A multilayer circuit architecture for the generation of distinct locomotor behaviors in < i > Drosophila < /i >
Animals generate diverse motor behaviors, yet how the same motor neurons (MNs) generate two distinct or antagonistic behaviors remains an open question. Here we characterizeDrosophila larval muscle activity patterns and premotor/motor circuits to understand how they generate forward and backward locomotion. We show that all body wall MNs are activated during both behaviors, but a subset of MNs change recruitment timing for each behavior. We used TEM to reconstruct a full segment of all 60 MNs and 236 premotor neurons (PMNs), including differentially-recruited MNs. Analysis of this comprehensive connectome identified PMN-MN...
Source: eLife - December 23, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

Sensing of nutrients by CPT1C regulates late endosome/lysosome anterograde transport and axon growth
Anterograde transport of late endosomes or lysosomes (LE/Lys) is crucial for proper axon growth. However, the role of energetic nutrients has been poorly explored. Malonyl-CoA is a precursor of fatty acids, and its intracellular levels highly fluctuate depending on glucose availability or the energy sensor AMP-activated protein kinase (AMPK). We demonstrate in HeLa cells that carnitine palmitoyltransferase 1C (CPT1C) senses malonyl-CoA and enhances LE/Lys anterograde transport by interacting with the endoplasmic reticulum protein protrudin and facilitating the transfer of Kinesin-1 from protrudin to LE/Lys. In cultured mou...
Source: eLife - December 23, 2019 Category: Biomedical Science Tags: Cell Biology Neuroscience Source Type: research

Pathway-, layer- and cell-type-specific thalamic input to mouse barrel cortex
Mouse primary somatosensory barrel cortex (wS1) processes whisker sensory information, receiving input from two distinct thalamic nuclei. The first-order ventral posterior medial (VPM) somatosensory thalamic nucleus most densely innervates layer 4 (L4) barrels, whereas the higher-order posterior thalamic nucleus (medial part, POm) most densely innervates L1 and L5A. We optogenetically stimulated VPM or POm axons, and recorded evoked excitatory postsynaptic potentials (EPSPs) in different cell-types across cortical layers in wS1. We found that excitatory neurons and parvalbumin-expressing inhibitory neurons received the lar...
Source: eLife - December 20, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

FMRP has a cell-type-specific role in CA1 pyramidal neurons to regulate autism-related transcripts and circadian memory
Loss of the RNA binding protein FMRP causes Fragile X Syndrome (FXS), the most common cause of inherited intellectual disability, yet it is unknown how FMRP function varies across brain regions and cell types and how this contributes to disease pathophysiology. Here we use conditional tagging of FMRP and CLIP (FMRP cTag CLIP) to examine FMRP mRNA targets in hippocampal CA1 pyramidal neurons, a critical cell type for learning and memory relevant to FXS phenotypes. Integrating these data with analysis of ribosome-bound transcripts in these neurons revealed CA1-enriched binding of autism-relevant mRNAs, and CA1-specific regul...
Source: eLife - December 20, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

Single-molecule turnover dynamics of actin and membrane coat proteins in clathrin-mediated endocytosis
Actin dynamics generate forces to deform the membrane and overcome the cell's high turgor pressure during clathrin-mediated endocytosis (CME) in yeast, but precise molecular details are still unresolved. Our previous models predicted that actin filaments of the endocytic meshwork continually polymerize and disassemble, turning over multiple times during an endocytic event, similar to other actin systems. We applied single-molecule speckle tracking in live fission yeast to directly measure molecular turnover within CME sites for the first time. In contrast with the overall ~20-sec lifetimes of actin and actin-associated pro...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Cell Biology Physics of Living Systems Source Type: research

Large-scale state-dependent membrane remodeling by a transporter protein
That channels and transporters can influence the membrane morphology is increasingly recognized. Less appreciated is that the extent and free-energy cost of these deformations likely varies among different functional states of a protein, and thus, that they might contribute significantly to defining its mechanism. We consider the trimeric Na+-aspartate symporter GltPh, a homolog of an important class of neurotransmitter transporters, whose mechanism entails one of the most drastic structural changes known. Molecular simulations indicate that when the protomers become inward-facing, they cause deep, long-ranged, and yet mut...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

TLE3 loss confers AR inhibitor resistance by facilitating GR-mediated human prostate cancer cell growth
Androgen receptor (AR) inhibitors represent the mainstay of prostate cancer treatment. In a genome-wide CRISPR-Cas9 screen using LNCaP prostate cancer cells, loss of co-repressorTLE3 conferred resistance to AR antagonists apalutamide and enzalutamide. Genes differentially expressed uponTLE3loss share AR as the top transcriptional regulator, andTLE3 loss rescued the expression of a subset of androgen-responsive genes upon enzalutamide treatment. GR expression was strongly upregulated upon AR inhibition in aTLE3-negative background. This was consistent with binding of TLE3 and AR at theGR locus. Furthermore, GR binding was o...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Cancer Biology Source Type: research

The Fml1-MHF complex suppresses inter-fork strand annealing in fission yeast
Previously we reported that a process called inter-fork strand annealing (IFSA) causes genomic deletions during the termination of DNA replication when an active replication fork converges on a collapsed fork (Morrow et al., 2017). We also identified the FANCM-related DNA helicase Fml1 as a potential suppressor of IFSA. Here, we confirm that Fml1 does indeed suppress IFSA, and show that this function depends on its catalytic activity and ability to interact with Mhf1-Mhf2 via its C-terminal domain. Finally, a plausible mechanism of IFSA suppression is demonstrated by the finding that Fml1 can catalyse regressed fork restor...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Chromosomes and Gene Expression Source Type: research

Common activation mechanism of class A GPCRs
Class A G protein-coupled receptors (GPCRs) influence virtually every aspect of human physiology. Understanding receptor activation mechanism is critical for discovering novel therapeutics since about one-third of all marketed drugs target members of this family. GPCR activation is an allosteric process that couples agonist binding to G protein recruitment, with the hallmark outward movement of transmembrane helix 6 (TM6). However, what leads to TM6 movement and the key residue level changes of this movement remain less well understood. Here, we report a framework to quantify conformational changes. By analyzing the confor...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Computational and Systems Biology Structural Biology and Molecular Biophysics Source Type: research

GC content shapes mRNA storage and decay in human cells
In this study, we combined our recent P-body transcriptome with transcriptomes obtained following silencing of broadly acting mRNA decay and repression factors, and with available CLIP and related data. This revealed the central role of GC content in mRNA fate, in terms of P-body localization, mRNA translation and mRNA stability: P-bodies contain mostly AU-rich mRNAs, which have a particular codon usage associated with a low protein yield; AU-rich and GC-rich transcripts tend to follow distinct decay pathways; and the targets of sequence-specific RBPs and miRNAs are also biased in terms of GC content. Altogether, these res...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Chromosomes and Gene Expression Source Type: research

Length-dependent disassembly maintains four different flagellar lengths in < i > Giardia < /i >
With eight flagella of four different lengths, the parasitic protistGiardia is an ideal model to evaluate flagellar assembly and length regulation. To determine how four different flagellar lengths are maintained, we used live-cell quantitative imaging and mathematical modeling of conserved components of intraflagellar transport (IFT)-mediated assembly and kinesin-13-mediated disassembly in different flagellar pairs. Each axoneme has a long cytoplasmic region extending from the basal body, and transitions to a canonical membrane-bound flagellum at the 'flagellar pore'. We determined that each flagellar pore is the site of ...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Cell Biology Microbiology and Infectious Disease Source Type: research

Uncovering the functional anatomy of the human insula during speech
The contribution of insular cortex to speech production remains unclear and controversial given diverse findings from functional neuroimaging and lesional data. To create a precise spatiotemporal map of insular activity, we performed a series of experiments: single-word articulations of varying complexity, non-speech orofacial movements and speech listening, in a cohort of 27 patients implanted with penetrating intracranial electrodes. The posterior insula was robustly active bilaterally, but after the onset of articulation, during listening to speech and during production of non-speech mouth movements. Preceding articulat...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

De novo design of a homo-trimeric amantadine-binding protein
The computational design of a symmetric protein homo-oligomer that binds a symmetry-matched small molecule larger than a metal ion has not yet been achieved. We used de novo protein design to create a homo-trimeric protein that binds the C3 symmetric small molecule drug amantadine with each protein monomer making identical interactions with each face of the small molecule. Solution NMR data show that the protein has regular three-fold symmetry and undergoes localized structural changes upon ligand binding. A high-resolution X-ray structure reveals a close overall match to the design model with the exception of water molecu...
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

Too hip for two sacral vertebrae
A complex pelvic morphology has been discovered in the fossils of one of the largest crocodylians. (Source: eLife)
Source: eLife - December 19, 2019 Category: Biomedical Science Tags: Evolutionary Biology Source Type: research

Inferring synaptic inputs from spikes with a conductance-based neural encoding model
Descriptive statistical models of neural responses generally aim to characterize the mapping from stimuli to spike responses while ignoring biophysical details of the encoding process. Here, we introduce an alternative approach, the conductance-based encoding model (CBEM), which describes amapping fromstimuli to excitatory and inhibitory synaptic conductances governing the dynamics of sub-threshold membrane potential. Remarkably, we show that the CBEM can be fit to extracellular spike train data and then used to predict excitatory and inhibitory synaptic currents. We validate these predictions with intracellular recordings...
Source: eLife - December 18, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

Catecholaminergic modulation of meta-learning
The remarkable expedience of human learning is thought to be underpinned by meta-learning, whereby slow accumulative learning processes are rapidly adjusted to the current learning environment. To date, the neurobiological implementation of meta-learning remains unclear. A burgeoning literature argues for an important role for the catecholamines dopamine and noradrenaline in meta-learning. Here we tested the hypothesis that enhancing catecholamine function modulates the ability to optimise a meta-learning parameter (learning rate) as a function of environmental volatility. 102 participants completed a task which required l...
Source: eLife - December 18, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

HIV restriction factor APOBEC3G binds in multiple steps and conformations to search and deaminate single-stranded DNA
APOBEC3G (A3G), an enzyme expressed in primates with the potential to inhibit human immunode ficiency virus type 1 (HIV-1) infectivity, is a single-stranded DNA (ssDNA) deoxycytidine deaminase with two domains, a catalytically active, weakly ssDNA binding C-terminal domain (CTD) and a catalytically inactive, strongly ssDNA binding N-terminal domain (NTD). Using optical tweezers, we measure A3G binding a single, long ssDNA substrate under various applied forces to characterize the binding interaction. A3G binds ssDNA in multiple steps and in two distinct conformations, distinguished by degree of ssDNA contraction. A3G stab...
Source: eLife - December 18, 2019 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

The follicle epithelium in the ​ < i > Drosophila ​ < /i > ovary is maintained by a small number of stem cells
The follicle stem cells (FSCs) in the Drosophila ovary are an important experimental model for the study of epithelial stem cell biology. Although decades of research support the conclusion that there are two FSCs per ovariole, a recent study used a novel clonal marking system to conclude that there are 15-16 FSCs per ovariole. We performed clonal analysis using both this novel clonal marking system and standard clonal marking systems, and identified several problems that may have contributed to the overestimate of FSC number. In addition, we developed new methods for accurately measuring clone size, and found that FSC clo...
Source: eLife - December 18, 2019 Category: Biomedical Science Tags: Stem Cells and Regenerative Medicine Source Type: research

Crl activates transcription by stabilizing active conformation of the master stress transcription initiation factor
In this study, we determined a 3.80 Å cryo-EM structure of anEscherichia coli transcription activation complex (E. coli Crl-TAC) comprisingE. coliσS-RNA polymerase ( σS-RNAP) holoenzyme, Crl, and a nucleic-acid scaffold. The structure reveals that Crl interacts with domain 2 of σS ( σS2) and the RNAP core enzyme, but does not contact promoter DNA. Results from subsequent hydrogen-deuterium exchange mass spectrometry (HDX-MS) indicate that Crl stabilizes key structural motifs within σS2 to promote the assembly of the σS-RNAP holoenzyme and also to facilitate formation of an RNA poly...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Chromosomes and Gene Expression Source Type: research

Default mode-visual network hypoconnectivity in an autism subtype with pronounced social visual engagement difficulties
Social visual engagement difficulties are hallmark early signs of autism (ASD) and are easily quantified using eye tracking methods. However, it is unclear how these difficulties are linked to atypical early functional brain organization in ASD. With resting state fMRI data in a large sample of ASD toddlers and other non-ASD comparison groups, we find ASD-related functional hypoconnnectivity between ‘social brain’ circuitry such as the default mode network (DMN) and visual and attention networks. An eye tracking-identified ASD subtype with pronounced early social visual engagement difficulties (GeoPref ASD) is ...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Human Biology and Medicine Neuroscience Source Type: research

Efficient conversion of chemical energy into mechanical work by Hsp70 chaperones
Hsp70 molecular chaperones are abundant ATP-dependent nanomachines that actively reshape non-native, misfolded proteins and assist a wide variety of essential cellular processes. Here we combine complementary theoretical approaches to elucidate the structural and thermodynamic details of the chaperone-induced expansion of a substrate protein, with a particular emphasis on the critical role played by ATP hydrolysis. We first determine the conformational free-energy cost of the substrate expansion due to the binding of multiple chaperones using coarse-grained molecular simulations. We then exploit this result to implement a ...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Physics of Living Systems Source Type: research

Combining genomics and epidemiology to analyse bi-directional transmission of < i > Mycobacterium bovis < /i > in a multi-host system
Quantifying pathogen transmission in multi-host systems is difficult, as exemplified in bovine tuberculosis (bTB) systems, but is crucial for control. The agent of bTB,Mycobacterium bovis, persists in cattle populations worldwide, often where potential wildlife reservoirs exist. However, the relative contribution of different host species to bTB persistence is generally unknown. In Britain, the role of badgers in infection persistence in cattle is highly contentious, despite decades of research and control efforts. We applied Bayesian phylogenetic and machine-learning approaches to bacterial genome data to quantify the rol...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Epidemiology and Global Health Microbiology and Infectious Disease Source Type: research

Rethinking research into metastasis
The partial success of an attempt to repeat findings in cancer biology highlights the need to improve study designs for preclinical research into metastasis and the targeting of cancer cells. (Source: eLife)
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Cancer Biology Source Type: research

Replication Study: Biomechanical remodeling of the microenvironment by stromal caveolin-1 favors tumor invasion and metastasis
As part of theReproducibility Project: Cancer Biology we published a Registered Report (Fiering et al., 2015) that described how we intended to replicate selected experiments from the paper ‘Biomechanical remodeling of the microenvironment by stromal caveolin-1 favors tumor invasion and metastasis’ (Goetz et al., 2011). Here we report the results. Primary mouse embryonic fibroblasts (pMEFs) expressing caveolin 1 (Cav1WT) demonstrated increased extracellular matrix remodelingin vitro compared to Cav1 deficient (Cav1KO) pMEFs, similar to the original study (Goetz et al., 2011).In vivo, we found higher levels of i...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Cancer Biology Source Type: research

Primary cilia deficiency in neural crest cells models Anterior Segment Dysgenesis in mouse
Defects affecting tissues of the anterior segment (AS) of the eye lead to a group of highly debilitating disorders called Anterior Segment Dysgenesis (ASD). Despite the identification of some causative genes, the pathogenesis of ASD remains unclear. Interestingly, several ciliopathies display conditions of the AS. Using conditional targeting ofIft88 withWnt1-Cre, we show that primary cilia of neural crest cells (NCC), precursors of most AS structures, are indispensable for normal AS development and their ablation leads to ASD conditions including abnormal corneal dimensions, defective iridocorneal angle, reduced anterior c...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Developmental Biology Source Type: research

< i > Har-P < /i > , a short < i > P < /i > -element variant, weaponizes < i > P < /i > -transposase to severely impair < i > Drosophila < /i > development
Without transposon-silencing Piwi-interacting RNAs (piRNAs), transposition causes an ovarian atrophy syndrome inDrosophila called gonadal dysgenesis (GD).Harwich (Har) strains withP-elements cause severe GD in F1 daughters whenHar fathers mate with mothers lackingP-element-piRNAs (i.e.ISO1 strain). To address the mystery of whyHar induces severe GD, we bred hybridDrosophila withHar genomic fragments into theISO1 background to createHISR-D or HISR-N lines that still causeDysgenesis or areNon-dysgenic, respectively. In these lines, we discovered a highly truncatedP-element variant we named ‘Har-P’ as the most fre...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Chromosomes and Gene Expression Genetics and Genomics Source Type: research

Compensatory sequence variation between < i > trans < /i > -species small RNAs and their target sites
Trans-species small regulatory RNAs (sRNAs) are delivered to host plants from diverse pathogens and parasites and can target host mRNAs. Howtrans-species sRNAs can be effective on diverse hosts has been unclear. Multiple species of the parasitic plantCuscuta producetrans-species sRNAs that collectively target many host mRNAs. Confirmed target sites are nearly always in highly conserved, protein-coding regions of host mRNAs.Cuscuta trans-species sRNAs can be grouped into superfamilies that have variation in a three-nucleotide period. These variants compensate for synonymous-site variation in host mRNAs. By targeting host mR...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Plant Biology Source Type: research

Antagonism between parasites within snail hosts impacts the transmission of human schistosomiasis
We examined the impact of multiple host and parasite species on transmission of the human parasiteSchistosoma mansoni in Kenya. We showS. mansoni is impacted by cattle and wild vertebrates because of their role in supporting trematode parasites, the larvae of which have antagonistic interactions withS. mansoni in their sharedBiomphalaria vector snails. We discovered the abundant cattle trematode,Calicophoron sukari, fails to develop inBiomphalaria pfeifferi unlessS. mansoni larvae are present in the same snail. Further development ofS. mansoni is subsequently prevented byC. sukari’s presence. Modeling indicated that ...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Ecology Epidemiology and Global Health Source Type: research

Cell-based HTS identifies a chemical chaperone for preventing ER protein aggregation and proteotoxicity
The endoplasmic reticulum (ER) is responsible for folding secretory and membrane proteins, but disturbed ER proteostasis may lead to protein aggregation and subsequent cellular and clinical pathologies. Chemical chaperones have recently emerged as a potential therapeutic approach for ER stress-related diseases. Here, we identified 2-phenylimidazo[2,1-b]benzothiazole derivatives (IBTs) as chemical chaperones in a cell-based high-throughput screen. Biochemical and chemical biology approaches revealed that IBT21 directly binds to unfolded or misfolded proteins and inhibits protein aggregation. Finally, IBT21 prevented cell de...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Cell Biology Source Type: research

Invariant representations of mass in the human brain
An intuitive understanding of physical objects and events is critical for successfully interacting with the world. Does the brain achieve this understanding by running simulations in a mental physics engine, which represents variables such as force and mass, or by analyzing patterns of motion without encoding underlying physical quantities? To investigate, we scanned participants with fMRI while they viewed videos of objects interacting in scenarios indicating their mass. Decoding analyses in brain regions previously implicated in intuitive physical inference revealed mass representations that generalized across variations...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

Single-cell modeling of routine clinical blood tests reveals transient dynamics of human response to blood loss
We present an approach for modeling the unsteady-state population dynamics of the human response to controlled blood loss using these clinical measurements of single-red blood cell (RBC) volume and hemoglobin. We find that the response entails (1) increased production of new RBCs earlier than is currently detectable clinically and (2) a previously unrecognized decreased RBC turnover. Both component responses offset the loss of blood. The model provides a personalized dimensionless ratio that quantifies the balance between increased production and delayed clearance for each individual and may enable earlier detection of bot...
Source: eLife - December 17, 2019 Category: Biomedical Science Tags: Computational and Systems Biology Human Biology and Medicine Source Type: research

Navigating the garden of forking paths for data exclusions in fear conditioning research
In this report, we illustrate the considerable impact of researcher degrees of freedom with respect to exclusion of participants in paradimgs with a learning element. We illustrate this empirically through case examples from human fear conditioning research where the exclusion of 'non-learners' and 'non-responders' is common - despite a lack of consensus on how to define these groups. We illustrate the substantial heterogeneity in exclusion criteria based on a systematic literature search and highlight potential problems and pitfalls of different definitions through case examples based on re-analyses of existing data sets....
Source: eLife - December 16, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

PCK1 and DHODH drive colorectal cancer liver metastatic colonization and hypoxic growth by promoting nucleotide synthesis
Colorectal cancer (CRC) is a major cause of human death. Mortality is primarily due to metastatic organ colonization, with the liver being the primary organ affected. We modeled metastatic CRC (mCRC) liver colonization using patient-derived primary and metastatic tumor xenografts (PDX). Such PDX modeling predicted patient survival outcomes.In vivo selection of multiple PDXs for enhanced metastatic colonization capacity upregulated the gluconeogenic enzyme PCK1, which enhanced liver metastatic hypoxic growth by driving pyrimidine nucleotide biosynthesis under hypoxia. Consistently, highly metastatic tumors upregulated multi...
Source: eLife - December 16, 2019 Category: Biomedical Science Tags: Cancer Biology Human Biology and Medicine Source Type: research

Opioids modulate an emergent rhythmogenic process to depress breathing
How mammalian neural circuits generate rhythmic activity in motor behaviors, such as breathing, walking, and chewing, remains elusive. For breathing, rhythm generation is localized to a brainstem nucleus, the preB ötzinger Complex (preBötC). Rhythmic preBötC population activity consists of strong inspiratory bursts, which drive motoneuronal activity, and weaker burstlets, which we hypothesize reflects an emergent rhythmogenic process. If burstlets underlie inspiratory rhythmogenesis, respiratory depressant s, such as opioids, should reduce burstlet frequency. Indeed, in medullary slices from neonatal mice, t...
Source: eLife - December 16, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

Tritrophic metabolism of plant chemical defenses and its effects on herbivore and predator performance
Insect herbivores are frequently reported to metabolize plant defense compounds, but the physiological and ecological consequences are not fully understood. It has rarely been studied whether such metabolism is genuinely beneficial to the insect, and whether there are any effects on higher trophic levels. Here, we manipulated the detoxification of plant defenses in the herbivorous pest diamondback moth (Plutella xylostella) to evaluate changes in fitness, and additionally examined the effects on a predatory lacewing (Chrysoperla carnea). Silencing glucosinolate sulfatase genes resulted in the systemic accumulation of toxic...
Source: eLife - December 16, 2019 Category: Biomedical Science Tags: Ecology Source Type: research

Ribosome biogenesis restricts innate immune responses to virus infection and DNA
Ribosomes are universally important in biology and their production is dysregulated by developmental disorders, cancer, and virus infection. Although presumed required for protein synthesis, how ribosome biogenesis impacts virus reproduction and cell-intrinsic immune responses remains untested. Surprisingly, we find that restricting ribosome biogenesis stimulated human cytomegalovirus (HCMV) replication without suppressing translation. Interfering with ribosomal RNA (rRNA) accumulation triggered nucleolar stress and repressed expression of 1,392 genes, including High Mobility Group Box 2 (HMGB2), a chromatin-associated pro...
Source: eLife - December 16, 2019 Category: Biomedical Science Tags: Immunology and Inflammation Source Type: research

Tissue-specific shaping of the TCR repertoire and antigen specificity of iNKT cells
Tissue homeostasis is critically dependent on the function of tissue-resident lymphocytes, including lipid-reactive invariant natural killer T (iNKT) cells. Yet, if and how the tissue environment shapes the antigen specificity of iNKT cells remains unknown. By analysing iNKT cells from lymphoid tissues of mice and humans we demonstrate that their T cell receptor (TCR) repertoire is highly diverse and is distinct for cells from various tissues resulting in differential lipid-antigen recognition. Within peripheral tissues iNKT cell recent thymic emigrants exhibit a different TCR repertoire than mature cells, suggesting that ...
Source: eLife - December 16, 2019 Category: Biomedical Science Tags: Immunology and Inflammation Source Type: research

< i > E. coli < /i > TraR allosterically regulates transcription initiation by altering RNA polymerase conformation
TraR and its homolog DksA are bacterial proteins that regulate transcription initiation by binding directly to RNA polymerase (RNAP) rather than to promoter DNA. Effects of TraR mimic the combined effects of DksA and its cofactor ppGpp, but the structural basis for regulation by these factors remains unclear. Here, we use cryo-electron microscopy to determine structures ofEscherichia coli RNAP, with or without TraR, and of an RNAP-promoter complex. TraR binding induced RNAP conformational changes not seen in previous crystallographic analyses, and a quantitative analysis revealed TraR-induced changes in RNAP conformational...
Source: eLife - December 16, 2019 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Structural Biology and Molecular Biophysics Source Type: research

Axon-like protrusions promote small cell lung cancer migration and metastasis
Metastasis is the main cause of death in cancer patients but remains a poorly understood process. Small cell lung cancer (SCLC) is one of the most lethal and most metastatic cancer types. SCLC cells normally express neuroendocrine and neuronal gene programs but accumulating evidence indicates that these cancer cells become relatively more neuronal and less neuroendocrine as they gain the ability to metastasize. Here we show that mouse and human SCLC cells in culture andin vivo can grow cellular protrusions that resemble axons. The formation of these protrusions is controlled by multiple neuronal factors implicated in axono...
Source: eLife - December 13, 2019 Category: Biomedical Science Tags: Cancer Biology Cell Biology Source Type: research

Telophase correction refines division orientation in stratified epithelia
During organogenesis, precise control of spindle orientation balances proliferation and differentiation. In the developing murine epidermis, planar and perpendicular divisions yield symmetric and asymmetric fate outcomes, respectively. Classically, division axis specification involves centrosome migration and spindle rotation, events occurring early in mitosis. Here, we identify a novel orientation mechanism which corrects erroneous anaphase orientations during telophase. The directionality of reorientation correlates with the maintenance or loss of basal contact by the apical daughter. While the scaffolding protein LGN is...
Source: eLife - December 13, 2019 Category: Biomedical Science Tags: Cell Biology Developmental Biology Source Type: research

Uncovering the secret life of Rho GTPases
New methods to directly visualize Rho GTPases reveal how a protein called RhoGDI regulates the activity of these 'molecular switches' at the plasma membrane. (Source: eLife)
Source: eLife - December 13, 2019 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Cell Biology Source Type: research

Direct comparison of clathrin-mediated endocytosis in budding and fission yeast reveals conserved and evolvable features
Conserved proteins drive clathrin-mediated endocytosis (CME), which from yeast to humans involves a burst of actin assembly. To gain mechanistic insights into this process, we performed a side-by-side quantitative comparison of CME in two distantly related yeast species. Though endocytic protein abundance inS. pombe andS. cerevisiae is more similar than previously thought, membrane invagination speed and depth are two-fold greater in fission yeast. In both yeasts, accumulation of ~70 WASp molecules activates the Arp2/3 complex to drive membrane invagination. In contrast to budding yeast, WASp-mediated actin nucleation play...
Source: eLife - December 12, 2019 Category: Biomedical Science Tags: Cell Biology Source Type: research

Single cell transcriptional signatures of the human placenta in term and preterm parturition
More than 135 million births occur each year; yet, the molecular underpinnings of human parturition in gestational tissues, and in particular the placenta, are still poorly understood. The placenta is a complex heterogeneous organ including cells of both maternal and fetal origin, and insults that disrupt the maternal-fetal dialogue could result in adverse pregnancy outcomes such as preterm birth. There is limited knowledge of the cell type composition and transcriptional activity of the placenta and its compartments during physiologic and pathologic parturition. To fill this knowledge gap, we used scRNA-seq to profile the...
Source: eLife - December 12, 2019 Category: Biomedical Science Tags: Genetics and Genomics Human Biology and Medicine Source Type: research

Essential role for InSyn1 in dystroglycan complex integrity and cognitive behaviors in mice
Human mutations in the dystroglycan complex (DGC) result in not only muscular dystrophy but also cognitive impairments. However, the molecular architecture critical for the synaptic organization of the DGC in neurons remains elusive. Here we report Inhibitory Synaptic protein 1 (InSyn1) is a critical component of the DGC whose loss alters the composition of the GABAergic synapses, excitatory/inhibitory balancein vitro andin vivo, and cognitive behavior. Association of InSyn1 with DGC subunits is required for InSyn1 synaptic localization. InSyn1 null neurons also show a significant reduction in DGC and GABA receptor distrib...
Source: eLife - December 12, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

Magnetic resonance measurements of cellular and sub-cellular membrane structures in live and fixed neural tissue
We develop magnetic resonance (MR) methods for real-time measurement of tissue microstructure and membrane permeability of live and fixed excised neonatal mouse spinal cords. Diffusion and exchange MR measurements are performed using the strong static gradient produced by a single-sided permanent magnet. Using tissue delipidation methods, we show that water diffusion is restricted solely by lipid membranes. Most of the diffusion signal can be assigned to water in tissue which is far from membranes. The remaining 25% can be assigned to water restricted on length scales of roughly a micron or less, near or within membrane st...
Source: eLife - December 12, 2019 Category: Biomedical Science Tags: Cell Biology Source Type: research

Developmentally regulated < i > Tcf7l2 < /i > splice variants mediate transcriptional repressor functions during eye formation
Tcf7l2 mediates Wnt/ β-Catenin signalling during development and is implicated in cancer and type-2 diabetes. The mechanisms by which Tcf7l2 and Wnt/β-Catenin signalling elicit such a diversity of biological outcomes are poorly understood. Here, we study the function of zebrafishtcf7l2alternative splice variants and show that only variants that include exon five or an analogous humantcf7l2 variant can effectively provide compensatory repressor function to restore eye formation in embryos lackingtcf7l1a/tcf7l1b function. Knockdown of exon five specifictcf7l2 variants intcf7l1a mutants also compromises eye formatio...
Source: eLife - December 12, 2019 Category: Biomedical Science Tags: Developmental Biology Source Type: research

< i > Straightjacket/ α2δ3 < /i > deregulation is associated with cardiac conduction defects in myotonic dystrophy type 1
Cardiac conduction defects decrease life expectancy in myotonic dystrophy type 1 (DM1), a CTG repeat disorder involving misbalance between two RNA binding factors, MBNL1 and CELF1. However, how DM1 condition translates into conduction disorders remains poorly understood. Here we simulated MBNL1 and CELF1 misbalance in theDrosophila heart and performed TU-tagging-based RNAseq of cardiac cells. We detected deregulations of several genes controlling cellular calcium levels, including increased expression of straightjacket/ α2δ3, which encodes a regulatory subunit of a voltage-gated calcium channel. Straightjacket ...
Source: eLife - December 12, 2019 Category: Biomedical Science Tags: Human Biology and Medicine Source Type: research

The computation of directional selectivity in the < i > Drosophila < /i > OFF motion pathway
In flies, the direction of moving ON and OFF features is computed separately. T4 (ON) and T5 (OFF) are the first neurons in their respective pathways to extract a directionally selective response from their non-selective inputs. Our recent study of T4 found that the integration of offset depolarizing and hyperpolarizing inputs is critical for the generation of directional selectivity. However, T5s lack small-field inhibitory inputs, suggesting they may use a different mechanism. Here we used whole-cell recordings of T5 neurons and found a similar receptive field structure: fast depolarization and persistent, spatially offs...
Source: eLife - December 11, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

The recovery of standing and locomotion after spinal cord injury does not require task-specific training
After complete spinal cord injury, mammals, including mice, rats and cats, recover hindlimb locomotion with treadmill training. The premise is that sensory cues consistent with locomotion reorganize spinal sensorimotor circuits. Here, we show that hindlimb standing and locomotion recover after spinal transection in cats without task-specific training. Spinal-transected cats recovered full weight bearing standing and locomotion after five weeks of rhythmic manual stimulation of triceps surae muscles (non-specific training) and without any intervention. Moreover, cats modulated locomotor speed and performed split-belt locomo...
Source: eLife - December 11, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research

Axon TRAP reveals learning-associated alterations in cortical axonal mRNAs in the lateral amgydala
Local translation can support memory consolidation by supplying new proteins to synapses undergoing plasticity. Translation in adult forebrain dendrites is an established mechanism of synaptic plasticity and is regulated by learning, yet there is no evidence for learning-regulated protein synthesis in adult forebrain axons, which have traditionally been believed to be incapable of translation. Here we show that axons in the adult rat amygdala contain translation machinery, and use translating ribosome affinity purification (TRAP) with RNASeq to identify mRNAs in cortical axons projecting to the amygdala, over 1200 of which...
Source: eLife - December 11, 2019 Category: Biomedical Science Tags: Neuroscience Source Type: research