Ancient Tweaking

Twenty years ago, scientists knew nothing of the scraps of RNA that are now known to influence just about every process in our bodies. Back then, the textbooks were simpler: genes code for proteins via the intermediate of RNA, and proteins called transcription factors regulate other proteins. This recipe was so entrenched in the basic orthodoxy of molecular biology that it was even given the name ‘the central dogma’ by the co-discoverer of DNA, Francis Crick.

Scientists now know, however, that this classic view of protein regulation is far too blunderingly inefficient for evolution to settle for. At some point hundreds of millions of years ago, the generation of a small stretch of RNA that could tweak this process gave an individual the edge over everyone else. And so regulatory RNA was born. These scraps of RNA – on average only 22 nucleotides long and now dubbed microRNAs, or miRNAs for short – bind to some messenger RNAs and label them for inactivation or destruction.

So far thousands of miRNAs have been identified in animals. These superintendents of protein regulation are involved in the earliest stages of an animal’s development, determining which cell types grow where and when, and how these cells differentiate into the different body parts. However, since the discovery of miRNAs, many scientists have wondered whether the same miRNAs govern specific tissues in different animals. Knowing this would not only give clues to the age of these different miRNAs, but
also to the age of the cells in which they are found.

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