Synaptic mechanisms underlying modulation of locomotor-related motoneuron output by premotor cholinergic interneurons
Spinal motor networks are formed by diverse populations of interneurons that set the strength and rhythmicity of behaviors such as locomotion. A small cluster of cholinergic interneurons, expressing the transcription factor Pitx2, modulates the intensity of muscle activation via 'C-bouton' inputs to motoneurons. However, the synaptic mechanisms underlying this neuromodulation remain unclear. Here, we confirm in mice that Pitx2+ interneurons are active during fictive locomotion and that their chemogenetic inhibition reduces the amplitude of motor output. Furthermore, after genetic ablation of cholinergic Pitx2+ interneurons...
Source: eLife - February 21, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Multifaceted secretion of htNSC-derived hypothalamic islets induces survival and antidiabetic effect via peripheral implantation in mice
We report that mouse hypothalamic stem/progenitor cells produce multiple pancreatic, gastrointestinal and hypothalamic peptides in addition to exosomes. Through cell sorting and selection according to insulin promoter activity, we generated a subpopulation of these cells which formed 3D spherical structure with combined features of hypothalamic neurospheres and pancreatic islets. Through testing streptozotocin-induced pancreatic islet disruption and fatal diabetes, we found that peripheral implantation of these spheres in mice led to remarkable improvements in general health and survival in addition to a moderate antidiabe...
Source: eLife - February 21, 2020 Category: Biomedical Science Tags: Stem Cells and Regenerative Medicine Source Type: research

Mechanisms that allow cortical preparatory activity without inappropriate movement
We reveal a novel mechanism that explains how preparatory activity can evolve in motor-related cortical areas without prematurely inducing movement. The smooth eye movement region of the frontal eye fields (FEFSEM) is a critical node in the neural circuit controlling smooth pursuit eye movement. Preparatory activity evolves in the monkey FEFSEM during fixation in parallel with an objective measure of visual-motor gain. We propose that the use of FEFSEM output as a gain signal rather than a movement command allows for preparation to progress in pursuit without causing movement. We also show that preparatory modulation of fi...
Source: eLife - February 21, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Rapid sex-specific adaptation to high temperature in < i > Drosophila < /i >
The pervasive occurrence of sexual dimorphism demonstrates different adaptive strategies of males and females. While different reproductive strategies of the two sexes are well-characterized, very little is known about differential functional requirements of males and females in their natural habitats. Here, we study the impact environmental change on the selection response in both sexes. Exposing replicatedDrosophila populations to a novel temperature regime, we demonstrate sex-specific changes in gene expression, metabolic and behavioral phenotypes in less than 100 generations. This indicates not only different functiona...
Source: eLife - February 21, 2020 Category: Biomedical Science Tags: Evolutionary Biology Genetics and Genomics Source Type: research

Words without meaning
Many of the words used by scientists when reviewing manuscripts, job candidates and grant applications – words such as incremental, novelty, mechanism, descriptive and impact – have lost their meaning. (Source: eLife)
Source: eLife - February 21, 2020 Category: Biomedical Science Source Type: research

Targeted induction of a silent fungal gene cluster encoding the bacteria-specific germination inhibitor fumigermin
Microorganisms produce numerous secondary metabolites (SMs) with various biological activities. Many of their encoding gene clusters are silent under standard laboratory conditions because for their activation they need the ecological context, such as the presence of other microorganisms. The true ecological function of most SMs remains obscure, but understanding of both the activation of silent gene clusters and the ecological function of the produced compounds is of importance to reveal functional interactions in microbiomes. Here, we report the identification of an as-yet uncharacterized silent gene cluster of the fungu...
Source: eLife - February 21, 2020 Category: Biomedical Science Tags: Ecology Microbiology and Infectious Disease Source Type: research

Polypyrimidine tract binding proteins are essential for B cell development
Polypyrimidine Tract Binding Protein 1 (PTBP1) is a RNA-binding protein (RBP) expressed throughout B cell development. Deletion ofPtbp1 in mouse pro-B cells results in upregulation of PTBP2 and normal B cell development. We show that PTBP2 compensates for PTBP1 in B cell ontogeny as deletion of bothPtbp1 andPtbp2 results in a complete block at the pro-B cell stage and a lack of mature B cells. In pro-B cells PTBP1 ensures precise synchronisation of the activity of cyclin dependent kinases at distinct stages of the cell cycle, suppresses S-phase entry and promotes progression into mitosis. PTBP1 controls mRNA abundance and ...
Source: eLife - February 21, 2020 Category: Biomedical Science Tags: Chromosomes and Gene Expression Immunology and Inflammation Source Type: research

Primary and secondary anti-viral response captured by the dynamics and phenotype of individual T cell clones
The diverse repertoire of T-cell receptors (TCR) plays a key role in the adaptive immune response to infections. Using TCR alpha and beta repertoire sequencing for T-cell subsets, as well as single-cell RNAseq and TCRseq, we track the concentrations and phenotypes of individual T-cell clones in response to primary and secondary yellow fever immunization — the model for acute infection in humans — showing their large diversity. We confirm the secondary response is an order of magnitude weaker, albeit ∼ 10 days faster than the primary one. Estimating the fraction of the T-cell response directed against the si...
Source: eLife - February 21, 2020 Category: Biomedical Science Tags: Computational and Systems Biology Immunology and Inflammation Source Type: research

Quantitative properties of a feedback circuit predict frequency-dependent pattern separation
Feedback inhibitory motifs are thought to be important for pattern separation across species. How feedback circuits may implement pattern separation of biologically plausible, temporally structured input in mammals is, however, poorly understood. We have quantitatively determined key properties ofnetfeedback inhibition in the mouse dentate gyrus, a region critically involved in pattern separation. Feedback inhibition is recruited steeply with a low dynamic range (0% to 4% of active GCs), and with a non-uniform spatial profile. Additionally, net feedback inhibition shows frequency-dependent facilitation, driven by strongly ...
Source: eLife - February 20, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

The hippocampus encodes delay and value information during delay-discounting decision making
The hippocampus, a region critical for memory and spatial navigation, has been implicated in delay discounting, the decline in subjective reward value when a delay is imposed. However, how delay information is encoded in the hippocampus is poorly understood. Here we recorded from CA1 of mice performing a delay-discounting decision-making task, where delay lengths, delay positions, and reward amounts were changed across sessions, and identified subpopulations of CA1 neurons which increased or decreased their firing rate during long delays. The activity of both delay-active and -suppressive cells reflected delay length, dela...
Source: eLife - February 20, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

ParB spreading on DNA requires cytidine triphosphate < i > in vitro < /i >
In all living organisms, it is essential to transmit genetic information faithfully to the next generation. The SMC-ParAB-parS system is widely employed for chromosome segregation in bacteria. A DNA-binding protein ParB nucleates onparS sites and must associate with neighboring DNA, a process known as spreading, to enable efficient chromosome segregation. Despite its importance, how the initial few ParB molecules nucleating atparS sites recruit hundreds of further ParB to spread is not fully understood. Here, we reconstitute aparS-dependent ParB spreading event using purified proteins fromCaulobactercrescentus and show tha...
Source: eLife - February 20, 2020 Category: Biomedical Science Tags: Chromosomes and Gene Expression Microbiology and Infectious Disease Source Type: research

The transpeptidase PBP2 governs initial localization and activity of the major cell-wall synthesis machinery in < i > E. coli < /i >
Bacterial shape is physically determined by the peptidoglycan cell wall. The cell-wall-synthesis machinery responsible for rod shape inEscherichia coliis the processive 'Rod complex'. Previously, cytoplasmic MreB filaments were thought to govern formation and localization of Rod complexes based on local cell-envelope curvature. Using single-particle tracking of the transpeptidase and Rod-complex component PBP2, we found that PBP2 binds to a substrate different from MreB. Depletion and localization experiments of other putative Rod-complex components provide evidence that none of those provide the sole rate-limiting substra...
Source: eLife - February 20, 2020 Category: Biomedical Science Tags: Microbiology and Infectious Disease Physics of Living Systems Source Type: research

Rapid regulation of vesicle priming explains synaptic facilitation despite heterogeneous vesicle:Ca < sup > 2+ < /sup > channel distances
Chemical synaptic transmission relies on the Ca2+-induced fusion of transmitter-laden vesicles whose coupling distance to Ca2+-channels determines synaptic release probability and short-term plasticity, the facilitation or depression of repetitive responses. Here, using electron- and super-resolution microscopy at theDrosophila neuromuscular junction we quantitatively map vesicle:Ca2+-channel coupling distances. These are very heterogeneous, resulting in a broad spectrum of vesicular release probabilities within synapses. Stochastic simulations of transmitter release from vesicles placed according to this distribution reve...
Source: eLife - February 20, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Mouse retinal cell behaviour in space and time using light sheet fluorescence microscopy
As the general population ages, more people are affected by eye diseases, such as retinopathies. It is therefore critical to improve imaging of eye disease mouse models. Here, we demonstrate that 1) rapid, quantitative 3D and 4D (time lapse) imaging of cellular and subcellular processes in the mouse eye is feasible, with and without tissue clearing, using light-sheet fluorescent microscopy (LSFM); 2) flat-mounting retinas for confocal microscopy significantly distorts tissue morphology, confirmed by quantitative correlative LSFM-Confocal imaging of vessels; 3) LSFM readily reveals new features of even well-studied eye dise...
Source: eLife - February 19, 2020 Category: Biomedical Science Tags: Cell Biology Developmental Biology Source Type: research

How new genes are born
Analysis of yeast, fly and human genomes suggests that sequence divergence is not the main source of orphan genes. (Source: eLife)
Source: eLife - February 19, 2020 Category: Biomedical Science Tags: Computational and Systems Biology Evolutionary Biology Source Type: research

Tailless/TLX reverts intermediate neural progenitors to stem cells driving tumourigenesis via repression of < i > asense/ASCL1 < /i >
Understanding the sequence of events leading to cancer relies in large part upon identifying the tumour cell of origin. Glioblastoma is the most malignant brain cancer but the early stages of disease progression remain elusive. Neural lineages have been implicated as cells of origin, as have glia. Interestingly, high levels of the neural stem cell regulator TLX correlate with poor patient prognosis. Here we show that high levels of theDrosophila TLX homologue, Tailless, initiate tumourigenesis by reverting intermediate neural progenitors to a stem cell state. Strikingly, we could block tumour formation completely by re-exp...
Source: eLife - February 19, 2020 Category: Biomedical Science Tags: Developmental Biology Stem Cells and Regenerative Medicine Source Type: research

Opioids depress breathing through two small brainstem sites
The rates of opioid overdose in the United States quadrupled between 1999 and 2017, reaching a staggering 130 deaths per day. This health epidemic demands innovative solutions that require uncovering the key brain areas and cell types mediating the cause of overdose — opioid-induced respiratory depression. Here, we identify two primary changes to murine breathing after administering opioids. These changes implicate the brainstem's breathing circuitry which we confirm by locally eliminating the µ-Opioid receptor. We find the critical brain site is the preBöt zinger Complex, where the breathing rhythm origin...
Source: eLife - February 19, 2020 Category: Biomedical Science Tags: Human Biology and Medicine Neuroscience Source Type: research

Presynaptic GABA < sub > B < /sub > receptors functionally uncouple somatostatin interneurons from the active hippocampal network
Information processing in cortical neuronal networks relies on properly balanced excitatory and inhibitory neurotransmission. A ubiquitous motif for maintaining this balance is the somatostatin interneuron (SOM-IN) feedback microcircuit. Here, we investigate the modulation of this microcircuit by presynaptic GABAB receptors (GABABRs) in the rodent hippocampus. Whole-cell recordings from SOM-INs revealed that both excitatory and inhibitory synaptic inputs are strongly inhibited by GABABRs, while optogenetic activation of the interneurons shows that their inhibitory output is also strongly suppressed. Electron microscopic an...
Source: eLife - February 19, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Patterned perturbation of inhibition can reveal the dynamical structure of neural processing
Perturbation of neuronal activity is key to understanding the brain's functional properties, however, intervention studies typically perturb neurons in a nonspecific manner. Recent optogenetics techniques have enabled patterned perturbations, in which specific patterns of activity can be invoked in identified target neurons to reveal more specific cortical function. Here, we argue that patterned perturbation of neurons is in fact necessary to reveal the specific dynamics of inhibitory stabilization, emerging in cortical networks with strong excitatory and inhibitory functional subnetworks, as recently reported in mouse vis...
Source: eLife - February 19, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

< i > Stxbp1/Munc18-1 < /i > haploinsufficiency impairs inhibition and mediates key neurological features of < i > STXBP1 < /i > encephalopathy
Mutations in genes encoding synaptic proteins cause many neurodevelopmental disorders, with the majority affecting postsynaptic apparatuses and much fewer in presynaptic proteins. Syntaxin-binding protein 1 (STXBP1, also known as MUNC18-1) is an essential component of the presynaptic neurotransmitter release machinery.De novo heterozygous pathogenic variants inSTXBP1 are among the most frequent causes of neurodevelopmental disorders including intellectual disabilities and epilepsies. These disorders, collectively referred to asSTXBP1 encephalopathy, encompass a broad spectrum of neurologic and psychiatric features, but the...
Source: eLife - February 19, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

A widely distributed metalloenzyme class enables gut microbial metabolism of host- and diet-derived catechols
Catechol dehydroxylation is a central chemical transformation in the gut microbial metabolism of plant- and host-derived small molecules. However, the molecular basis for this transformation and its distribution among gut microorganisms are poorly understood. Here, we characterize a molybdenum-dependent enzyme from the human gut bacteriumEggerthella lenta that dehydroxylates catecholamine neurotransmitters. Our findings suggest that this activity enablesE. lenta to use dopamine as an electron acceptor. We also identify candidate dehydroxylases that metabolize additional host- and plant-derived catechols. These dehydroxylas...
Source: eLife - February 18, 2020 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Microbiology and Infectious Disease Source Type: research

Genetic analysis of the Arabidopsis TIR1/AFB auxin receptors reveals both overlapping and specialized functions
The TIR1/AFB auxin co-receptors mediate diverse responses to the plant hormone auxin. The Arabidopsis genome encodes six TIR1/AFB proteins representing three of the four clades that were established prior to angiosperm radiation. To determine the role of these proteins in plant development we performed an extensive genetic analysis involving the generation and characterization of all possible multiply-mutant lines. We find that loss of all six TIR1/AFB proteins results in early embryo defects and eventually seed abortion, and yet a single wild-type allele ofTIR1orAFB2 is sufficient to support growth throughout development....
Source: eLife - February 18, 2020 Category: Biomedical Science Tags: Developmental Biology Plant Biology Source Type: research

Social structure learning in human anterior insula
Humans form social coalitions in every society, yet we know little about how we learn and represent social group boundaries. Here we derive predictions from a computational model of latent structure learning to move beyond explicit category labels and interpersonal, or dyadic similarity as the sole inputs to social group representations. Using a model-based analysis of functional neuroimaging data, we find that separate areas correlate with dyadic similarity and latent structure learning. Trial-by-trial estimates of 'allyship' based on dyadic similarity between participants and each agent recruited medial prefrontal cortex...
Source: eLife - February 18, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

< i > Plasmodium < /i > -infected erythrocytes induce secretion of IGFBP7 to form type II rosettes and escape phagocytosis
In malaria, rosetting is described as a phenomenon where an infected erythrocyte (IRBC) is attached to uninfected erythrocytes (URBC). In some studies, rosetting has been associated with malaria pathogenesis. Here, we have identified a new type of rosetting. Using a step-by-step approach, we identified IGFBP7, a protein secreted by monocytes in response to parasite stimulation, as a rosette-stimulator forPlasmodium falciparum- andP. vivax-IRBC. IGFBP7-mediated rosette-stimulation was rapid yet reversible. Unlike type I rosetting that involves direct interaction of rosetting ligands on IRBC and receptors on URBC, The IGFBP7...
Source: eLife - February 18, 2020 Category: Biomedical Science Tags: Immunology and Inflammation Microbiology and Infectious Disease Source Type: research

A Toll-receptor map underlies structural brain plasticity
Experience alters brain structure, but the underlying mechanism remained unknown. Structural plasticity reveals that brain function is encoded in generative changes to cells that compete with destructive processes driving neurodegeneration. At an adult critical period, experience increases fiber number and brain size inDrosophila. Here, we asked if Toll receptors are involved. Tolls demarcate a map of brain anatomical domains. Focusing onToll-2, loss of function caused apoptosis, neurite atrophy and impaired behaviour. Toll-2 gain of function and neuronal activity at the critical period increased cell number. Toll-2 induce...
Source: eLife - February 18, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Synteny-based analyses indicate that sequence divergence is not the main source of orphan genes
The origin of ‘orphan’ genes, species-specific sequences that lack detectable homologues, has remained mysterious since the dawn of the genomic era. There are two dominant explanations for orphan genes: complete sequence divergence from ancestral genes, such that homologues are not readily detectable; and de novo emergence from ancestral non-genic sequences, such that homologues genuinely do not exist. The relative contribution of the two processes remains unknown. Here, we harness the special circumstance of conserved synteny to estimate the contribution of complete divergence to the pool of orphan gen es. By ...
Source: eLife - February 18, 2020 Category: Biomedical Science Tags: Computational and Systems Biology Evolutionary Biology Source Type: research

EDEM2 stably disulfide-bonded to TXNDC11 catalyzes the first mannose trimming step in mammalian glycoprotein ERAD
Sequential mannose trimming of N-glycan (Man9GlcNAc2 -> Man8GlcNAc2 -> Man7GlcNAc2) facilitates endoplasmic reticulum-associated degradation of misfolded glycoproteins (gpERAD). Our gene knockout experiments in human HCT116 cells have revealed that EDEM2 is required for the first step. However, it was previously shown that purified EDEM2 exhibited no a1,2-mannosidase activity toward Man9GlcNAc2 in vitro. Here, we found that EDEM2 was stably disulfide-bonded to TXNDC11, an endoplasmic reticulum protein containing five thioredoxin (Trx)-like domains. C558 present outside of the mannosidase homology domain of EDEM2 was ...
Source: eLife - February 17, 2020 Category: Biomedical Science Tags: Cell Biology Source Type: research

A single-parasite transcriptional atlas of < i > Toxoplasma gondii < /i > reveals novel control of antigen expression
Toxoplasma gondii, a protozoan parasite, undergoes a complex and poorly understood developmental process that is critical for establishing a chronic infection in its intermediate hosts. Here, we applied single-cell RNA-sequencing (scRNA-seq) on>5,400 Toxoplasma in both tachyzoite and bradyzoite stages using three widely studied strains to construct a comprehensive atlas of cell-cycle and asexual development, revealing hidden states and transcriptional factors associated with each developmental stage. Analysis of SAG1-related sequence (SRS) antigenic repertoire reveals a highly heterogeneous, sporadic expression pattern ...
Source: eLife - February 17, 2020 Category: Biomedical Science Tags: Cell Biology Microbiology and Infectious Disease Source Type: research

ESCO1 and CTCF enable formation of long chromatin loops by protecting cohesin < sup > STAG1 < /sup > from WAPL
Eukaryotic genomes are folded into loops. It is thought that these are formed by cohesin complexesvia extrusion, either until loop expansion is arrested by CTCF or until cohesin is removed from DNA by WAPL. Although WAPL limits cohesin's chromatin residence time to minutes, it has been reported that some loops exist for hours. How these loops can persist is unknown. We show that during G1-phase, mammalian cells contain acetylated cohesinSTAG1 which binds chromatin for hours, whereas cohesinSTAG2 binds chromatin for minutes. Our results indicate that CTCF and the acetyltransferase ESCO1 protect a subset of cohesinSTAG1 comp...
Source: eLife - February 17, 2020 Category: Biomedical Science Tags: Cell Biology Chromosomes and Gene Expression Source Type: research

Repression of viral gene expression and replication by the unfolded protein response effector XBP1u
The unfolded protein response (UPR) is a cellular homeostatic circuit regulating protein synthesis and processing in the ER by three ER-to-nucleus signaling pathways. One pathway is triggered by the inositol-requiring enzyme 1 (IRE1), which splices the X-box binding protein 1 (Xbp1) mRNA, thereby enabling expression of XBP1s. Another UPR pathway activates the activating transcription factor 6 (ATF6). Here we show that murine cytomegalovirus (MCMV), a prototypic β-herpesvirus, harnesses the UPR to regulate its own life cycle. MCMV activates the IRE1-XBP1 pathway early post infection to relieve repression by XBP1u, the ...
Source: eLife - February 17, 2020 Category: Biomedical Science Tags: Cell Biology Microbiology and Infectious Disease Source Type: research

Translational initiation in < i > E. coli < /i > occurs at the correct sites genome-wide in the absence of mRNA-rRNA base-pairing
Shine-Dalgarno (SD) motifs are thought to play an important role in translational initiation in bacteria. Paradoxically, ribosome profiling studies inE. coli show no correlation between the strength of an mRNA's SD motif and how efficiently it is translated. Performing profiling on ribosomes with altered anti-Shine-Dalgarno sequences, we reveal a genome-wide correlation between SD strength and ribosome occupancy that was previously masked by other contributing factors. Using the antibiotic retapamulin to trap initiation complexes at start codons, we find that the mutant ribosomes select start sites correctly, arguing that ...
Source: eLife - February 17, 2020 Category: Biomedical Science Tags: Chromosomes and Gene Expression Source Type: research

Neonatal-derived IL-17 producing dermal γδ T cells are required to prevent spontaneous atopic dermatitis
Atopic Dermatitis (AD) is a T cell-mediated chronic skin disease and is associated with altered skin barrier integrity. Infants with mutations in genes involved in tissue barrier fitness are predisposed towards inflammatory diseases, but most do not develop or sustain the diseases, suggesting that there exist regulatory immune mechanisms to prevent aberrant inflammation. The absence of one single murine dermal cell type, the innate neonatal-derived IL-17 producing γδ T (Tγδ17) cells, from birth resulted in spontaneous, highly penetrant AD with many of the major hallmarks of human AD. In Tγ&del...
Source: eLife - February 17, 2020 Category: Biomedical Science Tags: Immunology and Inflammation Source Type: research

Determining the scale at which variation in a single gene changes population yields
Plant trait diversity is known to influence population yield, but the scale at which this happens remains unknown: divergent individuals might change yields of immediate neighbors (neighbor scale) or of plants across a population (population scale). We useNicotiana attenuata plants silenced in mitogen-activated protein kinase 4 (irMPK4) – with low water-use efficiency (WUE) – to study the scale at which water-use traits alter intraspecific population yields. In the field and glasshouse, we observed overyielding in populations with low percentages of irMPK4 plants, unrelated to water-use phenotypes. Paired-plant...
Source: eLife - February 14, 2020 Category: Biomedical Science Tags: Ecology Plant Biology Source Type: research

Correction: A role for phagocytosis in inducing cell death during thymocyte negative selection
(Source: eLife)
Source: eLife - February 14, 2020 Category: Biomedical Science Tags: Cell Biology Immunology and Inflammation Source Type: research

Functional heterogeneity of lymphocytic patterns in primary melanoma dissected through single-cell multiplexing
In melanoma, the lymphocytic infiltrate is a prognostic parameter classified morphologically into 'brisk', 'non-brisk' and 'absent' entailing a functional association that has never been proved. Recently, it has been shown that lymphocytic populations can be very heterogeneous, and that anti-PD-1 immunotherapy supports activated T cells. Here, we characterize the immune landscape in primary melanoma by high-dimensional single cell multiplex analysis in tissue sections (MILAN technique) followed by image analysis, RT-PCR and shotgun proteomics. We observed that the brisk and non-brisk patterns are heterogeneous functional c...
Source: eLife - February 14, 2020 Category: Biomedical Science Tags: Cancer Biology Source Type: research

Suppressing proteasome mediated processing of Topoisomerase II DNA-protein complexes preserves genome integrity
Topoisomerase II (TOP2) relieves topological stress in DNA by introducing double-strand breaks (DSBs) via a transient, covalently linked TOP2 DNA-protein intermediate, termed TOP2 cleavage complex (TOP2cc). TOP2ccs are normally rapidly reversible, but can be stabilized by TOP2 poisons, such as the chemotherapeutic agent etoposide (ETO). TOP2 poisons have shown significant variability in their therapeutic effectiveness across different cancers for reasons that remain to be determined. One potential explanation for the differential cellular response to these drugs is in the manner by which cells process TOP2ccs. Cells are th...
Source: eLife - February 14, 2020 Category: Biomedical Science Tags: Genetics and Genomics Source Type: research

LRRK2 maintains mitochondrial homeostasis and regulates innate immune responses to < i > Mycobacterium tuberculosis < /i >
The Parkinson's Disease (PD)-associated gene leucine-rich repeat kinase (LRRK2) has been studied extensively in the brain. However, several studies have established that mutations in LRRK2 confer susceptibility to mycobacterial infection, suggesting LRRK2 also controls immunity. We demonstrate that loss of LRRK2 in macrophages induces elevated basal levels of type I interferons (IFN) and interferon stimulated genes (ISGs) and causes blunted interferon responses to mycobacterial pathogens and cytosolic nucleic acid agonists. Altered innate immune gene expression inLrrk2 knockout (KO) macrophages is driven by a combination o...
Source: eLife - February 14, 2020 Category: Biomedical Science Tags: Immunology and Inflammation Microbiology and Infectious Disease Source Type: research

Competition between kinesin-1 and myosin-V defines < i > Drosophila < /i > posterior determination
In this study, we use Staufen, an RNA-binding protein that colocalizes withosk mRNA, as a proxy forosk mRNA. We demonstrate that posterior localization ofosk/Staufen is determined by competition between kinesin-1 and myosin-V. While kinesin-1 removesosk/Staufen from the cortex along microtubules, myosin-V anchorsosk/Staufen at the cortex. Myosin-V wins over kinesin-1 at the posterior pole due to low microtubule density at this site, while kinesin-1 wins at anterior and lateral positions because they have high density of cortically-anchored microtubules. As a result, posterior determinants are removed from the anterior and ...
Source: eLife - February 14, 2020 Category: Biomedical Science Tags: Cell Biology Source Type: research

Medial entorhinal cortex activates in a traveling wave in the rat
Traveling waves are hypothesized to support the long-range coordination of anatomically distributed circuits. Whether separate strongly-interacting circuits exhibit traveling waves remains unknown. The hippocampus exhibits traveling 'theta' waves and interacts strongly with the medial entorhinal cortex (MEC). To determine whether the MEC also activates in a traveling wave, we performed extracellular recordings of LFP and multi-unit activity along the MEC. These recordings revealed progressive phase shifts in activity, indicating that the MEC also activates in a traveling wave. Variation in theta waveform along the region, ...
Source: eLife - February 14, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

The speed of GTP hydrolysis determines GTP cap size and controls microtubule stability
Microtubules are cytoskeletal polymers whose function depends on their property to switch between states of growth and shrinkage. Growing microtubules are thought to be stabilized by a GTP cap at their ends. The nature of this cap, however, is still poorly understood. End Binding proteins (EBs) recruit a diverse range of regulators of microtubule function to growing microtubule ends. Whether the EB binding region is identical to the GTP cap is unclear. Using mutated human tubulin with blocked GTP hydrolysis, we demonstrate that EBs bind with high affinity to the GTP conformation of microtubules. Slowing-down GTP hydrolysis...
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Cell Biology Source Type: research

Energy efficient synaptic plasticity
Many aspects of the brain's design can be understood as the result of evolutionary drive towards metabolic efficiency. In addition to the energetic costs of neural computation and transmission, experimental evidence indicates that synaptic plasticity is metabolically demanding as well. As synaptic plasticity is crucial for learning, we examine how these metabolic costs enter in learning. We find that when synaptic plasticity rules are naively implemented, training neural networks requires extremely large amounts of energy when storing many patterns. We propose that this is avoided by precisely balancing labile forms of syn...
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Mechanisms of chromosome biorientation and bipolar spindle assembly analyzed by computational modeling
The essential functions required for mitotic spindle assembly and chromosome biorientation and segregation are not fully understood, despite extensive study. To illuminate the combinations of ingredients most important to align and segregate chromosomes and simultaneously assemble a bipolar spindle, we developed a computational model of fission-yeast mitosis. Robust chromosome biorientation requires progressive restriction of attachment geometry, destabilization of misaligned attachments, and attachment force dependence. Large spindle length fluctuations can occur when the kinetochore-microtubule attachment lifetime is lon...
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Cell Biology Computational and Systems Biology Source Type: research

The CHORD protein CHP-1 regulates EGF receptor trafficking and signaling in < i > C. elegans < /i > and human cells
The intracellular trafficking of growth factor receptors determines the activity of their downstream signaling pathways. Here, we show that he putative HSP-90 co-chaperone CHP-1 acts as a regulator of EGFR trafficking inC. elegans. Loss ofchp-1causes the retention of the EGFR in the ER and decreases MAPK signaling. CHP-1 is specifically required for EGFR trafficking, as the localization of other transmembrane receptors is unaltered inchp-1(lf)mutants, and the inhibition ofhsp-90 or other co-chaperones does not affect EGFR localization. The role of the CHP-1 homolog CHORDC1 during EGFR trafficking is conserved in human cell...
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Cell Biology Developmental Biology Source Type: research

Nodal β spectrins are required to maintain Na < sup > + < /sup > channel clustering and axon integrity
Clustered ion channels at nodes of Ranvier are critical for fast action potential propagation in myelinated axons. Axon-glia interactions converge on ankyrin and spectrin cytoskeletal proteins to cluster nodal Na+ channels during development. However, how nodal ion channel clusters are maintained is poorly understood. Here, we generated mice lacking nodal spectrins in peripheral sensory neurons to uncouple their nodal functions from their axon initial segment functions. We demonstrate a hierarchy of nodal spectrins, where β4 spectrin is the primary spectrin and β1 spectrin can substitute; each is sufficient for p...
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

Moving proteins along in the cilium
The structures of the bovine and human BBSome reveal that a conformational change is required to recruit the complex to the ciliary membrane. (Source: eLife)
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

Regulation of mRNA translation by a photoriboswitch
Optogenetic tools have revolutionized the study of receptor-mediated processes, but such tools are lacking for RNA-controlled systems. In particular, light-activated regulatory RNAs are needed for spatiotemporal control of gene expression. To fill this gap, we usedin vitroselection to isolate a novel riboswitch that selectively binds thetrans isoform of a stiff-stilbene (amino-tSS) –a rapidly and reversibly photoisomerizing small molecule. Structural probing revealed that the RNA binds amino-tSS about 100-times stronger than thecisphotoisoform (amino-cSS).In vitroandin vivofunctional analysis showed that the riboswit...
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Source Type: research

Paradoxical network excitation by glutamate release from VGluT3 < sup > + < /sup > GABAergic interneurons
In violation of Dale's principle several neuronal subtypes utilize more than one classical neurotransmitter. Molecular identification of vesicular glutamate transporter 3 and cholecystokinin expressing cortical interneurons (CCK+VGluT3+INTs) has prompted speculation of GABA/glutamate corelease from these cells for almost two decades despite a lack of direct evidence. We unequivocally demonstrate CCK+VGluT3+INT mediated GABA/glutamate cotransmission onto principal cells in adult mice using paired recording and optogenetic approaches. Although under normal conditions, GABAergic inhibition dominates CCK+VGluT3+INT signaling, ...
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

A large-scale resource for tissue-specific CRISPR mutagenesis in < i > Drosophila < /i >
Genetic screens are powerful tools for the functional annotation of genomes. In the context of multicellular organisms, interrogation of gene function is greatly facilitated by methods that allow spatial and temporal control of gene abrogation. Here, we describe a large-scale transgenic short guide (sg) RNA library for efficient CRISPR-based disruption of specific target genes in a constitutive or conditional manner. The library consists currently of more than 2600 plasmids and 1700 fly lines with a focus on targeting kinases, phosphatases and transcription factors, each expressing two sgRNAs under control of the Gal4/UAS ...
Source: eLife - February 13, 2020 Category: Biomedical Science Tags: Developmental Biology Genetics and Genomics Source Type: research

Noninvasive quantification of axon radii using diffusion MRI
Axon caliber plays a crucial role in determining conduction velocity and, consequently, in the timing and synchronization of neural activation. Noninvasive measurement of axon radii could have significant impact on the understanding of healthy and diseased neural processes. Until now, accurate axon radius mapping has eluded in vivo neuroimaging, mainly due to a lack of sensitivity of the MRI signal to micron-sized axons. Here, we show how – when confounding factors such as extra-axonal water and axonal orientation dispersion are eliminated – heavily diffusion-weighted MRI signals become sensitive to axon radii....
Source: eLife - February 12, 2020 Category: Biomedical Science Tags: Neuroscience Source Type: research

JMJD6 cleaves MePCE to release positive transcription elongation factor b (P-TEFb) in higher eukaryotes
In this report, we utilize mouse and human models to reveal methylphosphate capping enzyme (MePCE), a core component of the 7SK snRNP complex, as the cognate substrate for Jumonji domain-containing 6 (JMJD6) ’s novel proteolytic function. Our evidences consist of a crystal structure of JMJD6 bound to methyl-arginine, enzymatic assays of JMJD6 cleaving MePCEin vivoand in vitro, binding assays, and downstream effects ofJmjd6knockout and overexpression on Pol II CTD phosphorylation. We propose that JMJD6 assists bromodomain containing 4 (BRD4) to recruit P-TEFb to Pol II CTD by disrupting the 7SK snRNP complex. (Source: eLife)
Source: eLife - February 12, 2020 Category: Biomedical Science Tags: Biochemistry and Chemical Biology Source Type: research