It was suspected for centuries and confirmed by scientific studies decades ago – animals, including human beings, have internal ‘clocks.’ That is, many of our biological processes run on a schedule, and that schedule is maintained by some kind of biological equivalent to a clock. Now, in work that is highly characteristic of ‘the molecular biology revolution’ of the late 20th and early 21st centuries, researchers at Hebrew University (New York, USA) have isolated the genetic mechanism behind at least one kind of biological clock…
The field of chronobiology (the science of periodic and cyclic phenomena in living creatures) was developed during the 1960’s, although the history of scientific interest in the 24 hour cycle in plants and animals dates back to the 18th century. What is now called the circadian rhythm, corresponding to the 24 hours of an Earth day, is one mechanism by which living things can orient internal processes with physical reality. With an internal clock the hours for feeding, resting and other activities can be more or less synchronized with events such as daylight and darkness. Even some forms of bacteria, for example cyanobacteria (blue-green algae), have demonstrated a circadian clock.
The sleep-wake cycle, the most characterized manifestation of the circadian clock, is generated thanks to specialized neurons found both in humans and fruitflies. (The mechanism governing the circadian clock in fruitflies is almost identical to the one mammals — and humans — have.)
These neurons have the striking capability of counting time very accurately via a complex process of gene activation and repression that result in a tightly controlled process that takes exactly 24 hours.
The new research by Dr. Kadener and his colleagues, published in an article in the journal Genes and Development (and that was highlighted in Nature Review Neuroscience), has shown that a new mode of regulation has a pivotal importance for the ability of our internal clock to accurately count those 24 hours each day. Specifically, they have shown that the very tiny miRNA [microRNA, single stranded RNA molecules, which regulate gene expression] are necessary for the circadian rhythms to function.
MiRNAs have recently been discovered and have been shown to be involved in different processes in animals. By the use of new state-of-the-art techniques (most of them developed in the present study) the authors demonstrate that one specific miRNA (called bantam) recognizes and regulates the translation of the gene clock. This constitutes the first example of a defined miRNA-gene regulation in the central clock.
[Source: Hebrew University]