MicroRNA mutant turns back the evolutionary clock for fly olfaction

In a recent paper, Cayirlioglu et al. report that the disruption of a specific miRNA, miR-279, which normally acts to inhibit the transcription factor Nerfin-1, uncovers a population of hybrid CO₂ neurons in the Drosophila maxillary palp.1 Normally, fruit fly CO₂ neurons are found only in the antennae, while mosquito CO₂ neurons are found only in the maxillary palps. The hybrid neurons in this miRNA mutant may, thus, recapitulate an evolutionary intermediate unseen since the divergence of these two dipteran lineages over 250 million years ago. BioEssays 30:621-623, 2008.