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Philippot Q, Casanova JL, Puel A
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Candidiasis in patients with APS-1: low IL-17, high IFN-gamma, or both? (opens in new window)

CURRENT OPINION IN IMMUNOLOGY 2021 OCT; 72(?):318-323
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Chronic mucocutaneous candidiasis (CMC) is one of the earliest and most frequent clinical manifestations of autosomal recessive autoimmune polyendocrine syndrome type 1 (APS1), a monogenic inborn error of immunity caused by deleterious variants of the autoimmune regulator (AIRE) gene. APS-1 patients suffer from various autoimmune diseases, due to the defective thymic deletion of autoreactive T cells, and the development of a large range of autoantibodies (auto-Abs) against various tissue antigens, and some cytokines. The mechanisms underlying CMC remained elusive for many years, until the description in 2010 of high serum titers of neutralizing auto-Abs against IL-17A, IL-17F, and/or IL-22, which are present in almost all APS-1 patients. Excessively high mucosal concentrations of IFN-gamma were recently proposed as an alternative mechanism for CMC in APS-1.
Baez-Mendoza R, Vazquez Y, Mastrobattista EP, Williams ZM
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Neuronal Circuits for Social Decision-Making and Their Clinical Implications (opens in new window)

FRONTIERS IN NEUROSCIENCE 2021 OCT 1; 15(?):? Article 720294
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Social living facilitates individual access to rewards, cognitive resources, and objects that would not be otherwise accessible. There are, however, some drawbacks to social living, particularly when competing for scarce resources. Furthermore, variability in our ability to make social decisions can be associated with neuropsychiatric disorders. The neuronal mechanisms underlying social decision-making are beginning to be understood. The momentum to study this phenomenon has been partially carried over by the study of economic decision-making. Yet, because of the similarities between these different types of decision-making, it is unclear what is a social decision. Here, we propose a definition of social decision-making as choices taken in a context where one or more conspecifics are involved in the decision or the consequences of it. Social decisions can be conceptualized as complex economic decisions since they are based on the subjective preferences between different goods. During social decisions, individuals choose based on their internal value estimate of the different alternatives. These are complex decisions given that conspecifics beliefs or actions could modify the subject's internal valuations at every choice. Here, we first review recent developments in our collective understanding of the neuronal mechanisms and circuits of social decision-making in primates. We then review literature characterizing populations with neuropsychiatric disorders showing deficits in social decision-making and the underlying neuronal circuitries associated with these deficits.
Buitrago L, Lefkowitz S, Bentur O, Padovan J, Allen BC
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Platelet binding to polymerizing fibrin is avidity driven and requires activated aIIbb3 but not fibrin cross-linking (opens in new window)

BLOOD ADVANCES 2021 OCT 26; 5(20):3986-4002
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The molecular basis of platelet-fibrin interactions remains poorly understood despite the predominance of fibrin in thrombi. We have studied the interaction of platelets with polymerizing fibrin by adding thrombin to washed platelets in the presence of the peptide RGDW, which inhibits the initial platelet aggregation mediated by fibrinogen binding to aIIbb3 but leaves intact a delayed increase in light transmission (delayed wave; DW) as platelets interact with the polymerizing fibrin. The DW was absent in platelets from a patient with Glanzmann thrombasthenia, indicating a requirement for aIIbb3. The DW required aIIbb3 activation and it was inhibited by the aIIbb3 antagonists eptifibatide and the monoclonal antibody (mAb) 7E3, but only at much higher concentrations than needed to inhibit platelet aggregation initiated by a thrombin receptor activating peptide (T6). Surface plasmon resonance and scanning electron microscopy studies both supported fibrin having greater avidity for aIIb b3 than fibrinogen rather than greater affinity, consistent with fibrin's multivalency. mAb 10E5, a potent inhibitor of T6-induced platelet aggregation, did not inhibit the DW, suggesting that fibrin differs from fibrinogen in its mechanism of binding. Inhibition of factor XIII-mediated fibrin cross-linking by .95% reduced the DW by only 32%. Clot retraction showed a pattern of inhibition similar to that of the DW. We conclude that activated aIIbb3 is the primary mediator of platelet-fibrin interactions leading to clot retraction, and that the interaction is avidity driven, does not require fibrin cross-linking, and is mediated by a mechanism that differs subtly from that of the interaction of aIIbb3 with fibrinogen.
Kow LM, Kandel H, Kilinc M, Daniels MA, Magarinos AM, Jiang CS, Pfaff DW
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Potassium channels and the development of arousal-relevant action potential trains in primary hindbrain neurons (opens in new window)

BRAIN RESEARCH 2021 OCT 1; 1768(?):? Article 147574
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Neurons in nucleus gigantocellularis (NGC) have been shown by many lines of evidence to be important for regulating generalized CNS arousal. Our previous study on mouse pups suggested that the development of NGC neurons' capability to fire action potential (AP) trains may both lead to the development of behavioral arousal and may itself depend on an increase in delayed rectifier currents. Here with whole-cell patch clamp we studied delayed rectifier currents in two stages. First, primary cultured neurons isolated from E12.5 embryonic hindbrain (HB), a dissection which contains all of NGC, were used to take advantage of studying neurons in vitro over using neurons in situ or in brain slices. HB neurons were tested with Guangxitoxin-1E and Resveratrol, two inhibitors of Kv2 channels which mediate the main bulk of delayed rectifier currents. Both inhibitors depressed delayed rectifier currents, but differentially: Resveratrol, but not Guangxitoxin-1E, reduced or abolished action potentials in AP trains. Since Resveratrol affects the Kv2.2 subtype, the development of the delayed rectifier mediated through Kv2.2 channels may lead to the development of HB neurons' capability to generate AP trains. Stage Two in this work found that electrophysiological properties of the primary HB neurons recorded are essentially the same as those of NGC neurons. Thus, from the two stages combined, we propose that currents mediated through Kv2.2 are crucial for generating AP trains which, in turn, lead to the development of mouse pup behavioral arousal.
Parker J, Kronauer DJC
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How ants shape biodiversity (opens in new window)

CURRENT BIOLOGY 2021 OCT 11; 31(19):R1208-+
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Doane AS, Chu CS, Di Giammartino DC, Rivas MA, Hellmuth JC, Jiang YW, Yusufova N, Alonso A, Roeder RG, Apostolou E, Melnick AM, Elemento O
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OCT2 pre-positioning facilitates cell fate transition and chromatin architecture changes in humoral immunity (opens in new window)

NATURE IMMUNOLOGY 2021 OCT; 22(10):1327-+
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During the germinal center (GC) reaction, B cells undergo profound transcriptional, epigenetic and genomic architectural changes. How such changes are established remains unknown. Mapping chromatin accessibility during the humoral immune response, we show that OCT2 was the dominant transcription factor linked to differential accessibility of GC regulatory elements. Silent chromatin regions destined to become GC-specific super-enhancers (SEs) contained pre-positioned OCT2-binding sites in naive B cells (NBs). These preloaded SE 'seeds' featured spatial clustering of regulatory elements enriched in OCT2 DNA-binding motifs that became heavily loaded with OCT2 and its GC-specific coactivator OCin GC B cells (GCBs). SEs with high abundance of pre-positioned OCT2 binding preferentially formed long-range chromatin contacts in GCs, to support expression of GC-specifying factors. Gain in accessibility and architectural interactivity of these regions were dependent on recruitment of OCAB. Pre-positioning key regulators at SEs may represent a broadly used strategy for facilitating rapid cell fate transitions. Elemento, Melnick and colleagues examine the chromatin and transcriptional changes that occur during differentiation of human primary B cells into antibody-secreting cells. In naive B cells, the transcription factor OCT2 is preloaded at high-affinity super-enhancer sites present in repressed 'silent' chromatin; upon activation, OCis recruited to these regions, where it facilitates arrays of OCT2 binding to lower-affinity octamer motifs, leading to active formation of germinal center B cell-specific super-enhancers.
Abolhassani H, Vosughimotlagh A, Asano T, Landegren N, Boisson B, Delavari S, Bastard P, Aranda-Guillen M, Wang YT, Zuo FL, Sardh F, Marcotte H, Du LK, Zhang SY, Zhang Q, Rezaei N, Kampe O, Casanova JL, Hammarstrom L, Pan-Hammarstrom Q
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X-Linked TLR7 Deficiency Underlies Critical COVID-19 Pneumonia in a Male Patient with Ataxia-Telangiectasia (opens in new window)

JOURNAL OF CLINICAL IMMUNOLOGY
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Background Coronavirus disease 2019 (COVID-19) exhibits a wide spectrum of clinical manifestations, ranging from asymptomatic to critical conditions. Understanding the mechanism underlying life-threatening COVID-19 is instrumental for disease prevention and treatment in individuals with a high risk. Objectives We aimed to identify the genetic cause for critical COVID-19 pneumonia in a patient with a preexisting inborn error of immunity (IEI). Methods Serum levels of specific antibodies against the virus and autoantibodies against type I interferons (IFNs) were measured. Whole exome sequencing was performed, and the impacts of candidate gene variants were investigated. We also evaluated 247 ataxia-telangiectasia (A-T) patients in the Iranian IEI registry. Results We report a 7-year-old Iranian boy with a preexisting hyper IgM syndrome who developed critical COVID-19 pneumonia. IgM only specific COVID-19 immune response was detected but no autoantibodies against type I IFN were observed. A homozygous deleterious mutation in the ATM gene was identified, which together with his antibody deficiency, radiosensitivity, and neurological signs, established a diagnosis of A-T. Among the 247 A-T patients evaluated, 36 had SARS-CoV-2 infection, but all had mild symptoms or were asymptomatic except the index patient. A hemizygous deleterious mutation in the TLR7 gene was subsequently identified in the patient. Conclusions We report a unique IEI patient with combined ATM and TLR7 deficiencies. The two genetic defects underlie A-T and critical COVID-19 in this patient, respectively.
Ghosh S, Cottingham KL, Reuman DC
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Species relationships in the extremes and their influence on community stability (opens in new window)

PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES 2021 OCT 11; 376(1835):? Article 20200343
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Synchrony among population fluctuations of multiple coexisting species has a major impact on community stability, i.e. on the relative temporal constancy of aggregate properties such as total community biomass. However, synchrony and its impacts are usually measured using covariance methods, which do not account for whether species abundances may be more correlated when species are relatively common than when they are scarce, or vice versa. Recent work showed that species commonly exhibit such 'asymmetric tail associations'. We here consider the influence of asymmetric tail associations on community stability. We develop a 'skewness ratio' which quantifies how much species relationships and tail associations modify stability. The skewness ratio complements the classic variance ratio and related metrics. Using multi-decadal grassland datasets, we show that accounting for tail associations gives new viewpoints on synchrony and stability; e.g. species associations can alter community stability differentially for community crashes or explosions to high values, a fact not previously detectable. Species associations can mitigate explosions of community abundance to high values, increasing one aspect of stability, while simultaneously exacerbating crashes to low values, decreasing another aspect of stability; or vice versa. Our work initiates a new, more flexible paradigm for exploring species relationships and community stability. This article is part of the theme issue 'Synchrony and rhythm interaction: from the brain to behavioural ecology'.
Watson KT, Simard JF, Henderson VW, Nutkiewicz L, Lamers F, Nasca C, Rasgon N, Penninx BWJH
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Incident Major Depressive Disorder Predicted by Three Measures of Insulin Resistance: A Dutch Cohort Study (opens in new window)

AMERICAN JOURNAL OF PSYCHIATRY 2021 OCT; 178(10):914-920
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Objective: Major depressive disorder is the leading cause of disability worldwide. Yet, there remain significant challenges in predicting new cases of major depression and devising strategies to prevent the disorder. An important first step in this process is identifying risk factors for the incidence of major depression. There is accumulating biological evidence linking insulin resistance, another highly prevalent condition, and depressive disorders. The objectives of this study were to examine whether three surrogate measures of insulin resistance (high triglyceride-HDL [high-density lipoprotein] ratio; prediabetes, as indicated by fasting plasma glucose level; and high central adiposity, as measured by waist circumference) at the time of study enrollment were associated with an increased rate of incident major depressive disorder over a 9-year follow-up period and to assess whether the new onset of these surrogate measures during the first 2 years after study enrollment was predictive of incident major depressive disorder during the subsequent follow-up period. Methods: The Netherlands Study of Depression and Anxiety (NESDA) is a multisite longitudinal study of the course and consequences of depressive and anxiety disorders in adults. The study population comprised 601 NESDA participants (18-65 years old) without a lifetime history of depression or anxiety disorders. The study's outcome was incident major depressive disorder, defined using DSM-IV criteria. Exposure measures included triglyceride-HDL ratio, fasting plasma glucose level, and waist circumference. Results: Fourteen percent of the sample developed major depressive disorder during follow-up. Cox proportional hazards models indicated that higher triglyceride-HDL ratio was positively associated with an increased risk for incident major depression (hazard ratio=1.89, 95% CI=1.15, 3.11), as were higher fasting plasma glucose levels (hazard ratio=1.37, 95% CI=1.05, 1.77) and higher waist circumference (hazard ratio=1.11 95% CI=1.01, 1.21). The development of prediabetes in the 2-year period after study enrollment was positively associated with incident major depressive disorder (hazard ratio=2.66, 95% CI=1.13, 6.27). The development of high triglyceride-HDL ratio and high central adiposity (cut-point >= 100 cm) in the same period was not associated with incident major depression. Conclusions: Three surrogate measures of insulin resistance positively predicted incident major depressive disorder in a 9-year follow-up period among adults with no history of depression or anxiety disorder. In addition, the development of prediabetes between enrollment and the 2-year study visit was positively associated with incident major depressive disorder. These findings may have utility for evaluating the risk for the development of major depression among patients with insulin resistance or metabolic pathology.
Zhang SY, Harschnitz O, Studer L, Casanova JL
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Neuron-intrinsic immunity to viruses in mice and humans (opens in new window)

CURRENT OPINION IN IMMUNOLOGY 2021 OCT; 72(?):309-317
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Viral encephalitis is a major neglected medical problem. Host defense mechanisms against viral infection of the central nervous system (CNS) have long remained unclear. The few previous studies of CNS-specific immunity to viruses in mice in vivo and humans in vitro have focused on the contributions of circulating leukocytes, resident microglial cells and astrocytes, with neurons long considered passive victims of viral infection requiring protection from extrinsic antiviral mechanisms. The last decade has witnessed the gradual emergence of the notion that neurons also combat viruses through cell-intrinsic mechanisms. Forward genetic approaches in humans have shown that monogenic inborn errors of TLR3, IFN-alpha/beta, or snoRNA31 immunity confer susceptibility to herpes simplex virus 1 (HSV-1) infection of the forebrain, whereas inborn errors of DBR1 underlie brainstem infections due to various viruses, including HSV-1. The study of human pluripotent stem cell (hPSC)-derived CNS-resident cells has unraveled known (i.e. TLR3-dependent IFN-alpha/beta immunity) and new (i.e. snoRNA31-dependent or DBR1-dependent immunity) cell-intrinsic antiviral mechanisms operating in neurons. Reverse genetic approaches in mice have confirmed that some known antiviral mechanisms also operate in mouse neurons (e.g. TLR3 and IFN-alpha/beta immunity). The search for human inborn errors of immunity (IEIs) underlying various forms of viral encephalitis, coupled with mouse models in vivo, and hPSC-based culture models of CNS and peripheral nervous system cells and organoids in vitro, should shed further light on the cell-specific and tissue-specific mechanisms of host defense against viruses in the human brain.