In a small pause during the day, I was thinking about the mechanisms behind the daily activities of living beings. Who regulates a regulatory gene? How is a certain process initiated? Or, to be more clear, which came first, the egg or the chicken?
The systematists would say it’s the egg, stemming from a primitive common ancestor that existed between birds and reptiles. But since taxonomy and biological classification really do not allow me much navigation, I won’t risk any more guesses. But thinking about the moment I woke up, was it just the alarm clock that caused the discord?
Certainly not. Our body prepares for awakening. In the last post, we discussed the synchronization of biological processes with the temporal variations of the environment, and because of this, upon waking, the levels of the hormone melatonin are already lower while cortisol levels are higher.
But how does light information coordinate the induction of rhythm in the pacemaker neurons that, in turn, will drive the daily rhythms?
Marc Ruben, from the Department of Biology at New York University, studied a gene that encodes potassium channels, important for maintaining the quiescent state of pacemaker neurons, and whose expression is increased at dusk. Thus, the oscillations of the circadian rhythm influence the decrease in the expression of these genes, affecting the neurons that modulate, in an integrated manner with other systems, the activities of the entire body.
However, this knowledge is recent and has been built by breaking paradigms.
Not long ago, it was believed that the giant DNA sequence was divided into 2 parts: one coding and the other that would be junk. However, in the pineal gland, a structure whose hormonal production is controlled by the cycle of environmental lighting, long active sequences of DNA were discovered that were previously classified as inert material.
David Klein and collaborators used next-generation sequencing technology to find the so-called long non-coding RNA (lncRNA) in the tissue of the pineal gland. Unlike classical RNA sequences, lncRNA is involved in the activation, blocking, or even alteration of gene or protein activity and not just serving as a template for protein manufacturing. These sequences are distinctly activated during light and dark periods, and are produced much more in the tissues of the pineal gland than in the rest of the body. The exact role of lncRNA is still unknown, but its importance in relation to the circadian rhythm is clear.
Every time I encounter this complexity of chronobiology, I find the potential for connection and synchronization between molecules and the environment intriguing. It makes me advance in questioning, thinking about the largest organ in our body formed by various cell types that is in direct contact with the external and internal environment: the skin. How does this synchronization of physiological responses work among the different cell types and the body?
Each skin cell, such as fibroblasts, keratinocytes, and melanocytes, has its biological clocks, whose clock genes are regulated by environmental changes and act in different and alternating phases leading to the rhythmic functioning of the cells of the organ. It is possible that this system called multi-oscillator, under the command of the central biological clock, is related to the fine-tuning of the physiological reactions that occur in the skin in response to the adversities faced by the action of external agents (Sandu, et al, 2012).
These data are recent, opening up space for more discussions and studies regarding the control of biological rhythm and the synchronization of responses among the cells present in different organs.
In any case, it is clear that different light intensities trigger different responses in our body. Thus, remember chronobiology when following medical instructions and recommendations for products that may shorten or treat the signs caused by external agents. The nighttime product is not there by chance.
References
Coon SL, Munson PJ, Cherukuri PF, Sugden D, Rath MF, Møller M, Clokie SJ, Fu C, Olanich ME, Rangel Z, Werner T; NISC Comparative Sequencing Program, Mullikin JC, Klein DC. Circadian changes in long noncoding RNAs in the pineal gland. Proc Natl Acad Sci U S A. 2012 Aug 14;109(33):13319-24. Epub 2012 Aug 3.
Marc Ruben, Mark D. Drapeau, Dogukan Mizrak, and Justin Blau. A Mechanism for Circadian Control of Pacemaker Neuron Excitability. Journal of Biological Rhythms, 2012; 27: 353-364.
Sandu C, Dumas M, Malan A, Sambakhe D, Marteau C, Nizard C, Schnebert S, Perrier E, Challet E, Pévet P, Felder-Schmittbuhl MP. Human skin keratinocytes, melanocytes, and fibroblasts contain distinct circadian clock machineries. Cell Mol Life Sci. 2012 Oct;69(19):3329-39. Epub 2012 May 25.
