Mushroom Body Specific Transcriptome Analysis Reveals Dynamic Regulation of Learning and Memory Genes After Acquisition of Long-Term Courtship Memory in Drosophila
Abstract:The formation and recall of long-term memory (LTM) requires neuron activity-induced gene expression. Transcriptome analysis has been used to identify genes that have altered expression after memory acquisition, however, we still have an incomplete picture of the transcriptional changes that are required for LTM formation. The complex spatial and temporal dynamics of memory formation creates significant challenges in defining memory-relevant gene expression changes. The Drosophila mushroom body (MB) is a signal… Show more
“…MB specificity was achieved using the Gal4 driver R14H06-Gal4 from the Janelia FlyLight collection (Jenett et al, 2012), which is primarily expressed in post-mitotic cells contributing to the γ and α/β lobes of the adult MB (Fig. 2A; ) (Jones et al, 2018). Fig.…”
Technology has led to rapid progress in the identification of genes involved in neurodevelopmental disorders such as intellectual disability (ID), but our functional understanding of the causative genes is lagging. Here, we show that the SWI/SNF chromatin remodelling complex is one of the most over-represented cellular components disrupted in ID. We investigated the role of individual subunits of this large protein complex using targeted RNA interference in post-mitotic memory-forming neurons of the
Drosophila
mushroom body (MB). Knockdown flies were tested for defects in MB morphology, short-term memory and long-term memory. Using this approach, we identified distinct roles for individual subunits of the
Drosophila
SWI/SNF complex. Bap60, Snr1 and E(y)3 are required for pruning of the MBγ neurons during pupal morphogenesis, while Brm and Osa are required for survival of MBγ axons during ageing. We used the courtship conditioning assay to test the effect of MB-specific SWI/SNF knockdown on short- and long-term memory. Several subunits, including Brm, Bap60, Snr1 and E(y)3, were required in the MB for both short- and long-term memory. In contrast, Osa knockdown only reduced long-term memory. Our results suggest that individual components of the SWI/SNF complex have different roles in the regulation of structural plasticity, survival and functionality of post-mitotic MB neurons. This study highlights the many possible processes that might be disrupted in SWI/SNF-related ID disorders. Our broad phenotypic characterization provides a starting point for understanding SWI/SNF-mediated gene regulatory mechanisms that are important for development and function of post-mitotic neurons.
“…MB specificity was achieved using the Gal4 driver R14H06-Gal4 from the Janelia FlyLight collection (Jenett et al, 2012), which is primarily expressed in post-mitotic cells contributing to the γ and α/β lobes of the adult MB (Fig. 2A; ) (Jones et al, 2018). Fig.…”
Technology has led to rapid progress in the identification of genes involved in neurodevelopmental disorders such as intellectual disability (ID), but our functional understanding of the causative genes is lagging. Here, we show that the SWI/SNF chromatin remodelling complex is one of the most over-represented cellular components disrupted in ID. We investigated the role of individual subunits of this large protein complex using targeted RNA interference in post-mitotic memory-forming neurons of the
Drosophila
mushroom body (MB). Knockdown flies were tested for defects in MB morphology, short-term memory and long-term memory. Using this approach, we identified distinct roles for individual subunits of the
Drosophila
SWI/SNF complex. Bap60, Snr1 and E(y)3 are required for pruning of the MBγ neurons during pupal morphogenesis, while Brm and Osa are required for survival of MBγ axons during ageing. We used the courtship conditioning assay to test the effect of MB-specific SWI/SNF knockdown on short- and long-term memory. Several subunits, including Brm, Bap60, Snr1 and E(y)3, were required in the MB for both short- and long-term memory. In contrast, Osa knockdown only reduced long-term memory. Our results suggest that individual components of the SWI/SNF complex have different roles in the regulation of structural plasticity, survival and functionality of post-mitotic MB neurons. This study highlights the many possible processes that might be disrupted in SWI/SNF-related ID disorders. Our broad phenotypic characterization provides a starting point for understanding SWI/SNF-mediated gene regulatory mechanisms that are important for development and function of post-mitotic neurons.
“…Several previous studies have used genome-wide methods to profile expression in the Drosophila MB (Perrat et al 2013; Crocker et al 2016; Croset et al 2018; Davie et al 2018; Jones et al 2018). Perrat et al used a microarray-based approach to profile expression of each of the three major classes of MB KCs (purified by flow cytometry from dissociated brains) and compared these profiles with expression in the rest of the brain.…”
The insect mushroom body (MB) is a conserved brain structure that plays key roles in a diverse array of behaviors. The Drosophila melanogaster MB is the primary invertebrate model of neural circuits related to memory formation and storage, and its development, morphology, wiring, and function has been extensively studied. MBs consist of intrinsic Kenyon Cells that are divided into three major neuron classes (γ, α′/β′ and α/β) and 7 cell subtypes (γd, γm, α′/β′ap, α′/β′m, α/βp, α/βs and α/βc) based on their birth order, morphology, and connectivity. These subtypes play distinct roles in memory processing, however the underlying transcriptional differences are unknown. Here, we used RNA sequencing (RNA-seq) to profile the nuclear transcriptomes of each MB neuronal cell subtypes. We identified 350 MB class- or subtype-specific genes, including the widely used α/β class marker Fas2 and the α′/β′ class marker trio. Immunostaining corroborates the RNA-seq measurements at the protein level for several cases. Importantly, our data provide a full accounting of the neurotransmitter receptors, transporters, neurotransmitter biosynthetic enzymes, neuropeptides, and neuropeptide receptors expressed within each of these cell types. This high-quality, cell type-level transcriptome catalog for the Drosophila MB provides a valuable resource for the fly neuroscience community.
“…Similar approaches have also been used in Drosophila , Aplysia , and C. elegans . In Drosophila , selected cells involved in learning and memory were picked either by patch clamp or tagged nuclei (INTACT) to obtain cell‐type‐specific transcriptomic profiles. Although these approaches can identify targets involved in these contexts, it has its limitations.…”
Consolidation of long‐term memory is a highly and precisely regulated multistep process. The transcription regulator cAMP response element‐binding protein (CREB) plays a key role in initiating memory consolidation. With time processing, first the cofactors are changed and, secondly, CREB gets dispensable. This ultimately changes the expressed gene program to genes required to maintain the memory. Regulation of memory consolidation also requires epigenetic mechanisms and control at the RNA level. At the neuronal circuit level, oscillation in the activity of CREB and downstream factor define engram cells. Together the combination of all regulation mechanisms allows correct memory processing while keeping the process dynamic and flexible to adjust to different contexts. Also see the video abstract here https://youtu.be/BhSCSmorpEc.
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