Sleep and memory consolidation are linked by RNA processing genes in the Drosophila mushroom body

Abstract

Memory consolidation in Drosophila can be sleep-dependent or sleep- independent, depending on the availability of food. Different regions of the mushroom body (MB) mediate these two mechanisms, with the ap α’/β’ neurons required for sleep- dependent memory consolidation in flies that are fed after training. These neurons are also involved in the increase of sleep after training, suggesting a link between sleep and memory. To better understand the mechanisms underlying sleep and memory consolidation initiation, we analyzed the transcriptome of ap α’/β’ neurons one hour after appetitive memory conditioning. A small number of genes were differentially expressed specifically in flies fed after training, but not in trained and starved flies or untrained flies. Knockdown of each of these differentially expressed genes in the ap α’/β’ neurons revealed multiple genes that affect sleep, with notable effects observed for Polr1F and Regnase-1, both of which decrease in expression after conditioning. Knockdown of Polr1F, a regulator of ribosome RNA transcription, in adult flies promotes sleep and increases pre-ribosome RNA expression as well as overall translation, supporting a function for Polr1F downregulation in memory consolidation. Conversely, knockdown of Regnase-1, an mRNA decay protein localized to the ribosome, reduces sleep. Given that Regnase-1 knockdown in ap α’/β’ neurons affects both sleep-dependent and sleep- independent memory, as well as short-term memory, Regnase-1 likely has an early role in the learning process, which may obscure a later function for its downregulation during sleep-dependent memory. These findings indicate that changes in RNA processing play a crucial role in triggering post-training sleep and memory consolidation.