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192 Publications

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    06/07/22 | Neural circuit pathology driven by Shank3 mutation disrupts social behaviors.
    Kim S, Kim Y, Song I, Ujihara Y, Kim N, Jiang Y, Yin HH, Lee T, Kim IH
    Cell Reports. 2022 Jun 07;39(10):110906. doi: 10.1016/j.celrep.2022.110906

    Dysfunctional sociability is a core symptom in autism spectrum disorder (ASD) that may arise from neural-network dysconnectivity between multiple brain regions. However, pathogenic neural-network mechanisms underlying social dysfunction are largely unknown. Here, we demonstrate that circuit-selective mutation (ctMUT) of ASD-risk Shank3 gene within a unidirectional projection from the prefrontal cortex to the basolateral amygdala alters spine morphology and excitatory-inhibitory balance of the circuit. Shank3 ctMUT mice show reduced sociability as well as elevated neural activity and its amplitude variability, which is consistent with the neuroimaging results from human ASD patients. Moreover, the circuit hyper-activity disrupts the temporal correlation of socially tuned neurons to the events of social interactions. Finally, optogenetic circuit activation in wild-type mice partially recapitulates the reduced sociability of Shank3 ctMUT mice, while circuit inhibition in Shank3 ctMUT mice partially rescues social behavior. Collectively, these results highlight a circuit-level pathogenic mechanism of Shank3 mutation that drives social dysfunction.

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    06/06/22 | Direct Observation of Compartment-Specific Localization and Dynamics of Voltage-Gated Sodium Channels.
    Liu H, Wang H, Pitt GS, Liu ZJ
    Journal of Neuroscience. 2022 Jun 06:. doi: 10.1523/JNEUROSCI.0086-22.2022

    Brain enriched voltage-gated sodium channel (VGSC) Na1.2 and Na1.6 are critical for electrical signaling in the central nervous system. Previous studies have extensively characterized cell-type specific expression and electrophysiological properties of these two VGSCs and how their differences contribute to fine-tuning of neuronal excitability. However, due to lack of reliable labeling and imaging methods, the sub-cellular localization and dynamics of these homologous Na1.2 and Na1.6 channels remain understudied. To overcome this challenge, we combined genome editing, super-resolution and live-cell single molecule imaging to probe subcellular composition, relative abundances and trafficking dynamics of Na1.2 and Na1.6 in cultured mouse and rat neurons and in male and female mouse brain. We discovered a previously uncharacterized trafficking pathway that targets Na1.2 to the distal axon of unmyelinated neurons. This pathway utilizes distinct signals residing in the intracellular loop 1 (ICL1) between transmembrane domain I and II to suppress the retention of Na1.2 in the axon initial segment (AIS) and facilitate its membrane loading at the distal axon. As mouse pyramidal neurons undergo myelination, Na1.2 is gradually excluded from the distal axon as Na1.6 becomes the dominant VGSC in the axon initial segment and nodes of Ranvier. In addition, we revealed exquisite developmental regulation of Na1.2 and Na1.6 localizations in the axon initial segment and dendrites, clarifying the molecular identity of sodium channels in these subcellular compartments. Together, these results unveiled compartment-specific localizations and trafficking mechanisms for VGSCs, which could be regulated separately to modulate membrane excitability in the brain.Direct observation of endogenous voltage-gated sodium channels reveals a previously uncharacterized distal axon targeting mechanism and the molecular identity of sodium channels in distinct subcellular compartments.

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    06/02/22 | Allosteric interactions prime androgen receptor dimerization and activation.
    Wasmuth EV, Broeck AV, LaClair JR, Hoover EA, Lawrence KE, Paknejad N, Pappas K, Matthies D, Wang B, Feng W, Watson PA, Zinder JC, Karthaus WR, de la Cruz MJ, Hite RK, Manova-Todorova K, Yu Z, Weintraub ST, Klinge S, Sawyers CL
    Molecular Cell. 2022 Jun 02;82(11):2021-31. doi: 10.1016/j.molcel.2022.03.035

    The androgen receptor (AR) is a nuclear receptor that governs gene expression programs required for prostate development and male phenotype maintenance. Advanced prostate cancers display AR hyperactivation and transcriptome expansion, in part, through AR amplification and interaction with oncoprotein cofactors. Despite its biological importance, how AR domains and cofactors cooperate to bind DNA has remained elusive. Using single-particle cryo-electron microscopy, we isolated three conformations of AR bound to DNA, showing that AR forms a non-obligate dimer, with the buried dimer interface utilized by ancestral steroid receptors repurposed to facilitate cooperative DNA binding. We identify novel allosteric surfaces which are compromised in androgen insensitivity syndrome and reinforced by AR's oncoprotein cofactor, ERG, and by DNA-binding motifs. Finally, we present evidence that this plastic dimer interface may have been adopted for transactivation at the expense of DNA binding. Our work highlights how fine-tuning AR's cooperative interactions translate to consequences in development and disease.

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    06/02/22 | Targeting LIPA independent of its lipase activity is a therapeutic strategy in solid tumors via induction of endoplasmic reticulum stress.
    Liu X, Viswanadhapalli S, Kumar S, Lee T, Moore A, Ma S, Chen L, Hsieh M, Li M, Sareddy GR, Parra K, Blatt EB, Reese TC, Zhao Y, Chang A, Yan H, Xu Z, Pratap UP, Liu Z, Roggero CM, Tan Z, Weintraub ST, Peng Y, Tekmal RR, Arteaga CL, Lippincott-Schwartz J, Vadlamudi RK, Ahn J, Raj GV
    Nature Cancer. 2022 Jun 02;3(7):866-884. doi: 10.1038/s43018-022-00389-8

    Triple-negative breast cancer (TNBC) has a poor clinical outcome, due to a lack of actionable therapeutic targets. Herein we define lysosomal acid lipase A (LIPA) as a viable molecular target in TNBC and identify a stereospecific small molecule (ERX-41) that binds LIPA. ERX-41 induces endoplasmic reticulum (ER) stress resulting in cell death, and this effect is on target as evidenced by specific LIPA mutations providing resistance. Importantly, we demonstrate that ERX-41 activity is independent of LIPA lipase function but dependent on its ER localization. Mechanistically, ERX-41 binding of LIPA decreases expression of multiple ER-resident proteins involved in protein folding. This targeted vulnerability has a large therapeutic window, with no adverse effects either on normal mammary epithelial cells or in mice. Our study implicates a targeted strategy for solid tumors, including breast, brain, pancreatic and ovarian, whereby small, orally bioavailable molecules targeting LIPA block protein folding, induce ER stress and result in tumor cell death.

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    Sternson Lab
    06/01/22 | Development of an adrenocortical cell model of calcium signaling modulation to decipher the molecular mechanisms responsible for primary aldosteronism
    BakhtaFedlaoui , Teresa Cosentino , Zeina R. Al Sayed , Isabelle Giscos-Douriez , Fabio L. Fernandes-Rosa , Jean-SébastienHulot , Chris Magnus , Scott M. Sternson , Maria Christina Zennaro , Sheerazed Boulkroun
    Archives of Cardiovascular Diseases Supplements. 2022 Jun 01;14(2):160. doi: 10.1016/j.acvdsp.2022.04.153

    Primary aldosteronism (PA) is the most frequent form of secondary hypertension. The identification of germline or somatic mutations in different genes coding for ion channels and defines PA as a channelopathy. These mutations promote activation of calcium signaling, the main trigger for aldosterone biosynthesis.

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    06/01/22 | Quantifying Molecular Dynamics within Complex Cellular Morphologies using LLSM-FRAP.
    Colin-York H, Heddleston J, Wait E, Karedla N, DeSantis M, Khuon S, Chew T, Sbalzarini IF, Fritzsche M
    Small Methods. 2022 Jun 01:e2200149. doi: 10.1002/smtd.202200149

    Quantifying molecular dynamics within the context of complex cellular morphologies is essential toward understanding the inner workings and function of cells. Fluorescence recovery after photobleaching (FRAP) is one of the most broadly applied techniques to measure the reaction diffusion dynamics of molecules in living cells. FRAP measurements typically restrict themselves to single-plane image acquisition within a subcellular-sized region of interest due to the limited temporal resolution and undesirable photobleaching induced by 3D fluorescence confocal or widefield microscopy. Here, an experimental and computational pipeline combining lattice light sheet microscopy, FRAP, and numerical simulations, offering rapid and minimally invasive quantification of molecular dynamics with respect to 3D cell morphology is presented. Having the opportunity to accurately measure and interpret the dynamics of molecules in 3D with respect to cell morphology has the potential to reveal unprecedented insights into the function of living cells.

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    05/31/22 | Mesolimbic dopamine adapts the rate of learning from action.
    Luke T. Coddington , Sarah E. Lindo , Joshua T. Dudman
    bioRxiv. 2022 May 31:. doi: 10.1101/2021.05.31.446464

    Recent success in training artificial agents and robots derives from a combination of direct learning of behavioral policies and indirect learning via value functions. Policy learning and value learning employ distinct algorithms that optimize behavioral performance and reward prediction, respectively. In animals, behavioral learning and the role of mesolimbic dopamine signaling have been extensively evaluated with respect to reward prediction; however, to date there has been little consideration of how direct policy learning might inform our understanding. Here we used a comprehensive dataset of orofacial and body movements to understand how behavioral policies evolve as naive, head-restrained mice learned a trace conditioning paradigm. Individual differences in initial dopaminergic reward responses correlated with the emergence of learned behavioral policy, but not the emergence of putative value encoding for a predictive cue. Likewise, physiologically-calibrated manipulations of mesolimbic dopamine produced multiple effects inconsistent with value learning but predicted by a neural network-based model that used dopamine signals to set an adaptive rate, not an error signal, for behavioral policy learning. This work provides strong evidence that phasic dopamine activity can regulate direct learning of behavioral policies, expanding the explanatory power of reinforcement learning models for animal learning.

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    05/29/22 | Plasticity-induced actin polymerization in the dendritic shaft regulates intracellular AMPA receptor trafficking.
    V. C. Wong , P.R. Houlihan , H. Liu , D. Walpita , M.C. DeSantis , Z. Liu , E. K. O’Shea
    bioRxiv. 2022 May 29:. doi: 10.1101/2022.05.29.493906

    AMPA-type receptors (AMPARs) are rapidly inserted into synapses undergoing long-term potentiation (LTP) to increase synaptic transmission, but how AMPAR-containing vesicles are selectively trafficked to these synapses during LTP is not known. Here we developed a strategy to label AMPAR GluA1 subunits expressed from the endogenous loci of rat hippocampal neurons such that the motion of GluA1-containing vesicles in time-lapse sequences can be characterized using single-particle tracking and mathematical modeling. We find that GluA1-containing vesicles are confined and concentrated near sites of stimulation-induced plasticity. We show that confinement is mediated by actin polymerization, which hinders the active transport of GluA1-containing vesicles along the length of the dendritic shaft by modulating the rheological properties of the cytoplasm. Actin polymerization also facilitates myosin-mediated transport of GluA1-containing vesicles to exocytic sites. We conclude that neurons utilize F-actin to increase vesicular GluA1 reservoirs and promote exocytosis proximal to the sites of neuronal activity.

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    05/28/22 | An essential experimental control for functional connectivity mapping with optogenetics.
    David Tadres , Hiroshi M. Shiozaki , Ibrahim Tastekin , David L. Stern , Matthieu Louis
    bioRxiv. 2022 May 28:. doi: 10.1101/2022.05.26.493610

    To establish functional connectivity between two candidate neurons that might form a circuit element, a common approach is to activate an optogenetic tool such as Chrimson in the candidate pre-synaptic neuron and monitor fluorescence of the calcium-sensitive indicator GCaMP in a candidate post-synaptic neuron. While performing such experiments, we found that low levels of leaky Chrimson expression can lead to strong artifactual GCaMP signals in presumptive postsynaptic neurons even when Chrimson is not intentionally expressed in any particular neurons. Withholding all-trans retinal, the chromophore required as a co-factor for Chrimson response to light, eliminates GCaMP signal but does not provide an experimental control for leaky Chrimson expression. Leaky Chrimson expression appears to be an inherent feature of current Chrimson transgenes, since artifactual connectivity was detected with Chrimson transgenes integrated into three different genomic locations (two insertions tested in larvae; a third insertion tested in the adult fly). These false-positive signals may complicate the interpretation of functional connectivity experiments. We illustrate how a no-Gal4 negative control improves interpretability of functional connectivity assays. We also propose a simple but effective procedure to identify experimental conditions that minimize potentially incorrect interpretations caused by leaky Chrimson expression.

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    05/26/22 | One engram two readouts: stimulus dynamics switch a learned behavior in Drosophila
    Mehrab N Modi , Adithya Rajagopalan , Hervé Rouault , Yoshinori Aso , Glenn C Turner
    bioRxiv. 2022 May 26:. doi: 10.1101/2022.05.24.492551

    Memory guides the choices an animal makes across widely varying conditions in dynamic environments. Consequently, the most adaptive choice depends on the options available. How can a single memory support optimal behavior across different sets of choice options? We address this using olfactory learning in Drosophila. Even when we restrict an odor-punishment association to a single set of synapses using optogenetics, we find that flies still show choice behavior that depends on the options it encounters. Here we show that how the odor choices are presented to the animal influences memory recall itself. Presenting two similar odors in sequence enabled flies to not only discriminate them behaviorally but also at the level of neural activity. However, when the same odors were encountered as solitary stimuli, no such differences were detectable. These results show that memory recall is not simply a comparison to a static learned template, but can be adaptively modulated by stimulus dynamics.

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