Increased anger and stress and heightened connectivity between IFG and vmPFC in victims during social interaction.

Self-identification as a victim of violence may lead to increased negative emotions and stress and thus, may change both structure and function of the underlying neural network(s). In a trans-diagnostic sample of individuals who identified themselves as victims of violence and a matched control group with no prior exposure to violence, we employed a social exclusion paradigm, the Cyberball task, to stimulate the re-experience of stress. Participants were partially excluded in the ball-tossing game without prior knowledge. We analyzed group differences in brain activity and functional connectivity during exclusion versus inclusion in exclusion-related regions. The victim group showed increased anger and stress levels during all conditions. Activation patterns during the task did not differ between groups but an enhanced functional connectivity between the IFG and the right vmPFC distinguished victims from controls during exclusion. This effect was driven by aberrant connectivity in victims during inclusion rather than exclusion, indicating that victimization affects emotional responses and inclusion-related brain connectivity rather than exclusion-related brain activity or connectivity. Victims may respond differently to the social context itself. Enhanced negative emotions and connectivity deviations during social inclusion may depict altered social processing and may thus affect social interactions.

A revised conceptual framework for mouse vomeronasal pumping and stimulus sampling.

The physiological performance of any sensory organ is determined by its anatomy and physical properties. Consequently, complex sensory structures with elaborate features have evolved to optimize stimulus detection. Understanding these structures and their physical nature forms the basis for mechanistic insights into sensory function. Despite its crucial role as a sensor for pheromones and other behaviorally instructive chemical cues, the vomeronasal organ (VNO) remains a poorly characterized mammalian sensory structure. Fundamental principles of its physico-mechanical function, including basic aspects of stimulus sampling, remain poorly explored. Here, we revisit the classical vasomotor pump hypothesis of vomeronasal stimulus uptake. Using advanced anatomical, histological, and physiological methods, we demonstrate that large parts of the lateral mouse VNO are composed of smooth muscle. Vomeronasal smooth muscle tissue comprises two subsets of fibers with distinct topography, structure, excitation-contraction coupling, and, ultimately, contractile properties. Specifically, contractions of a large population of noradrenaline-sensitive cells mediate both transverse and longitudinal lumen expansion, whereas cholinergic stimulation targets an adluminal group of smooth muscle fibers. The latter run parallel to the VNO's rostro-caudal axis and are ideally situated to mediate antagonistic longitudinal constriction of the lumen. This newly discovered arrangement implies a novel mode of function. Single-cell transcriptomics and pharmacological profiling reveal the receptor subtypes involved. Finally, 2D/3D tomography provides non-invasive insight into the intact VNO's anatomy and mechanics, enables measurement of luminal fluid volume, and allows an assessment of relative volume change upon noradrenergic stimulation. Together, we propose a revised conceptual framework for mouse vomeronasal pumping and, thus, stimulus sampling.

Reduced Gray Matter Volume and Cortical Thickness in Patients With Small-Fiber Neuropathy.

Small-fiber neuropathy (SFN) is defined by degeneration or dysfunction of peripheral sensory nerve endings. Central correlates have been identified on the level of gray matter volume (GMV) and cortical thickness (CT) changes. However, across SFN etiologies knowledge about a common structural brain signature is still lacking. Therefore, we recruited 26 SFN patients and 25 age- and sex-matched healthy controls to conduct voxel-based- and surface-based morphometry. Across all patients, we found reduced GMV in widespread frontal regions, left caudate, insula and superior parietal lobule. Surface-based morphometry analysis revealed reduced CT in the right precentral gyrus of SFN patients. In a region-based approach, patients had reduced GMV in the left caudate. Since pathogenic gain-of-function variants in voltage-gated sodium channels (Nav) have been associated with SFN pathophysiology, we explored brain morphological patterns in a homogenous subsample of patients carrying rare heterozygous missense variants. Whole brain- and region-based approaches revealed GMV reductions in the bilateral caudate for Nav variant carriers. Further research is needed to analyze the specific role of Nav variants for structural brain alterations. Together, we conclude that SFN patients have specific GMV and CT alterations, potentially forming potential new central biomarkers for this condition. Our results might help to better understand underlying or compensatory mechanisms of chronic pain perception in the future. PERSPECTIVE: This study reveals structural brain changes in small-fiber neuropathy (SFN) patients, particularly in frontal regions, caudate, insula, and parietal lobule. Notably, individuals with SFN and specific Nav variants exhibit bilateral caudate abnormalities. These findings may serve as potential central biomarkers for SFN and provide insights into chronic pain perception mechanisms.

Stimulus-Induced Theta-Band LFP Oscillations Format Neuronal Representations of Social Chemosignals in the Mouse Accessory Olfactory Bulb.

Social communication is crucial for the survival of many species. In most vertebrates, a dedicated chemosensory system, the vomeronasal system (VNS), evolved to process ethologically relevant chemosensory cues. The first central processing stage of the VNS is the accessory olfactory bulb (AOB), which sends information to downstream brain regions via AOB mitral cells (AMCs). Recent studies provided important insights about the functional properties of AMCs, but little is known about the principles that govern their coordinated activity. Here, we recorded local field potentials (LFPs) and single-unit activity in the AOB of adult male and female mice during presentation of natural stimuli. Our recordings reveal prominent LFP theta-band oscillatory episodes with a characteristic spatial pattern across the AOB. Throughout an experiment, the AOB network shows varying degrees of similarity to this pattern, in a manner that depends on the sensory stimulus. Analysis of LFP signal polarity and single-unit activity indicates that oscillatory episodes are generated locally within the AOB, likely representing a reciprocal interaction between AMCs and granule cells. Notably, spike times of many AMCs are constrained to the negative LFP oscillation phase in a manner that can drastically affect integration by downstream processing stages. Based on these observations, we propose that LFP oscillations may gate, bind, and organize outgoing signals from individual AOB neurons to downstream processing stages. Our findings suggest that, as in other neuronal systems and brain regions, population-level oscillations play a key role in organizing and enhancing transmission of socially relevant chemosensory information.SIGNIFICANCE STATEMENT The accessory olfactory bulb (AOB) is the first central stage of the vomeronasal system, a chemosensory system dedicated to processing cues from other organisms. Information from the AOB is conveyed to other brain regions via activity of its principal neurons, AOB mitral cells (AMCs). Here, we show that socially relevant sensory stimulation of the mouse vomeronasal system leads not only to changes in AMC activity, but also to distinct theta-band (∼5 Hz) oscillatory episodes in the local field potential. Notably AMCs favor the negative phase of these oscillatory events. Our findings suggest a novel mechanism for the temporal coordination of distributed patterns of neuronal activity, which can serve to efficiently activate downstream processing stages.

Systems neuroscience: A box full of tools to illuminate the black box of the brain.

Investigation of brain function has been fueled by an accelerating development of novel technologies and tools. This Perspective looks at the unprecedented neurotechnological progress of the past 2 decades and discusses future strategies to elucidate brain function.

The second PI(3,5)P2 binding site in the S0 helix of KCNQ1 stabilizes PIP2-at the primary PI1 site with potential consequences on intermediate-to-open state transition.

The Phosphatidylinositol 3-phosphate 5-kinase Type III PIKfyve is the main source for selectively generated phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), a known regulator of membrane protein trafficking. PI(3,5)P2 facilitates the cardiac KCNQ1/KCNE1 channel plasma membrane abundance and therewith increases the macroscopic current amplitude. Functional-physical interaction of PI(3,5)P2 with membrane proteins and its structural impact is not sufficiently understood. This study aimed to identify molecular interaction sites and stimulatory mechanisms of the KCNQ1/KCNE1 channel via the PIKfyve-PI(3,5)P2 axis. Mutational scanning at the intracellular membrane leaflet and nuclear magnetic resonance (NMR) spectroscopy identified two PI(3,5)P2 binding sites, the known PIP2 site PS1 and the newly identified N-terminal α-helix S0 as relevant for functional PIKfyve effects. Cd2+ coordination to engineered cysteines and molecular modeling suggest that repositioning of S0 stabilizes the channel s open state, an effect strictly dependent on parallel binding of PI(3,5)P2 to both sites.

Neural correlates of multisensory integration in the human brain: an ALE meta-analysis.

Previous fMRI research identified superior temporal sulcus as central integration area for audiovisual stimuli. However, less is known about a general multisensory integration network across senses. Therefore, we conducted activation likelihood estimation meta-analysis with multiple sensory modalities to identify a common brain network. We included 49 studies covering all Aristotelian senses i.e., auditory, visual, tactile, gustatory, and olfactory stimuli. Analysis revealed significant activation in bilateral superior temporal gyrus, middle temporal gyrus, thalamus, right insula, and left inferior frontal gyrus. We assume these regions to be part of a general multisensory integration network comprising different functional roles. Here, thalamus operate as first subcortical relay projecting sensory information to higher cortical integration centers in superior temporal gyrus/sulcus while conflict-processing brain regions as insula and inferior frontal gyrus facilitate integration of incongruent information. We additionally performed meta-analytic connectivity modelling and found each brain region showed co-activations within the identified multisensory integration network. Therefore, by including multiple sensory modalities in our meta-analysis the results may provide evidence for a common brain network that supports different functional roles for multisensory integration.

Fluoride Transport and Inhibition Across CLC Transporters.

The Chloride Channel (CLC) family includes proton-coupled chloride and fluoride transporters. Despite their similar protein architecture, the former exchange two chloride ions for each proton and are inhibited by fluoride, whereas the latter efficiently transport one fluoride in exchange for one proton. The combination of structural, mutagenesis, and functional experiments with molecular simulations has pinpointed several amino acid changes in the permeation pathway that capitalize on the different chemical properties of chloride and fluoride to fine-tune protein function. Here we summarize recent findings on fluoride inhibition and transport in the two prototypical members of the CLC family, the chloride/proton transporter from Escherichia coli (CLC-ec1) and the fluoride/proton transporter from Enterococcus casseliflavus (CLCF-eca).

Purinergic Signaling in Spermatogenesis.

Adenosine triphosphate (ATP) serves as the essential source of cellular energy. Over the last two decades, however, ATP has also attracted increasing interest as an extracellular signal that activates purinergic plasma membrane receptors of the P2 family. P2 receptors are divided into two types: ATP-gated nonselective cation channels (P2X) and G protein-coupled receptors (P2Y), the latter being activated by a broad range of purine and pyrimidine nucleotides (ATP, ADP, UTP, and UDP, among others). Purinergic signaling mechanisms are involved in numerous physiological events and pathophysiological conditions. Here, we address the growing body of evidence implicating purinergic signaling in male reproductive system functions. The life-long generation of fertile male germ cells is a highly complex, yet mechanistically poorly understood process. Given the relatively sparse innervation of the testis, spermatogenesis relies on both endocrine control and multi-directional paracrine communication. Therefore, a detailed understanding of such paracrine messengers, including ATP, is crucial to gain mechanistic insight into male reproduction.⁠.

Sparser and Less Efficient Hippocampal-Prefrontal Projections account for Developmental Network Dysfunction in a Model of Psychiatric Risk Mediated by Gene-Environment Interaction.

Precise information flow from the hippocampus (HP) to prefrontal cortex (PFC) emerges during early development and accounts for cognitive processing throughout life. On flip side, this flow is selectively impaired in mental illness. In mouse models of psychiatric risk mediated by gene-environment interaction (GE), the prefrontal-hippocampal coupling is disrupted already shortly after birth. While this impairment relates to local miswiring in PFC and HP, it might be also because of abnormal connectivity between the two brain areas. Here, we test this hypothesis by combining in vivo electrophysiology and optogenetics with in-depth tracing of projections and monitor the morphology and function of hippocampal afferents in the PFC of control and GE mice of either sex throughout development. We show that projections from the hippocampal CA1 area preferentially target layer 5/6 pyramidal neurons and interneurons, and to a lesser extent layer 2/3 neurons of prelimbic cortex (PL), a subdivision of PFC. In neonatal GE mice, sparser axonal projections from CA1 pyramidal neurons with decreased release probability reach the PL. Their ability to entrain layer 5/6 oscillatory activity and firing is decreased. These structural and functional deficits of hippocampal-prelimbic connectivity persist, yet are less prominent in prejuvenile GE mice. Thus, besides local dysfunction of HP and PL, weaker connectivity between the two brain areas is present in GE mice throughout development.SIGNIFICANCE STATEMENT Poor cognitive performance in mental disorders comes along with prefrontal-hippocampal dysfunction. Recent data from mice that model the psychiatric risk mediated by gene-environment (GE) interaction identified the origin of deficits during early development, when the local circuits in both areas are compromised. Here, we show that sparser and less efficient connectivity as well as cellular dysfunction are the substrate of the weaker excitatory drive from hippocampus (HP) to prefrontal cortex (PFC) as well as of poorer oscillatory coupling between the two brain areas in these mice. While the structural and functional connectivity deficits persist during the entire development, their magnitude decreases with age. The results add experimental evidence for the developmental miswiring hypothesis of psychiatric disorders.

Ventral striatal islands of Calleja neurons control grooming in mice.

The striatum comprises multiple subdivisions and neural circuits that differentially control motor output. The islands of Calleja (IC) contain clusters of densely packed granule cells situated in the ventral striatum, predominantly in the olfactory tubercle (OT). Characterized by expression of the D3 dopamine receptor, the IC are evolutionally conserved, but have undefined functions. Here, we show that optogenetic activation of OT D3 neurons robustly initiates self-grooming in mice while suppressing other ongoing behaviors. Conversely, optogenetic inhibition of these neurons halts ongoing grooming, and genetic ablation reduces spontaneous grooming. Furthermore, OT D3 neurons show increased activity before and during grooming and influence local striatal output via synaptic connections with neighboring OT neurons (primarily spiny projection neurons), whose firing rates display grooming-related modulation. Our study uncovers a new role of the ventral striatum's IC in regulating motor output and has important implications for the neural control of grooming.

TMEM16A and TMEM16B Modulate Pheromone-Evoked Action Potential Firing in Mouse Vomeronasal Sensory Neurons.

The mouse vomeronasal system controls several social behaviors. Pheromones and other social cues are detected by sensory neurons in the vomeronasal organ (VNO). Stimuli activate a transduction cascade that leads to membrane potential depolarization, increase in cytosolic Ca2+ level, and increased firing. The Ca2+-activated chloride channels TMEM16A and TMEM16B are co-expressed within microvilli of vomeronasal neurons, but their physiological role remains elusive. Here, we investigate the contribution of each of these channels to vomeronasal neuron firing activity by comparing wild-type (WT) and knock-out (KO) mice. Performing loose-patch recordings from neurons in acute VNO slices, we show that spontaneous activity is modified by Tmem16a KO, indicating that TMEM16A, but not TMEM16B, is active under basal conditions. Upon exposure to diluted urine, a rich source of mouse pheromones, we observe significant changes in activity. Vomeronasal sensory neurons (VSNs) from Tmem16a cKO and Tmem16b KO mice show shorter interspike intervals (ISIs) compared with WT mice, indicating that both TMEM16A and TMEM16B modulate the firing pattern of pheromone-evoked activity in VSNs.

The Potential Effect of Na v 1.8 in Autism Spectrum Disorder: Evidence From a Congenital Case With Compound Heterozygous SCN10A Mutations.

Apart from the most prominent symptoms in Autism spectrum disorder (ASD), namely deficits in social interaction, communication and repetitive behavior, patients often show abnormal sensory reactivity to environmental stimuli. Especially potentially painful stimuli are reported to be experienced in a different way compared to healthy persons. In our present study, we identified an ASD patient carrying compound heterozygous mutations in the voltage-gated sodium channel (VGSC) Na v 1.8, which is preferentially expressed in sensory neurons. We expressed both mutations, p.I1511M and p.R512∗, in a heterologous expression system and investigated their biophysical properties using patch-clamp recordings. The results of these experiments reveal that the p.R512∗ mutation renders the channel non-functional, while the p.I1511M mutation showed only minor effects on the channel's function. Behavioral experiments in a Na v 1.8 loss-of-function mouse model additionally revealed that Na v 1.8 may play a role in autism-like symptomatology. Our results present Na v 1.8 as a protein potentially involved in ASD pathophysiology and may therefore offer new insights into the genetic basis of this disease.

Do all mice smell the same? Chemosensory cues from inbred and wild mouse strains elicit stereotypic sensory representations in the accessory olfactory bulb.

BACKGROUND: For many animals, chemosensory cues are vital for social and defensive interactions and are primarily detected and processed by the vomeronasal system (VNS). These cues are often inherently associated with ethological meaning, leading to stereotyped behaviors. Thus, one would expect consistent representation of these stimuli across different individuals. However, individuals may express different arrays of vomeronasal sensory receptors and may vary in the pattern of connections between those receptors and projection neurons in the accessory olfactory bulb (AOB). In the first part of this study, we address the ability of individuals to form consistent representations despite these potential sources of variability. The second part of our study is motivated by the fact that the majority of research on VNS physiology involves the use of stimuli derived from inbred animals. Yet, it is unclear whether neuronal representations of inbred-derived stimuli are similar to those of more ethologically relevant wild-derived stimuli. RESULTS: First, we compared sensory representations to inbred, wild-derived, and wild urine stimuli in the AOBs of males from two distinct inbred strains, using them as proxies for individuals. We found a remarkable similarity in stimulus representations across the two strains. Next, we compared AOB neuronal responses to inbred, wild-derived, and wild stimuli, again using male inbred mice as subjects. Employing various measures of neuronal activity, we show that wild-derived and wild stimuli elicit responses that are broadly similar to those from inbred stimuli: they are not considerably stronger or weaker, they show similar levels of sexual dimorphism, and when examining population-level activity, cluster with inbred mouse stimuli. CONCLUSIONS: Despite strain-specific differences and apparently random connectivity, the AOB can maintain stereotypic sensory representations for broad stimulus categories, providing a substrate for common stereotypical behaviors. In addition, despite many generations of inbreeding, AOB representations capture the key ethological features (i.e., species and sex) of wild-derived and wild counterparts. Beyond these broad similarities, representations of stimuli from wild mice are nevertheless distinct from those elicited by inbred mouse stimuli, suggesting that laboratory inbreeding has indeed resulted in marked modifications of urinary secretions.

Testicular adenosine acts as a pro-inflammatory molecule: role of testicular peritubular cells.

Extracellular ATP has been described to be involved in inflammatory cytokine production by human testicular peritubular cells (HTPCs). The ectonucleotidases ENTPD1 and NT5E degrade ATP and have been reported in rodent testicular peritubular cells. We hypothesized that if a similar situation exists in human testis, ATP metabolites may contribute to cytokine production. Indeed, ENTPD1 and NT5E were found in situ and in vitro in HTPCs. Malachite green assays confirmed enzyme activities in HTPCs. Pharmacological inhibition of ENTPD1 (by POM-1) significantly reduced pro-inflammatory cytokines evoked by ATP treatment, suggesting that metabolites of ATP, including adenosine, are likely involved. We focused on adenosine and detected three of the four known adenosine receptors in HTPCs. One, A2B, was also found in situ in peritubular cells of human testicular sections. The A2B agonist BAY60-6583 significantly elevated levels of IL6 and CXCL8, a result also obtained with adenosine and its analogue NECA. Results of siRNA-mediated A2B down-regulation support a role of this receptor. In mouse peritubular cells, in contrast to HTPCs, all four of the known adenosine receptors were detected; when challenged with adenosine, cytokine expression levels significantly increased. Organotypic short-term testis cultures yielded comparable results and indicate an overall pro-inflammatory action of adenosine in the mouse testis. If transferable to the in vivo situation, our results may implicate that interference with the generation of ATP metabolites or interference with adenosine receptors could reduce inflammatory events in the testis. These novel insights may provide new avenues for treatment of sterile inflammation in male subfertility and infertility.

DNA Methyltransferase 1 (DNMT1) Shapes Neuronal Activity of Human iPSC-Derived Glutamatergic Cortical Neurons.

Epigenetic mechanisms are emerging key players for the regulation of brain function, synaptic activity, and the formation of neuronal engrams in health and disease. As one important epigenetic mechanism of transcriptional control, DNA methylation was reported to distinctively modulate synaptic activity in excitatory and inhibitory cortical neurons in mice. Since DNA methylation signatures are responsive to neuronal activity, DNA methylation seems to contribute to the neuron's capacity to adapt to and integrate changing activity patterns, being crucial for the plasticity and functionality of neuronal circuits. Since most studies addressing the role of DNA methylation in the regulation of synaptic function were conducted in mice or murine neurons, we here asked whether this functional implication applies to human neurons as well. To this end, we performed calcium imaging in human induced pluripotent stem cell (iPSC)-derived excitatory cortical neurons forming synaptic contacts and neuronal networks in vitro. Treatment with DNMT1 siRNA that diminishs the expression of the DNA (cytosine-5)-methyltransferase 1 (DNMT1) was conducted to investigate the functional relevance of DNMT1 as one of the main enzymes executing DNA methylations in the context of neuronal activity modulation. We observed a lowered proportion of actively firing neurons upon DNMT1-knockdown in these iPSC-derived excitatory neurons, pointing to a correlation of DNMT1-activity and synaptic transmission. Thus, our experiments suggest that DNMT1 decreases synaptic activity of human glutamatergic neurons and underline the relevance of epigenetic regulation of synaptic function also in human excitatory neurons.

ATP activation of peritubular cells drives testicular sperm transport.

Spermatogenesis, the complex process of male germ cell proliferation, differentiation, and maturation, is the basis of male fertility. In the seminiferous tubules of the testes, spermatozoa are constantly generated from spermatogonial stem cells through a stereotyped sequence of mitotic and meiotic divisions. The basic physiological principles, however, that control both maturation and luminal transport of the still immotile spermatozoa within the seminiferous tubules remain poorly, if at all, defined. Here, we show that coordinated contractions of smooth muscle-like testicular peritubular cells provide the propulsive force for luminal sperm transport toward the rete testis. Using a mouse model for in vivo imaging, we describe and quantify spontaneous tubular contractions and show a causal relationship between peritubular Ca2+ waves and peristaltic transport. Moreover, we identify P2 receptor-dependent purinergic signaling pathways as physiological triggers of tubular contractions both in vitro and in vivo. When challenged with extracellular ATP, transport of luminal content inside the seminiferous tubules displays stage-dependent directionality. We thus suggest that paracrine purinergic signaling coordinates peristaltic recurrent contractions of the mouse seminiferous tubules to propel immotile spermatozoa to the rete testis.

As sperm develop in the testis, the immature cells must make their way through a maze of small tubes known as seminiferous tubules. However, at this stage, the cells do not yet move the long tails that normally allow them to 'swim'; it is therefore unclear how they are able to move through the tubules. Now, Fleck, Kenzler et al. have showed that, in mice, muscle-like cells within the walls of seminiferous tubules can create waves of contractions that push sperm along. Further experiments were then conducted on cells grown in the laboratory. This revealed that a signaling molecule called ATP orchestrates the moving process by activating a cascade of molecular events that result in contractions. Fleck, Kenzler et al. then harnessed an advanced microscopy technique to demonstrate that this mechanism occurs in living mice. Together, these results provide a better understanding of how sperm mature, which could potentially be relevant for both male infertility and birth control.

Bursting mitral cells time the oscillatory coupling between olfactory bulb and entorhinal networks in neonatal mice.

KEY POINTS: During early postnatal development, mitral cells show either irregular bursting or non-bursting firing patterns Bursting mitral cells preferentially fire during theta bursts in the neonatal olfactory bulb, being locked to the theta phase Bursting mitral cells preferentially fire during theta bursts in the neonatal lateral entorhinal cortex and are temporally related to both respiration rhythm- and theta phase Bursting mitral cells act as a cellular substrate of the olfactory drive that promotes the oscillatory entrainment of entorhinal networks ABSTRACT: Shortly after birth, the olfactory system provides not only the main source of environmental inputs to blind, deaf, non-whisking and motorically-limited rodents, but also the drive boosting the functional entrainment of limbic circuits. However, the cellular substrate of this early communication remains largely unknown. Here, we combine in vivo and in vitro patch-clamp and extracellular recordings to reveal the contribution of mitral cell (MC) firing to early patterns of network activity in both the neonatal olfactory bulb (OB) and the lateral entorhinal cortex (LEC), the gatekeeper of limbic circuits. We show that MCs predominantly fire either in an irregular bursting or non-bursting pattern during discontinuous theta events in the OB. However, the temporal spike-theta phase coupling is stronger for bursting than non-bursting MCs. In line with the direct OB-to-LEC projections, both bursting and non-bursting discharge augments during co-ordinated patterns of entorhinal activity, albeit with higher magnitude for bursting MCs. For these neurons, temporal coupling to the discontinuous theta events in the LEC is stronger. Thus, bursting MCs might drive the entrainment of the OB-LEC network during neonatal development.