods of light and heat, dark and cold. The body clock allows us to anticipate and respond to these 24-hour predictable environmental changes and synchronises our physiology to it. For example, the body clock increases cortisol levels in the body ahead of awakening, this helps us to become active once we wake. The body clock also increases expression of digestive enzymes in the intestinal tract during daylight hours (this is why curry chips at 3am is never a great idea!).
Back in the 80’s Hall, Rosbash and Young independently isolated a gene called Period, they showed how the gene encodes a protein PER that builds up in cells at night and degrades during the day. This daily rise and fall of PER essentially allow the cell to track time of day. How thrilling it must have been for them to observe this daily change in the mRNA levels of Period gene (Figure 1- black line), all that is changing along the x-axis is the time of day.
So what does this mean three decades later? We have made great strides in understanding how the molecular clock works. We now know that the clock keeps time by a series of transcriptional-translational feedback loops. We also know that the clock controls 40% of all coding genes within the body. The body clock controls all aspects of our physiology from metabolism to immunity.
Many diseases, such as osteoarthritis and cardiovascular disease, are highly time of day dependent. Moreover, it appears that disruption of our body clocks, caused by our non-stop 24/7 lifestyle and exposure to artificial light at all times of day, is partly responsible for the increase in chronic inflammatory diseases. Unfortunately, most cell culture systems are not synchronized with the time of day, and this, in my opinion, is one of the main reasons that many researchers unknowingly neglect this field. Finally, we are making great strides in attempting to time specific treatments to the right time of day, an area called chronotherapy. Therefore, it is my hope that this increased awareness of the body clock will bring more researchers into this fascinating field. If we don’t fully understand how our body clock controls physiology and disease we will certainly be left in the dark.
Annie Curtis is a Research Lecturer and runs the Immune Clock laboratory at MCT and is fascinated by all things body clock related.