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bioRxiv2020

Morpho-physiological and gene expression responses of wheat by Aegilops cylindrica amphidiploids to salt stress

Aegilops cylindrica Host is one of the most salt-tolerant species in the Triticeae tribe. Amphidiploid plants derived from hybridization of Roshan x Aegilops cylindrica and Chinese Spring x Ae. cylindrica genotypes contrasting in salt tolerance were assessed for their morpho-physiological responses and the expression patterns of three genes related to ion homeostasis under 250 mM NaCl. Results showed that salt stress caused significant declines in both their morphological and phenological traits. Moreover, salt stress reduced not only their chlorophyll content but also their root and shoot K contents and K/Na ratios, while it led to significant enhancements in the remaining traits. Similar to Ae. cylindrica, the amphidiploids subjected to salt stress exhibited significantly higher H2O2 levels, root and shoot K contents, and root and shoot K/Na ratios accompanied by lower root and shoot Na contents and MDA concentrations when compared with the same traits in the wheat parents. Quantitative Real-Time PCR showed significant differential expression patterns of the HKT1;5, NHX1, and SOS1 genes between the amphidiploids and their parents. The transcript level of HKT1;5 was found to be higher in the roots than in the shoots of both the amphidiploids and Ae. cylindrica while NHX1 exhibited a higher expression in the shoot tissues. The consistency of these data provides compelling support for the hypothesis that active exclusion of Na from the roots and elevated vacuolar sequestration of Na in the leaves might explain the declining Na levels in the shoots and roots of both the amphidiploids and Ae. cylindrica relative to those measured in wheat parents. It is concluded that the hybridized amphiploids are potentially valuable resources for salt improvement in bread wheat through the backcrossing approach.

plant biology↗

bioRxiv2020

Rhesus macaques as a tractable physiological model of human ageing

Research in the basic biology of ageing is increasingly identifying mechanisms and modifiers of ageing in short-lived organisms such as worms and mice. The ultimate goal of such work is to improve human health, particularly in the growing segment of the population surviving into old age. Thus far, few interventions have robustly transcended species boundaries in the laboratory, suggesting that changes in approach are needed to avoid costly failures in translational human research. In this review, we discuss both well-established and alternative model organisms for ageing research and outline how research in nonhuman primates is sorely needed, first, to translate findings from shorter-lived organisms to humans, and second, to understand key aspects of ageing that are unique to primate biology. We focus on rhesus macaques as a particularly promising model organism for ageing research due to their social and physiological similarity to humans as well as the existence of key resources that have been developed for this species. As a case study, we compare gene regulatory signatures of ageing in the peripheral immune system between humans and rhesus macaques from a free-ranging study population in Cayo Santiago. We show that both mRNA expression and DNA methylation signatures of immune ageing are broadly shared between macaques and humans, indicating strong conservation of the trajectory of ageing in the immune system. We conclude with a review of key issues in the biology of ageing for which macaques and other nonhuman primates may uniquely contribute valuable insights, including the effects of social gradients on health and ageing. We anticipate that continuing research in rhesus macaques and other nonhuman primates will play a critical role in conjunction with model organism and human biodemographic research in ultimately improving translational outcomes and extending health and longevity in our ageing population.

genomics↗

bioRxiv2020

Chemical-genetic interrogation of RNA polymerase mutants reveals structure-function relationships and physiological tradeoffs

The multi-subunit bacterial RNA polymerase (RNAP) and its associated regulators carry out transcription and integrate myriad regulatory signals. Numerous studies have interrogated the inner workings of RNAP, and mutations in genes encoding RNAP drive adaptation of Escherichia coli to many health- and industry-relevant environments, yet a paucity of systematic analyses has hampered our understanding of the fitness benefits and trade-offs from altering RNAP function. Here, we conduct a chemical-genetic analysis of a library of RNAP mutants. We discover phenotypes for non-essential insertions, show that clustering mutant phenotypes increases their predictive power for drawing functional inferences, and illuminate a connection between transcription and cell division. Our findings demonstrate that RNAP chemical-genetic interactions provide a general platform for interrogating structure-function relationships in vivo and for identifying physiological trade-offs of mutations, including those relevant for disease and biotechnology. This strategy should have broad utility for illuminating the role of other important protein complexes.Competing Interest StatementThe authors have declared no competing interest.View Full Text

systems biology↗

bioRxiv2020

Multiplexed mRNA assembly into ribonucleoprotein particles plays an operon-like role in the control of yeast cell physiology

Prokaryotes utilize polycistronic messages (operons) to co-translate proteins involved in the same biological process. Whether eukaryotes achieve similar regulation by selectively assembling monocistronic messages derived from different chromosomes is unclear. We employed transcript-specific RNA pulldowns and RNA-seq/RT-PCR to identify mRNAs that co-precipitate into ribonucleoprotein (RNP) particles in yeast. Consistent with the hypothesis of eukaryotic RNA operons, mRNAs encoding components of the mating pathway, heat shock proteins, and mitochondrial outer membrane proteins multiplex in trans to form discrete mRNP particles, termed transperons. Chromatin-capture experiments reveal that genes encoding multiplexed mRNAs physically interact, thus, RNA assembly may result from co-regulated gene expression. Transperon assembly and function depends upon H4 histones and their depletion leads to defects in RNA multiplexing, resulting in decreased pheromone responsiveness and mating, and increased heat shock sensitivity. We propose that intergenic associations and non-canonical H4 histone functions contribute to transperon formation in eukaryotic cells to regulate cell physiology. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

cell biology↗

bioRxiv2020

Loop Extrusion Mediates Physiological Locus Contraction for V(D)J Recombination

Immunoglobulin heavy chain locus (Igh) VH, D, and JH gene segments are developmentally assembled into V(D)J exons. RAG endonuclease initiates V(D)J recombination by binding a JH-recombination signal sequence (RSS) within a chromatin-based recombination center (RC) and then, in an orientation-dependent process, scans upstream D-containing chromatin presented by cohesin-mediated loop extrusion for convergent D-RSSs to initiate DJH-RC formation1,2. In primary pro-B cells, 100s of upstream VH-associated RSSs, embedded in convergent orientation to the DJH-RC-RSS, gain proximity to the DJH-RC for VH-to-DJH joining via a mechanistically-undefined VH-locus contraction process3-7. Here, we report that a 2.4 mega-base VH locus inversion in primary pro-B cells nearly abrogates rearrangements of normally convergent VH-RSSs and cryptic RSSs, even though locus contraction per se is maintained. Moreover, this inversion activated rearrangement of both cryptic VH-locus RSSs normally in the opposite orientation and, unexpectedly, of normally-oriented cryptic RSSs within multiple, sequential upstream convergent-CBE domains. Primary pro-B cells had significantly reduced transcription of Wapl8, a cohesin-unloading factor, versus levels in v-Abl pro-B lines that lack marked locus contraction or distal VH rearrangements2,9-11. Correspondingly, Wapl depletion in v-Abl lines activated VH-locus contraction and orientation-specific RAG-scanning across the VH-locus. Our findings indicate that locus contraction and physiological VH-to-DJH joining both are regulated via circumvention of CBE scanning impediments.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗

bioRxiv2020

Network rewiring: physiological consequences of reciprocally exchanging the physical locations and growth-phase-dependent expression patterns of the Salmonella fis and dps genes

ABSTRACTThe Fis nucleoid-associated protein controls the expression of a large and diverse regulon of genes in Gram-negative bacteria. Fis production is normally maximal in bacteria during the early exponential phase of batch culture growth, becoming almost undetectable by the onset of stationary phase. We tested the effect on the Fis regulatory network in Salmonella of moving the complete fis gene from its usual location near the origin of chromosomal replication to the position normally occupied by the dps gene in the Right macrodomain of the chromosome, and vice versa, creating the strain GX. In a parallel experiment, we tested the effect of rewiring the Fis regulatory network by placing the fis open reading frame under the control of the stationary-phase-activated dps promoter at the dps genetic location within Ter, and vice versa, creating the strain OX. ChIP-seq was used to measure global Fis protein binding and gene expression patterns. Strain GX showed few changes when compared with the wild type, although we did detect increased Fis binding at Ter, accompanied by reduced binding at Ori. Strain OX displayed a more pronounced version of this distorted Fis protein-binding pattern together with numerous alterations in the expression of genes in the Fis regulon. OX, but not GX, had a reduced ability to infect cultured mammalian cells. These findings illustrate the inherent robustness of the Fis regulatory network to rewiring based on gene repositioning alone and emphasise the importance of fis expression signals in phenotypic determination.IMPORTANCE We assessed the impacts on Salmonella physiology of reciprocally translocating the genes encoding the Fis and Dps nucleoid-associated proteins (NAPs), and of inverting their growth phase production patterns such that Fis is produced in stationary phase (like Dps) and Dps is produced in exponential phase (like Fis). Changes to peak binding of Fis were detected by ChIP-seq on the chromosome, as were widespread impacts on the transcriptome, especially when Fis production mimicked Dps. Virulence gene expression and the expression of a virulence phenotype were altered. Overall, these radical changes to NAP gene expression were well tolerated, revealing the robust and well-buffered nature of global gene regulation networks in the bacterium.Competing Interest StatementThe authors have declared no competing interest.View Full Text

microbiology↗

bioRxiv2020

Structural models of mitochondrial uncoupling proteins obtained in DPC micelles are not physiologically relevant for their uncoupling activity.

Uncoupling protein 1 (UCP1) is found in the inner mitochondrial membrane of brown adipocyte. In the presence of long-chain fatty acids (LCFA), UCP1 increases the proton conductance, which, in turn, increases fatty acid oxidation and energy release as heat. Several atomic models of UCP1 and UCP2 have been obtained by NMR in dodecylphosphocholine (DPC), a detergent known to inactivate UCP1. Based on NMR titration experiment on UCP1 with LCFA, it has been proposed that K56 and K269 are crucial for LCFA binding and UCP1 activation. Given the numerous controversies on the use of DPC for structure-function analyses of membrane proteins, we revisited those UCP1 mutants in a more physiological context by expressing them in the mitochondria of S. cerevisiae. Mitochondrial respiration, assayed on permeabilized spheroplasts, enables the determination of UCP1 activation and inhibition. The K56S, K269S and K56S/K269S mutants did not display any default in activation, which shows that the NMR experiments in DPC detergent are not relevant to understand UCP1 function.

biochemistry↗

bioRxiv2020

Optical measurement of physiological sodium currents in the axon initial segment

In most neurons of the mammalian central nervous system, the action potential (AP) is triggered in the axon initial segment (AIS) by a fast Na+ current mediated by voltage-gated Na+ channels. The intracellular Na+ increase associated with the AP has been measured using fluorescent Na+ indicators, but with insufficient resolution to resolve the Na+ current in the AIS. In this article, we report the critical improvement in temporal resolution of the Na+ imaging technique allowing the direct experimental measurement of Na+ currents in the AIS. We determined the AIS Na+ current, from fluorescence measurements at temporal resolution of 100 {micro}s and pixel resolution of half a micron, in pyramidal neurons of the layer-5 of the somatosensory cortex from brain slices of the mouse. We identified a subthreshold current before the AP, a fast inactivating current peaking during the rise of the AP and a persistent current during the AP repolarisation. We correlated the kinetics of the current at different distances from the soma with the kinetics of the somatic AP. We quantitatively compared the experimentally measured Na+ current with the current obtained by computer simulation of published NEURON models and we show how the present approach can lead to the correct estimate of the native behaviour of Na+ channels. Thus, it is expected that the present method will be adopted to investigate the function of different channel types under physiological or pathological conditions.

neuroscience↗

bioRxiv2020

Estimation of Laminar BOLD Activation Profiles using Deconvolution with a Physiological Point Spread Function

BackgroundThe specificity of gradient echo (GE)-BOLD laminar fMRI activation profiles is degraded by intracortical veins that drain blood from lower to upper cortical layers, propagating activation signal in the same direction. This work describes an approach to obtain layer specific profiles by deconvolving the measured profiles with a physiological Point Spread Function (PSF). New MethodIt is shown that the PSF can be characterised by a TE-dependent peak to tail (p2t) value that is independent of cortical depth and can be estimated by simulation. An experimental estimation of individual p2t values and the sensitivity of the deconvolved profiles to variations in p2t is obtained using laminar data measured with a multi-echo 3D-FLASH sequence. These profiles are echo time dependent, but the underlying neuronal response is the same, allowing a data-based estimation of the PSF. ResultsThe deconvolved profiles are highly similar to the gold-standard obtained from extremely high resolution 3D-EPI data, for a range of p2t values of 5-9, which covers both the empirically determined value (7.1) and the value obtained by simulation (6.3). Comparison with Existing Method(s)Corrected profiles show a flatter shape across the cortex and a high level of similarity with the gold-standard, defined as a subset of profiles that are unaffected by intracortical veins. ConclusionsWe conclude that deconvolution is a robust approach for removing the effect of signal propagation through intracortical veins. This makes it possible to obtain profiles with high laminar specificity while benefitting from the higher sensitivity and efficiency of GE-BOLD sequences.

neuroscience↗

bioRxiv2020

Expression of ACE2, TMPRSS2, and CTSL in human airway epithelial cells under physiological and pathological conditions: Implications for SARS-CoV2 infection

SARS-CoV-2 enters into human airway epithelial cells via membrane fusion or endocytosis, and this process is dependent on ACE2, TMPRSS2, and cathepsin L. In this study, we examined the expression profiles of the three SARS-CoV-2 entry-related genes in primary human airway epithelial cells isolated from donors with different physiological and pathological backgrounds such as smoking, COPD, asthma, lung cancer, allergic rhinitis, cystic fibrosis, or viral infections. By reanalyzing 54 GEO datasets comprising transcriptomic data of 3428 samples, this study revealed that i) smoking is associated with an increased expression of ACE2 and TMPRSS2 and a decreased expression of cathepsin L; ii) infection of rhinovirus as well as poly(I:C) stimulation leads to high expression of all three SARS-CoV-2 entry-related genes; iii) expression of ACE2 and cathepsin L in nasal epithelial cells are decreased in patients with asthma and allergic rhinitis. In conclusion, this study implicates that infection of respiratory viruses, cigarette smoking and allergic respiratory diseases might affect the susceptibility to and the development of COVID-19.

pathology↗

bioRxiv2020

Leptin signaling regulates physiological damage and host-pathogen cooperation

To combat infections, hosts employ a combination of antagonistic and cooperative defense strategies. The former refers to pathogen killing mediated by resistance mechanisms, while the latter refers to physiological defense mechanisms that promote host health during infection independent of pathogen killing, leading to an apparent cooperation between the host and the pathogen. Previous work has shown that leptin, a pleiotropic hormone that plays a central role in regulating appetite and energy metabolism, is indispensable for resistance mechanisms, while a role for leptin signaling in cooperative host-pathogen interactions remains unknown. Using a mouse model of Yersinia pseudotuberculosis (Yptb) infection, the causative agent of Far East scarlet-like fever, we unexpectedly found that genetic inhibition of leptin signaling conferred protection from Yptb infection due to increased host-pathogen cooperation rather than greater resistance defenses. The protection against Yptb infection was not due to differences in food consumption, lipolysis or fat mass. Furthermore, we found that the survival advantage was associated with increased liver damage and dysfunction. Our work reveals an additional level of complexity for the role of leptin in infection defense and suggests that in some contexts, in addition to tolerating the pathogen, tolerating organ damage and dysfunction is more beneficial for survival than preventing the damage.

immunology↗

bioRxiv2020

Effects of a combined enrichment intervention on the behavioural and physiological welfare of captive Asiatic lions (Panthera leo persica)

The endangered Asiatic lion (Panthera leo persica) is currently distributed as a single wild population of 670 individuals and [~]400 captive animals globally. Although the captive lions are major hope for the species long-term conservation through repatriation, their welfare status and management practises need research attention. To this end, we tested the efficacy of feeding, sensory and manipulable enrichment interventions on the welfare of Asiatic lions at the conservation breeding centre of Sakkarbaug Zoological Garden, Gujarat. We adopted a holistic approach by measuring physiological and behavioural responses of 35 captive Asiatic lions, divided into control (n=16) and test (n=19) groups. The test subjects approached feeding devices first and manipulable devices for a longer duration. Manipulable devices were used homogenously with two significant time peaks, but sensory devices were used sporadically throughout the day with no discernible peak usage. The control subjects remained unchanged in all welfare parameters compared to their pre-treatment levels. However, post-enrichment behavioural assessments showed higher behaviour diversity (95% increase from the baseline period), reduced enclosure zone bias (40.25% reduction) and aberrant repetitive behaviours (80.68%) in test samples. Similarly, faecal corticosterone measures showed lower stress levels in test samples (58% decrease), confirming significant improvement in all welfare indices than control groups. These results have universal applicability to assess welfare indices of other captive species in Indian zoos. We hope that the results will encourage zoo managers and regulatory agencies to improve animal welfare practices.

animal behavior and cognition↗

bioRxiv2020

Induced Disassembly of a Virus-Like Particle under Physiological Conditions for Venom Peptide Delivery

Virus-like nanoparticles (VLPs) show considerable promise for the in vivo delivery of therapeutic compounds such as bioactive venom peptides. While loading and targeting protocols have been developed for numerous VLP prototypes, induced disassembly under physiological conditions of neutral pH, moderate temperature, and aqueous medium, remain a challenge. Here, we implement and evaluate a ring-opening metathesis polymerization (ROMP) general mechanism for controllable VLP disassembly that is independent of cell-specific factors or the manipulation environmental conditions such as pH and temperature that cannot be readily controlled in vivo. The ROMP substrate norbornene is covalently conjugated to surface-exposed lysine residues of a P22 bacteriophage-derived VLP, and ROMP is induced by treatment of water-soluble ruthenium catalyst AquaMet. Disruption of the P22 shell and release of a GFP reporter is confirmed via native agarose electrophoresis and quantitative microscopy and light scattering analyses. Our ROMP disassembly strategy does not depend on the particular structure or morphology of the P22 nanocontainer and is adaptable to other VLP prototypes for the potential delivery of venom peptides for pharmacological applications. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=90 SRC="FIGDIR/small/278598v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@1d24020org.highwire.dtl.DTLVardef@702e3aorg.highwire.dtl.DTLVardef@eb0d25org.highwire.dtl.DTLVardef@1ac00d0_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2020

Kcns3 Deficiency Disrupts Parvalbumin Neuron Physiology in Mouse Prefrontal Cortex: Implications for the pathophysiology of schizophrenia

The unique fast spiking (FS) phenotype of cortical parvalbumin-positive (PV) neurons depends on multiple subtypes of voltage-gated potassium channels (Kv). PV neurons selectively express Kcns3, the gene encoding Kv9.3 subunits, suggesting that Kcns3 expression is critical for the FS phenotype. KCNS3 expression is lower in PV neurons in schizophrenia, but the effects of this alteration are unclear, because Kv9.3 subunit function is poorly understood. We therefore assessed the role of Kv9.3 subunits in PV neuron function by combining gene expression analyses, computational modeling, and electrophysiology in acute slices from the cortex of Kcns3-deficient mice Kcns3 mRNA levels were ~50% lower in cortical PV neurons from Kcns3-deficient relative to wildtype mice. While silent per se, Kv9.3 subunits are believed to amplify the Kv2.1 current in Kv2.1-Kv9.3 channel complexes. Hence, to assess the consequences of reducing Kv9.3 levels, we simulated the effects of decreasing the Kv2.1-mediated current in a computational model. The FS cell model with reduced Kv2.1 produced spike trains with irregular inter-spike intervals, or stuttering, and greater Na+ channel inactivation, possibly due to a smaller afterhyperpolarization. As in the computational model, PV basket cells (PVBCs) from Kcns3-deficient mice displayed spike trains with strong stuttering, which depressed PVBC firing, and smaller afterhyperpolarization. Moreover, Kcns3 deficiency impaired the recruitment of PVBCs by stimuli mimicking synaptic input during cortical UP states, which elicited bursts of spikes at gamma frequency. Our data suggest that Kv9.3 subunits are critical for PVBC physiology, and that KCNS3 deficiency in schizophrenia may impair the substrate of gamma oscillations. Significance statementIn the neocortex, Kcns3, the gene encoding voltage-dependent potassium (Kv) channel subunits Kv9.3, is selectively expressed by parvalbumin-positive (PV) neurons. Moreover, KCNS3 expression is decreased in PV neurons in schizophrenia. Kv 9.3 subunits are believed to amplify the current mediated by Kv2.1 subunits, however Kv9.3 function has not been investigated in PV cells. Here, simulations in a computational model and electrophysiological experiments with Kcns3-deficient mice revealed that Kcns3 deficiency disrupts repetitive firing in cortical PV neurons, possibly enhancing Na+ channel inactivation, and particularly with stimuli eliciting firing at gamma frequency band (30-80Hz). Our results suggest that Kv9.3 subunits are essential for PV neuron electrophysiology and that KCNS3 deficiency likely contributes to PV neuron dysfunction and gamma oscillation impairments in schizophrenia.

neuroscience↗

bioRxiv2020

Cholesterol in membranes facilitates aggregation of amyloid beta protein at physiologically low concentrations

The formation of amyloid {beta} (1-42) (A{beta}42) oligomers is considered to be a critical step in the development of Alzheimers disease (AD). However, the mechanism underlying this process at physiologically low concentrations of A{beta}42 remains unclear. We have previously shown that oligomers assemble at such low A{beta}42 monomer concentrations in vitro on phospholipid membranes. We hypothesized that membrane composition is the factor controlling the aggregation process. Accumulation of cholesterol in membranes is associated with AD development, suggesting that insertion of cholesterol into membranes may initiate the A{beta}42 aggregation, regardless of a low monomer concentration. We used atomic force microscopy (AFM) to directly visualize the aggregation process of A{beta}42 on the surface of a lipid bilayer containing cholesterol. Time-lapse AFM imaging unambiguously demonstrates that cholesterol in the lipid bilayer significantly enhances the aggregation process of A{beta}42 at nanomolar monomer concentration. Quantitative analysis of the AFM data shows that both the number of A{beta}42 oligomers and their sizes grow when cholesterol is present. Importantly, the aggregation process is dynamic, so the aggregates assembled on the membrane can dissociate from the bilayer surface into the bulk solution. Computational modeling demonstrated that the lipid bilayer containing cholesterol had an elevated affinity to A{beta}42. Moreover, monomers adopted the aggregation-prone conformations present in amyloid fibrils. The low energy barriers between these conformations facilitate the transition between monomer states and is another factor promoting the self-association of the monomers.

biophysics↗

bioRxiv2020

Near-Physiological-Temperature Serial Femtosecond X-ray Crystallography Reveals Novel Conformations of SARS-CoV-2 Main Protease Active Site for Improved Drug Repurposing

The COVID19 pandemic has resulted in 25+ million reported infections and nearly 850.000 deaths. Research to identify effective therapies for COVID19 includes: i) designing a vaccine as future protection; ii) structure-based drug design; and iii) identifying existing drugs to repurpose them as effective and immediate treatments. To assist in drug repurposing and design, we determined two apo structures of Severe Acute Respiratory Syndrome CoronaVirus-2 main protease at ambienttemperature by Serial Femtosecond X-ray crystallography. We employed detailed molecular simulations of selected known main protease inhibitors with the structures and compared binding modes and energies. The combined structural biology and molecular modeling studies not only reveal the dynamics of small molecules targeting main protease but will also provide invaluable opportunities for drug repurposing and structure-based drug design studies against SARS-CoV-2. One Sentence SummaryRadiation-damage-free high-resolution SARS-CoV-2 main protease SFX structures obtained at near-physiological-temperature offer invaluable information for immediate drug-repurposing studies for the treatment of COVID19.

biophysics↗

bioRxiv2020

The protected physiological status of intracellular Salmonella enterica persisters reduces host cell-imposed stress

Today, we are faced with increasingly occurring bacterial infections that are hard to treat and often tend to relapse. These recurrent infections can occur possibly due to antibiotic-tolerant persister cells. Antibiotic persistent bacteria represent a small part of a bacterial population that enters a non-replicating (NR) state arising from phenotypic switching. Intracellularly, after uptake by phagocytic cells, Salmonella enterica serovar Typhimurium (STM) forms persister cells that are able to subvert immune defenses of the host. However, the clear physiological state and perceptual properties are still poorly understood and many questions remain unanswered. Here we describe further development of fluorescent protein-based reporter plasmids that were used to detect intracellular NR persister cells and monitor the expression of stress response genes via extensive flow cytometric analyses. Moreover, we performed extensive measurements of the metabolic properties of NR STM at the early course of infection. Our studies demonstrate that NR STM persister cells perceive their environment and are capable respond to stress factors. Since persisters showed a lower stress response compared to replicating (R) STM, which was not a consequence of a lower metabolic capacity, the persistent status of STM serves as protective niche. Furthermore, up to 95% of NR STM were metabolically active at the beginning of infection additionally showing no difference in the metabolic capacity compared to R STM. The accessory capability of NR STM persisters to sense and to react to stress with constant metabolic activity may supports the pathogen to create a more permissive environment for recurrent infections.

microbiology↗

bioRxiv2020

Dopamine neuron synaptic connectivity defines physiological striatal domains

Dopamine neurons projecting to the striatum control movement, cognition, and motivation. They do so via slower, dopamine volume transmission and also via faster synaptic dopamine, glutamate and GABA transmission. To define the scope of these synaptic actions, we recorded dopamine neuron synaptic currents in the four major classes of striatal neurons. This revealed that dopaminergic and GABAergic synaptic actions are widespread; glutamatergic synaptic actions are robust in the medial nucleus accumbens and the anterolateral dorsal striatum, mediating fast and slow excitation, respectively. Dopamine neuron synaptic actions in cholinergic interneurons are the strongest and most complex, involving all three transmitters, their multiple receptors, and are the most regionally heterogeneous. The caudal striatum forms a single domain with overall weak dopamine neuron synaptic actions. This synaptic mapping reveals that dopamine neuron synaptic actions extend across the entire striatum, are regionally heterogeneous and organized in physiological domains, determined mainly by their excitatory actions.

neuroscience↗