Amnesiac Is Required in the Adult Mushroom Body for Memory Formation.

It was proposed that the gene () is required for consolidation of aversive memory in the dorsal paired medial (DPM) neurons, a pair of large neurons that broadly innervate the mushroom bodies (MB), the fly center for olfactory learning and memory (Waddell et al., 2000). Yet, a conditional analysis showed that it was not possible to rescue the memory deficit of null mutant flies when expression was restored only in the adult (DeZazzo et al., 1999), which led the authors to suggest that might be involved in the development of brain structures that normally promote adult olfactory memory. To further investigate temporal and spatial requirements of Amnesiac (AMN) peptide in memory, we used RNA interference in combination with conditional drivers. Experiments were conducted either in both sexes, or in either sexes. Our data show that acute modulation of expression in adult DPM neurons does not impact memory. We further show that expression is required for normal development of DPM neurons. Detailed enhancer trap analyses suggest that transcription unit contains two distinct enhancers, one specific of DPM neurons, and the other specific of α/β MB neurons. This prompted us to investigate extensively the role of AMN in the adult MB. Together, our results demonstrate that is acutely required in adult α/β MB neurons for middle-term and long-term memory. The data thus establish that plays two distinct roles. Its expression is required in DPM neurons for their development, and in adult MB for olfactory memory. The gene encodes a neuropeptide whose expression was proposed to be required for consolidation of aversive memory in the dorsal paired medial (DPM) neurons, a pair of large neurons that broadly innervate the mushroom bodies (MB), the olfactory memory center. Here, we investigated temporal and spatial requirement using conditional tools that allowed us to manipulate its expression in selected neurons. This work leads to a complete reassessment of the role of in brain development and memory. We show that is required for two distinct processes: for normal development of DPM neurons, and in adult MB for memory.