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2452 Janelia Publications

Showing 91-100 of 2452 results
12/07/23 | Anatomically distributed neural representations of instincts in the hypothalamus.
Stagkourakis S, Spigolon G, Marks M, Feyder M, Kim J, Perona P, Pachitariu M, Anderson DJ
bioRxiv. 2023 Dec 07:. doi: 10.1101/2023.11.21.568163

Artificial activation of anatomically localized, genetically defined hypothalamic neuron populations is known to trigger distinct innate behaviors, suggesting a hypothalamic nucleus-centered organization of behavior control. To assess whether the encoding of behavior is similarly anatomically confined, we performed simultaneous neuron recordings across twenty hypothalamic regions in freely moving animals. Here we show that distinct but anatomically distributed neuron ensembles encode the social and fear behavior classes, primarily through mixed selectivity. While behavior class-encoding ensembles were spatially distributed, individual ensembles exhibited strong localization bias. Encoding models identified that behavior actions, but not motion-related variables, explained a large fraction of hypothalamic neuron activity variance. These results identify unexpected complexity in the hypothalamic encoding of instincts and provide a foundation for understanding the role of distributed neural representations in the expression of behaviors driven by hardwired circuits.

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12/05/23 | Imaging neuronal voltage beyond the scattering limit
Tsai-Wen Chen , Xian-Bin Huang , Sarah E. Plutkis , Katie L. Holland , Luke D. Lavis , Bei-Jung Lin
bioRxiv. 2023 Dec 05:. doi: 10.1101/2023.12.03.568403

Voltage imaging is a promising technique for high-speed recording of neuronal population activity. However, tissue scattering severely limits its application in dense neuronal populations. Here, we adopted the principle of localization microscopy, a technique that enables super-resolution imaging of single-molecules, to resolve dense neuronal activities in vivo. Leveraging the sparse activation of neurons during action potentials (APs), we precisely localize the fluorescence change associated with each AP, creating a super-resolution image of neuronal activities. This approach, termed Activity Localization Imaging (ALI), identifies overlapping neurons and separates their activities with over 10-fold greater precision than what tissue scattering permits. Using ALI, we simultaneously recorded over a hundred densely-labeled CA1 neurons, creating a map of hippocampal theta oscillation at single-cell and single-cycle resolution.

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12/04/23 | Mitochondrial GTP metabolism controls reproductive aging in C. elegans.
Lee Y, Savini M, Chen T, Yang J, Zhao Q, Ding L, Gao SM, Senturk M, Sowa JN, Wang JD, Wang MC
Developmental Cell. 2023 Dec 04;58(23):2718-2731.e7. doi: 10.1016/j.devcel.2023.08.019

Healthy mitochondria are critical for reproduction. During aging, both reproductive fitness and mitochondrial homeostasis decline. Mitochondrial metabolism and dynamics are key factors in supporting mitochondrial homeostasis. However, how they are coupled to control reproductive health remains unclear. We report that mitochondrial GTP (mtGTP) metabolism acts through mitochondrial dynamics factors to regulate reproductive aging. We discovered that germline-only inactivation of GTP- but not ATP-specific succinyl-CoA synthetase (SCS) promotes reproductive longevity in Caenorhabditis elegans. We further identified an age-associated increase in mitochondrial clustering surrounding oocyte nuclei, which is attenuated by GTP-specific SCS inactivation. Germline-only induction of mitochondrial fission factors sufficiently promotes mitochondrial dispersion and reproductive longevity. Moreover, we discovered that bacterial inputs affect mtGTP levels and dynamics factors to modulate reproductive aging. These results demonstrate the significance of mtGTP metabolism in regulating oocyte mitochondrial homeostasis and reproductive longevity and identify mitochondrial fission induction as an effective strategy to improve reproductive health.

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12/01/23 | Structure, interaction, and nervous connectivity of beta cell primary cilia
Andreas Müller , Nikolai Klena , Song Pang , Leticia Elizabeth Galicia Garcia , Davud Sulaymankhil , Oleksandra Topcheva , Monika Seliskar , Hassan Mziaut , Eyke Schöniger , Daniela Friedland , Nicole Kipke , Susanne Kretschmar , Carla Münster , Jürgen Weitz , Marius Distler , Thomas Kurth , Deborah Schmidt , Harald F. Hess , C. Shan Xu , Gaia Pigino , Michele Solimena
bioRxiv. 2023 Dec 01:. doi: 10.1101/2023.12.01.568979

Primary cilia are sensory organelles present in many cell types. Based on an array of microtubules termed axoneme they form a specialized membrane compartment partaking in various signaling processes. Primary cilia of pancreatic islet beta cells play a role in autocrine and paracrine signaling and are linked to diabetes. Yet, the structural basis for their functions is unclear. We present three-dimensional reconstructions of complete mouse and human beta cell cilia, revealing a disorganized 9+0 axoneme structure. Within the islet cilia are spatially confined within deep ciliary pockets or squeezed into narrow extracellular spaces between adjacent cells. Beta and alpha cell cilia physically interact with neighboring islet cells pushing and strongly bending their plasma membranes. Furthermore, beta cells can contain multiple cilia that can meet with other islet cell cilia in the extracellular space. Additionally, beta cell cilia establish connections with islet-projecting nerves. These findings highlight the pivotal role of beta cell primary cilia in islet cell connectivity, pointing at their potential functional role in integrating islet intrinsic and extrinsic signals. These novel insights contribute to understanding their significance in health and diabetes.

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11/30/23 | Connectomic reconstruction predicts the functional organization of visual inputs to the navigation center of the brain.
Garner D, Kind E, Nern A, Houghton L, Zhao A, Sancer G, Rubin GM, Wernet MF, Kim SS
bioRxiv. 2023 Nov 30:. doi: 10.1101/2023.11.29.569241

Many animals, including humans, navigate their surroundings by visual input, yet we understand little about how visual information is transformed and integrated by the navigation system. In , compass neurons in the donut-shaped ellipsoid body of the central complex generate a sense of direction by integrating visual input from ring neurons, a part of the anterior visual pathway (AVP). Here, we densely reconstruct all neurons in the AVP using FlyWire, an AI-assisted tool for analyzing electron-microscopy data. The AVP comprises four neuropils, sequentially linked by three major classes of neurons: MeTu neurons, which connect the medulla in the optic lobe to the small unit of anterior optic tubercle (AOTUsu) in the central brain; TuBu neurons, which connect the anterior optic tubercle to the bulb neuropil; and ring neurons, which connect the bulb to the ellipsoid body. Based on neuronal morphologies, connectivity between different neural classes, and the locations of synapses, we identified non-overlapping channels originating from four types of MeTu neurons, which we further divided into ten subtypes based on the presynaptic connections in medulla and postsynaptic connections in AOTUsu. To gain an objective measure of the natural variation within the pathway, we quantified the differences between anterior visual pathways from both hemispheres and between two electron-microscopy datasets. Furthermore, we infer potential visual features and the visual area from which any given ring neuron receives input by combining the connectivity of the entire AVP, the MeTu neurons' dendritic fields, and presynaptic connectivity in the optic lobes. These results provide a strong foundation for understanding how distinct visual features are extracted and transformed across multiple processing stages to provide critical information for computing the fly's sense of direction.

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11/29/23 | A fluorogenic complementation tool kit for interrogating lipid droplet-organelle interaction
Xiao Li , Rico Gamuyao , Ming-Lun Wu , Woo Jung Cho , Nathan B. Kurtz , Sharon V. King , R.A. Petersen , Daniel R. Stabley , Caleb Lindow , Leslie Climer , Abbas Shirinifard , Francesca Ferrara , Robert E. Throm , Camenzind G. Robinson , Alex Carisey , Alison G. Tebo , Chi-Lun Chang
bioRxiv. 2023 Nov 29:. doi: 10.1101/2023.11.29.569289

Contact sites between lipid droplets and other organelles are essential for cellular lipid and energy homeostasis. Detection of these contact sites at nanometer scale over time in living cells is challenging. Here, we developed a tool kit for detecting contact sites based on Fluorogen- Activated Bimolecular complementation at CONtact sites, FABCON, using a reversible, low affinity split fluorescent protein, splitFAST. FABCON labels contact sites with minimal perturbation to organelle interaction. Via FABCON, we quantitatively demonstrated that endoplasmic reticulum (ER)- and mitochondria (mito)-lipid droplet contact sites are dynamic foci in distinct metabolic conditions, such as during lipid droplet biogenesis and consumption. An automated analysis pipeline further classified individual contact sites into distinct subgroups based on size, likely reflecting differential regulation and function. Moreover, FABCON is generalizable to visualize a repertoire of organelle contact sites including ER-mito. Altogether, FABCON reveals insights into the dynamic regulation of lipid droplet-organelle contact sites and generates new hypotheses for further mechanistical interrogation during metabolic switch.

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11/29/23 | Decoding life's inner workings: advances in quantitative bioimaging.
Henriques R, Leterrier C, Weigel A
Open Biology. 2023 Nov 29;13(11):230329. doi: 10.1098/rsob.230329

This special feature of , titled 'Advances in Quantitative Bioimaging', proposes an overview of the latest advancements in quantitative bioimaging techniques and their wide-ranging applications. The articles cover various topics, including modern imaging methods that enable visualization on a nanoscale, such as super-resolution microscopy and single-particle analysis. These techniques offer unparalleled insights into complex molecular structures and dynamic cellular processes , such as mapping nuclear pore proteins or tracking single histone deposition events throughout the cell cycle. The articles presented in this edition showcase cutting-edge quantitative imaging techniques coupled with advanced computational analysis capable of precisely measuring biological structures and processes. Examples range from correlating calcium release events to underlying protein organization in heart cells to pioneering tools for categorizing changes in microglia morphology under various conditions. This editorial highlights how these advancements are revolutionizing our understanding of living systems, while acknowledging challenges that must be addressed to fully exploit the potential of these emerging technologies, such as improving molecular probes, algorithms and correlation protocols.

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10/28/23 | Imagining the future of optical microscopy: everything, everywhere, all at once.
Balasubramanian H, Hobson CM, Chew T, Aaron JS
Communications Biology. 2023 Oct 28;6(1):1096. doi: 10.1038/s42003-023-05468-9

The optical microscope has revolutionized biology since at least the 17 Century. Since then, it has progressed from a largely observational tool to a powerful bioanalytical platform. However, realizing its full potential to study live specimens is hindered by a daunting array of technical challenges. Here, we delve into the current state of live imaging to explore the barriers that must be overcome and the possibilities that lie ahead. We venture to envision a future where we can visualize and study everything, everywhere, all at once - from the intricate inner workings of a single cell to the dynamic interplay across entire organisms, and a world where scientists could access the necessary microscopy technologies anywhere.

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Darshan LabSvoboda Lab
11/26/23 | Connectivity underlying motor cortex activity during naturalistic goal-directed behavior.
Arseny Finkelstein , Kayvon Daie , Márton Rózsa , Ran Darshan , Karel Svoboda
bioRxiv. 2023 Nov 26:. doi: 10.1101/2023.11.25.568673

Neural representations of information are shaped by local network interactions. Previous studies linking neural coding and cortical connectivity focused on stimulus selectivity in the sensory cortex 14. Here we study neural activity in the motor cortex during naturalistic behavior in which mice gathered rewards with multidirectional tongue reaching. This behavior does not require training and thus allowed us to probe neural coding and connectivity in motor cortex before its activity is shaped by learning a specific task. Neurons typically responded during and after reaching movements and exhibited conjunctive tuning to target location and reward outcome. We used an all-optical 5,4,6,7 method for large-scale causal functional connectivity mapping in vivo. Mapping connectivity between > 20,000,000 excitatory neuronal pairs revealed fine-scale columnar architecture in layer 2/3 of the motor cortex. Neurons displayed local (< 100 µm) like-to-like connectivity according to target-location tuning, and inhibition over longer spatial scales. Connectivity patterns comprised a continuum, with abundant weakly connected neurons and sparse strongly connected neurons that function as network hubs. Hub neurons were weakly tuned to target-location and reward-outcome but strongly influenced neighboring neurons. This network of neurons, encoding location and outcome of movements to different motor goals, may be a general substrate for rapid learning of complex, goal-directed behaviors.

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11/24/23 | Different spectral sensitivities of ON- and OFF-motion pathways enhance the detection of approaching color objects in Drosophila.
Longden KD, Rogers EM, Nern A, Dionne H, Reiser MB
Nature Communications. 2023 Nov 24;14(1):7693. doi: 10.1038/s41467-023-43566-8

Color and motion are used by many species to identify salient objects. They are processed largely independently, but color contributes to motion processing in humans, for example, enabling moving colored objects to be detected when their luminance matches the background. Here, we demonstrate an unexpected, additional contribution of color to motion vision in Drosophila. We show that behavioral ON-motion responses are more sensitive to UV than for OFF-motion, and we identify cellular pathways connecting UV-sensitive R7 photoreceptors to ON and OFF-motion-sensitive T4 and T5 cells, using neurogenetics and calcium imaging. Remarkably, this contribution of color circuitry to motion vision enhances the detection of approaching UV discs, but not green discs with the same chromatic contrast, and we show how this could generalize for systems with ON- and OFF-motion pathways. Our results provide a computational and circuit basis for how color enhances motion vision to favor the detection of saliently colored objects.

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