Early Origin Indicated For Small RNAs

MicroRNAs (miRNAs), which are small RNA molecules involved in gene regulation, appear to have evolved in the earliest animals, a study published in Nature suggests (DOI: 10.1038/nature07415). Until now, biologists have not known whether miRNAs are found only in species with bilateral symmetry, such as humans, flies, and worms. A team led by biologist David P. Bartel of the Whitehead Institute for Biomedical Research and MIT reports that miRNAs and Piwi-interacting RNAs (piRNAs), which are small RNAs thought to protect germ cells from transposons (mobile genetic segments), exist in simpler animals such as Nematostella vectensis (the starlet sea anemone) and Amphimedon queenslandica (a type of sponge). The team found 40 miRNAs in the anemone and eight miRNAs in the sponge. The anemone and sponge produce both known kinds of piRNA. The researchers propose that miRNAs and piRNAs "might have helped to usher in the era of multicellular life."