@article {69985, title = {Cross-species comparative connectomics reveals the evolution of an olfactory circuit}, journal = {bioRxiv}, year = {2025}, month = {2025 Jun 11}, abstract = {

Animal behavioural diversity ultimately stems from variation in neural circuitry, yet how central neural circuits evolve remains poorly understood. Studies of neural circuit evolution often focus on a few elements within a network. However, addressing fundamental questions in evolutionary neuroscience, such as whether some elements are more evolvable than others, requires a more global and unbiased approach. Here, we used synapse-level comparative connectomics to examine how an entire olfactory circuit evolves. We compared the full antennal lobe connectome of the larvae of two closely related Drosophila species, D. melanogaster and D. erecta, which differ in their ecological niches and odour-driven behaviours. We found that evolutionary change is unevenly distributed across the network. Some features, including neuron types, neuron numbers and interneuron-to-interneuron connectivity, are highly conserved. These conserved elements delineate a core circuit blueprint presumably required for fundamental olfactory processing. Superimposed on this scaffold, we find rewiring changes that mirror each species ecologies, including a systematic shift in the excitation-to-inhibition balance in the feedforward pathways. We further show that some neurons have changed more than others, and that even within individual neurons some synaptic elements remain conserved while others display major species-specific changes, suggesting evolutionary hot-spots within the circuit. Our findings reveal constrained and adaptable elements within olfactory networks, and establish a framework for identifying general principles in the evolution of neural circuits underlying behaviour.

}, doi = {10.1101/2025.06.11.659158}, url = {https://www.biorxiv.org/content/early/2025/06/11/2025.06.11.659158}, author = {Roberts, Ruairi and Giez, Christoph and Dhawan, Serene and Pang, Song and Randel, Nadine and Zhiyuan, Lu and Gong, Hui and Dekens, Leonard and DiFrisco, James and Xu, C Shan and Hess, Harald and Zlatic, Marta and Cardona, Albert and Prieto-Godino, Lucia L.} } @article {67793, title = {Circuits for integrating learned and innate valences in the insect brain.}, journal = {eLife}, volume = {10}, year = {2021}, month = {2021 Nov 10}, abstract = {

Animal behavior is shaped both by evolution and by individual experience. Parallel brain pathways encode innate and learned valences of cues, but the way in which they are integrated during action-selection is not well understood. We used electron microscopy to comprehensively map with synaptic resolution all neurons downstream of all Mushroom Body output neurons (encoding learned valences) and characterized their patterns of interaction with Lateral Horn neurons (encoding innate valences) in larva. The connectome revealed multiple types that receive convergent Mushroom Body and Lateral Horn inputs. A subset of these receives excitatory input from positive-valence MB and LH pathways and inhibitory input from negative-valence MB pathways. We confirmed functional connectivity from LH and MB pathways and behavioral roles of two of these neurons. These neurons encode integrated odor value and bidirectionally regulate turning. Based on this we speculate that learning could potentially skew the balance of excitation and inhibition onto these neurons and thereby modulate turning. Together, our study provides insights into the circuits that integrate learned and innate valences to modify behavior.

}, issn = {2050-084X}, doi = {10.7554/eLife.62567}, author = {Eschbach, Claire and Fushiki, Akira and Winding, Michael and Afonso, Bruno and Andrade, Ingrid V and Cocanougher, Benjamin T and Eichler, Katharina and Gepner, Ruben and Si, Guangwei and Valdes-Aleman, Javier and Fetter, Richard D and Gershow, Marc and Jefferis, Gregory Sxe and Samuel, Aravinthan Dt and Truman, James W and Cardona, Albert and Zlatic, Marta} } @article {65810, title = {Comparative Connectomics Reveals How Partner Identity, Location, and Activity Specify Synaptic Connectivity in Drosophila.}, journal = {Neuron}, volume = {109}, year = {2021}, month = {2021 Jan 06}, pages = {105-22}, abstract = {

The mechanisms by which synaptic partners recognize each other and establish appropriate numbers of connections during embryonic development to form functional neural circuits are poorly understood. We combined electron microscopy reconstruction, functional imaging of neural activity, and behavioral experiments to elucidate the roles of (1) partner identity, (2) location, and (3) activity in circuit assembly in the embryonic nerve cord of Drosophila. We found that postsynaptic partners are able to find and connect to their presynaptic partners even when these have been shifted to ectopic locations or silenced. However, orderly positioning of axon terminals by positional cues and synaptic activity is required for appropriate numbers of connections between specific partners, for appropriate balance between excitatory and inhibitory connections, and for appropriate functional connectivity and behavior. Our study reveals with unprecedented resolution the fine connectivity effects of multiple factors that work together to control the assembly of neural circuits.

}, issn = {1097-4199}, doi = {10.1016/j.neuron.2020.10.004}, author = {Valdes-Aleman, Javier and Fetter, Richard D and Sales, Emily C and Heckman, Emily L and Venkatasubramanian, Lalanti and Doe, Chris Q and Landgraf, Matthias and Cardona, Albert and Zlatic, Marta} } @article {67225, title = {Comparative single-cell transcriptomics of complete insect nervous systems}, journal = {bioRxiv}, year = {2020}, month = {01/2020}, abstract = {

Molecular profiles of neurons influence information processing, but bridging the gap between genes, circuits, and behavior has been very difficult. Furthermore, the behavioral state of an animal continuously changes across development and as a result of sensory experience. How behavioral state influences molecular cell state is poorly understood. Here we present a complete atlas of the Drosophila larval central nervous system composed of over 200,000 single cells across four developmental stages. We develop polyseq, a python package, to perform cell-type analyses. We use single-molecule RNA-FISH to validate our scRNAseq findings. To investigate how internal state affects cell state, we optogentically altered internal state with high-throughput behavior protocols designed to mimic wasp sting and over activation of the memory system. We found nervous system-wide and neuron-specific gene expression changes. This resource is valuable for developmental biology and neuroscience, and it advances our understanding of how genes, neurons, and circuits generate behavior.

}, doi = {10.1101/785931}, url = {https://www.biorxiv.org/content/early/2020/01/16/785931}, author = {Cocanougher, Benjamin T. and Wittenbach, Jason D. and Long, Xi Salina and Kohn, Andrea B. and Norekian, Tigran P. and Yan, Jinyao and Colonell, Jennifer and Masson, Jean-Baptiste and Truman, James W. and Cardona, Albert and Turaga, Srinivas C. and Singer, Robert H. and Moroz, Leonid L. and Zlatic, Marta} } @article {48720, title = {The complete connectome of a learning and memory centre in an insect brain.}, journal = {Nature}, volume = {548}, year = {2017}, month = {2017 Aug 09}, pages = {175-182}, abstract = {

Associating stimuli with positive or negative reinforcement is essential for survival, but a complete wiring diagram of a higher-order circuit supporting associative memory has not been previously available. Here we reconstruct one such circuit at synaptic resolution, the Drosophila larval mushroom body. We find that most Kenyon cells integrate random combinations of inputs but that a subset receives stereotyped inputs from single projection neurons. This organization maximizes performance of a model output neuron on a stimulus discrimination task. We also report a novel canonical circuit in each mushroom body compartment with previously unidentified connections: reciprocal Kenyon cell to modulatory neuron connections, modulatory neuron to output neuron connections, and a surprisingly high number of recurrent connections between Kenyon cells. Stereotyped connections found between output neurons could enhance the selection of learned behaviours. The complete circuit map of the mushroom body should guide future functional studies of this learning and memory centre.

}, issn = {1476-4687}, doi = {10.1038/nature23455}, author = {Eichler, Katharina and Li, Feng and Litwin-Kumar, Ashok and Park, Youngser and Andrade, Ingrid and Schneider-Mizell, Casey M and Saumweber, Timo and Huser, Annina and Eschbach, Claire and Gerber, Bertram and Fetter, Richard D and Truman, James W and Priebe, Carey E and Abbott, L F and Thum, Andreas S and Zlatic, Marta and Cardona, Albert} } @article {47935, title = {Competitive disinhibition mediates behavioral choice and sequences in Drosophila.}, journal = {Cell}, volume = {167}, year = {2016}, month = {2016 Oct 5}, pages = {858-70}, abstract = {

Even a simple sensory stimulus can elicit distinct innate behaviors and sequences. During sensorimotor decisions, competitive interactions among neurons that promote distinct behaviors must ensure the selection and maintenance of one behavior, while suppressing others. The circuit implementation of these competitive interactions is still an open question. By combining comprehensive electron microscopy reconstruction of inhibitory interneuron networks, modeling, electrophysiology, and behavioral studies, we determined the circuit mechanisms that\ contribute to the Drosophila larval sensorimotor decision to startle, explore, or perform a sequence of the two in response to a mechanosensory stimulus. Together, these studies reveal that, early in sensory processing, (1) reciprocally connected feedforward inhibitory interneurons implement behavioral choice, (2) local feedback disinhibition provides positive feedback that consolidates and maintains the chosen behavior, and (3) lateral disinhibition promotes sequence transitions. The combination of these interconnected circuit motifs can implement both behavior selection and the serial organization of behaviors into a sequence.

}, issn = {1097-4172}, doi = {10.1016/j.cell.2016.09.009}, author = {Jovanic, Tihana and Schneider-Mizell, Casey M and Shao, Mei and Masson, Jean-Baptiste and Denisov, Gennady and Fetter, Richard D and Mensh, Brett D and Truman, James W and Cardona, Albert and Zlatic, Marta} } @article {6282, title = {Cbl-associated protein regulates assembly and function of two tension-sensing structures in Drosophila.}, journal = {Development}, volume = {140}, year = {2013}, month = {2013 Feb 1}, pages = {627-38}, abstract = {

Cbl-associated protein (CAP) localizes to focal adhesions and associates with numerous cytoskeletal proteins; however, its physiological roles remain unknown. Here, we demonstrate that Drosophila CAP regulates the organization of two actin-rich structures in Drosophila: muscle attachment sites (MASs), which connect somatic muscles to the body wall; and scolopale cells, which form an integral component of the fly chordotonal organs and mediate mechanosensation. Drosophila CAP mutants exhibit aberrant junctional invaginations and perturbation of the cytoskeletal organization at the MAS. CAP depletion also results in collapse of scolopale cells within chordotonal organs, leading to deficits in larval vibration sensation and adult hearing. We investigate the roles of different CAP protein domains in its recruitment to, and function at, various muscle subcellular compartments. Depletion of the CAP-interacting protein Vinculin results in a marked reduction in CAP levels at MASs, and vinculin mutants partially phenocopy Drosophila CAP mutants. These results show that CAP regulates junctional membrane and cytoskeletal organization at the membrane-cytoskeletal interface of stretch-sensitive structures, and they implicate integrin signaling through a CAP/Vinculin protein complex in stretch-sensitive organ assembly and function.

}, keywords = {Actin Cytoskeleton, Amino Acid, Amino Acid Sequence, Animal Structures, Animals, Binding Sites, Cell Membrane, Cell-Matrix Junctions, Cellular, Cytoskeletal Proteins, Developmental, Drosophila, Electron, Electrophysiological Phenomena, Gene Expression Regulation, Genome, Hearing Disorders, Insect, Integrins, Larva, Mechanotransduction, Microscopy, Multiprotein Complexes, Muscles, Protein Interaction Mapping, Sequence Homology, Signal Transduction, src Homology Domains, Talin, Transmission, Vibration, Vinculin}, issn = {1477-9129}, doi = {10.1242/dev.085100}, author = {Bharadwaj, Rajnish and Roy, Madhuparna and Ohyama, Tomoko and Sivan-Loukianova, Elena and Delannoy, Michael and Lloyd, Thomas E and Zlatic, Marta and Eberl, Daniel F and Kolodkin, Alex L} } @article {2755, title = {A combinatorial semaphorin code instructs the initial steps of sensory circuit assembly in the Drosophila CNS.}, journal = {Neuron}, volume = {70}, year = {2011}, month = {2011 Apr 28}, pages = {281-98}, abstract = {

Longitudinal axon fascicles within the Drosophila embryonic CNS provide connections between body segments and are required for coordinated neural signaling along the anterior-posterior axis. We show here that establishment of select CNS longitudinal tracts and formation of precise mechanosensory afferent innervation to the same CNS region are coordinately regulated by the secreted semaphorins Sema-2a and Sema-2b. Both Sema-2a and Sema-2b utilize the same neuronal receptor, plexin B (PlexB), but serve distinct guidance functions. Localized Sema-2b attraction promotes the initial assembly of a subset of CNS longitudinal projections and subsequent targeting of chordotonal sensory afferent axons to these same longitudinal connectives, whereas broader Sema-2a repulsion serves to prevent aberrant innervation. In the absence of Sema-2b or PlexB, chordotonal afferent connectivity within the CNS is severely disrupted, resulting in specific larval behavioral deficits. These results reveal that distinct semaphorin-mediated guidance functions converge at PlexB and are critical for functional neural circuit assembly.

}, issn = {1097-4199}, doi = {10.1016/j.neuron.2011.02.050}, author = {Wu, Zhuhao and Sweeney, Lora B and Ayoob, Joseph C and Chak, Kayam and Andreone, Benjamin J and Ohyama, Tomoko and Kerr, Rex and Luo, Liqun and Zlatic, Marta and Kolodkin, Alex L} }