Lobe‐Less, a Long Noncoding <scp>RNA</scp> That Regulates <scp> <i>Drosophila</i> </scp> Mushroom Body Morphogenesis

Long noncoding RNAs (lncRNAs) are abundantly transcribed in eukaryotes, but most of their physiological roles, especially in neural development, remain unclear due to limited in vivo studies. Here we show that Lobe-less (LOL) lncRNA of Drosophila is expressed in developing neuronal cells and is required for the development of the mushroom body, a center of memory and learning in the insect brain. lol mutant flies exhibit defective morphology of the mushroom body and axon branch patterns, as well as misregulation of neurogenic genes. LOL RNA forms nuclear puncta and genetically interacts with Polycomb group genes in the regulation of homeotic genes. These findings demonstrate that this long ncRNA plays a critical role in the epigenetic control of neural circuit formation.