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Precise neuromodulation is critical for interrogating cellular communication and treating neurological diseases. Nanoscale transducers have emerged as effective interfaces to exert photothermal effects and modulate neural activities with a high spatiotemporal resolution. Ideal materials for this application should possess strong light absorption, high photothermal conversion efficiency, and great biocompatibility for clinical translation. Here, we show that the structurally designed 3D Au superparticles with a highly branched morphology can be promising candidates for nongenetic and remote neuromodulation. The structure-induced blackbody-like absorption endows Au superparticles with photothermal conversion efficiency over 90%, much higher than that of conventional Au nanorods. With the biocompatible polydopamine ligands, Au superparticles can be readily interfaced with primary mouse hippocampal neurons and other cells and can photostimulate or inhibit their activities in both cell networks or with a single-cell resolution. These findings highlight the importance of structural designs as powerful tools to promote the performance of plasmonic materials in neuromodulation and related research of neuroscience and neuroengineering.

Spatial information is encoded by location-dependent hippocampal place cell firing rates and sub-second, rhythmic entrainment of spike times. These rate and temporal codes have primarily been characterized in low-dimensional environments under limited cognitive demands; but how is coding configured in complex environments when individual place cells signal several locations, individual locations contribute to multiple routes and functional demands vary? Quantifying CA1 population dynamics of male rats during a decision-making task, here we show that the phase of individual place cells' spikes relative to the local theta rhythm shifts to differentiate activity in different place fields. Theta phase coding also disambiguates repeated visits to the same location during different routes, particularly preceding spatial decisions. Using unsupervised detection of cell assemblies alongside theoretical simulation, we show that integrating rate and phase coding mechanisms dynamically recruits units to different assemblies, generating spiking sequences that disambiguate episodes of experience and multiplexing spatial information with cognitive context., (© 2024. The Author(s).)

Capacitance of biological membranes is determined by the properties of the lipid portion of the membrane as well as the morphological features of a cell. In neurons, membrane capacitance is a determining factor of synaptic integration, action potential propagation speed, and firing frequency due to its direct effect on the membrane time constant. Besides slow changes associated with increased morphological complexity during postnatal maturation, neuronal membrane capacitance is considered a stable, non-regulated, and constant magnitude. Here we report that, in two excitatory neuronal cell types, pyramidal cells of the mouse primary visual cortex and granule cells of the hippocampus, the membrane capacitance significantly changes between the start and the end of a daily light-dark cycle. The changes are large, nearly 2-fold in magnitude in pyramidal cells, but are not observed in cortical parvalbumin-expressing inhibitory interneurons. Consistent with daily capacitance fluctuations, the time window for synaptic integration also changes in pyramidal cells., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The formation, stabilization, and elimination of synapses are tightly regulated during neural development and into adulthood. Pumilio RNA-binding proteins regulate the translation and localization of many synaptic mRNAs and are developmentally downregulated in the brain. We found that simultaneous downregulation of Pumilio 1 and 2 increases both excitatory and inhibitory synapse density in primary hippocampal neurons and promotes synapse maturation. Loss of Pum1 and Pum2 in the mouse brain was associated with an increase in mRNAs involved in mitochondrial function and synaptic translation. These findings reveal a role for developmental Pumilio downregulation as a permissive step in the maturation of synapses and suggest that modulation of Pumilio levels is a cell-intrinsic mechanism by which neurons tune their capacity for synapse stabilization., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The orbitofrontal cortex (OFC) and hippocampus (HC) both contribute to the cognitive maps that support flexible behavior. Previously, we used the dopamine neurons to measure the functional role of OFC. We recorded midbrain dopamine neurons as rats performed an odor-based choice task, in which expected rewards were manipulated across blocks. We found that ipsilateral OFC lesions degraded dopaminergic prediction errors, consistent with reduced resolution of the task states. Here we have repeated this experiment in male rats with ipsilateral HC lesions. The results show HC also shapes the task states, however unlike OFC, which provides information local to the trial, the HC is necessary for estimating upper-level hidden states that distinguish blocks. The results contrast the roles of the OFC and HC in cognitive mapping and suggest that the dopamine neurons access rich information from distributed regions regarding the environment's structure, potentially enabling this teaching signal to support complex behaviors., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Exocytosis is a fundamental process used by eukaryotes to regulate the composition of the plasma membrane and facilitate cell-cell communication. To investigate exocytosis in neuronal morphogenesis, previously we developed computational tools with a graphical user interface to enable the automatic detection and analysis of exocytic events from fluorescence timelapse images. Although these tools were useful, we found the code was brittle and not easily adapted to different experimental conditions. Here, we developed and validated a robust and versatile toolkit, named pHusion, for the analysis of exocytosis, written in ImageTank, a graphical programming language that combines image visualization and numerical methods. We tested pHusion using a variety of imaging modalities and pH-sensitive fluorophores, diverse cell types and various exocytic markers, to generate a flexible and intuitive package. Using this system, we show that VAMP3-mediated exocytosis occurs 30-times more frequently in melanoma cells compared with primary oligodendrocytes, that VAMP2-mediated fusion events in mature rat hippocampal neurons are longer lasting than those in immature murine cortical neurons, and that exocytic events are clustered in space yet random in time in developing cortical neurons., Competing Interests: Competing interests D.A. is the owner of Visual Data Tools Inc. developer of ImageTank and DataGraph., (© 2024. Published by The Company of Biologists Ltd.)

α-Neurexins are essential and highly expressed presynaptic cell-adhesion molecules that are frequently linked to neuropsychiatric and neurodevelopmental disorders. Despite their importance, how the elaborate extracellular sequences of α-neurexins contribute to synapse function is poorly understood. We recently characterized the presynaptic gain-of-function phenotype caused by a missense mutation in an evolutionarily conserved extracellular sequence of neurexin-3α (A687T) that we identified in a patient diagnosed with profound intellectual disability and epilepsy. The striking A687T gain-of-function mutation on neurexin-3α prompted us to systematically test using mutants whether the presynaptic gain-of-function phenotype is a consequence of the addition of side-chain bulk (i.e., A687V) or polar/hydrophilic properties (i.e., A687S). We used multidisciplinary approaches in mixed-sex primary hippocampal cultures to assess the impact of the neurexin-3α A687 residue on synapse morphology, function and ligand binding. Unexpectedly, neither A687V nor A687S recapitulated the neurexin-3α A687T phenotype. Instead, distinct from A687T, molecular replacement with A687S significantly enhanced postsynaptic properties exclusively at excitatory synapses and selectively increased binding to neuroligin-1 and neuroligin-3 without changing binding to neuroligin-2 or LRRTM2. Importantly, we provide the first experimental evidence supporting the notion that the position A687 of neurexin-3α and the N-terminal sequences of neuroligins may contribute to the stability of α-neurexin-neuroligin-1 trans-synaptic interactions and that these interactions may specifically regulate the postsynaptic strength of excitatory synapses., Competing Interests: The authors declare no competing financial interests., (Copyright © 2024 the authors.)

Olfaction is a fundamental sensory modality that guides animal and human behaviour 1,2 . However, the underlying neural processes of human olfaction are still poorly understood at the fundamental-that is, the single-neuron-level. Here we report recordings of single-neuron activity in the piriform cortex and medial temporal lobe in awake humans performing an odour rating and identification task. We identified odour-modulated neurons within the piriform cortex, amygdala, entorhinal cortex and hippocampus. In each of these regions, neuronal firing accurately encodes odour identity. Notably, repeated odour presentations reduce response firing rates, demonstrating central repetition suppression and habituation. Different medial temporal lobe regions have distinct roles in odour processing, with amygdala neurons encoding subjective odour valence, and hippocampal neurons predicting behavioural odour identification performance. Whereas piriform neurons preferably encode chemical odour identity, hippocampal activity reflects subjective odour perception. Critically, we identify that piriform cortex neurons reliably encode odour-related images, supporting a multimodal role of the human piriform cortex. We also observe marked cross-modal coding of both odours and images, especially in the amygdala and piriform cortex. Moreover, we identify neurons that respond to semantically coherent odour and image information, demonstrating conceptual coding schemes in olfaction. Our results bridge the long-standing gap between animal models and non-invasive human studies and advance our understanding of odour processing in the human brain by identifying neuronal odour-coding principles, regional functional differences and cross-modal integration., (© 2024. The Author(s).)

The Preyssler-type polyoxotungstate ({P 5 W 30 }) belongs to the family of polyanionic metal-oxides formed by group V and VI metal ions, such as V, Mo and W, commonly known as polyoxometalates (POMs). POMs have demonstrated inhibitory effect on a significant number of ATP-binding proteins in vitro. Purinergic P2 receptors, widely expressed in eukaryotic cells, contain extracellularly oriented ATP-binding sites and play many biological roles with health implications. In this work, we use the immortalized mouse hippocampal neuronal HT-22 cells in culture to study the effects of {P 5 W 30 } on the cytosolic Ca 2+ concentration. Changes in cytosolic Ca 2+ concentration were monitored using fluorescence microscopy of HT-22 cells loaded with the fluorescent Ca 2+ indicator Fluo3. 31 P-Nuclear magnetic resonance measurements of {P 5 W 30 } indicate its stability in the medium used for cytosolic Ca 2+ measurements for over 30 min. The findings reveal that addition of {P 5 W 30 } to the extracellular medium induces a sustained increase of the cytosolic Ca 2+ concentration within minutes. This Ca 2+ increase is triggered by extracellular Ca 2+ entry into the cells and is dose-dependent, with a half-of-effect concentration of 0.25 ± 0.05 μM {P 5 W 30 }. In addition, after the {P 5 W 30 }-induced cytosolic Ca 2+ increase, the transient Ca 2+ peak induced by extracellular ATP is reduced up to 100% with an apparent half-of-effect concentration of 0.15 ± 0.05 μM {P 5 W 30 }. Activation of metabotropic purinergic P2 receptors affords about 80% contribution to the increase of Fluo3 fluorescence elicited by {P 5 W 30 } in HT-22 cells, whereas ionotropic receptors contribute, at most, with 20%. These results suggest that {P 5 W 30 } could serve as a novel agonist of purinergic P2 receptors., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Annette Rompel, Nadiia I. Gumerova reports financial support was provided by Austrian Science Fund. Manuel Aureliano reports financial support was provided by Foundation for Science and Technology. Carlos Gutierrez-Merino, Ana M. Mata reports financial support was provided by Spanish State Research Agency. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Postnatal hippocampal neurogenesis is essential for learning and memory. Hippocampal neural precursor cells (NPCs) can be induced to proliferate and differentiate into either glial cells or dentate granule cells. Notably, hippocampal neurogenesis decreases dramatically with age, partly due to a reduction in the NPC pool and a decrease in their proliferative activity. Alpha-melanocyte-stimulating hormone (α-MSH) improves learning, memory, neuronal survival and plasticity. Here, we used postnatally-isolated hippocampal NPCs from Wistar rat pups (male and female combined) to determine the role of the melanocortin analog [Nle 4 , D-Phe 7 ]-α-MSH (NDP-MSH) in proliferation and fate acquisition of NPCs. Incubation of growth-factor deprived NPCs with 10 nM NDP-MSH for 6 days increased the proportion of Ki-67- and 5-bromo-2'-deoxyuridine (BrdU)-positive cells, compared to the control group, and these effects were blocked by the MC4R antagonist JKC-363. NDP-MSH also increased the proportion of glial fibrillar acidic protein (GFAP)/Ki-67, GFAP/sex-determining region Y-box2 (SOX2) and neuroepithelial stem cell protein (NESTIN)/Ki-67-double positive cells (type-1 and type-2 precursors). Finally, NDP-MSH induced peroxisome proliferator-activated receptor (PPAR)-γ protein expression, and co-incubation with the PPAR-γ inhibitor GW9662 prevented the effect of NDP-MSH on NPC proliferation and differentiation. Our results indicate that in vitro activation of MC4R in growth-factor-deprived postnatal hippocampal NPCs induces proliferation and promotes the relative expansion of the type-1 and type-2 NPC pool through a PPAR-γ-dependent mechanism. These results shed new light on the mechanisms underlying the beneficial effects of melanocortins in hippocampal plasticity and provide evidence linking the MC4R and PPAR-γ pathways in modulation of hippocampal NPC proliferation and differentiation., Competing Interests: Declaration of competing interest None., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Euclidean space is the fabric of the world we live in. Whether and how geometric experience shapes our spatial-temporal representations of the world remained unknown. We deprived male rats of experience with crucial features of Euclidean geometry by rearing them inside spheres, and compared activity of large hippocampal neuronal ensembles during navigation and sleep with that of cuboid cage-reared controls. Sphere-rearing from birth permitted emergence of accurate neuronal ensemble spatial codes and preconfigured and plastic time-compressed neuronal sequences. However, sphere-rearing led to diminished individual place cell tuning, more similar neuronal mapping of different track ends/corners, and impaired pattern separation and plasticity of multiple linear tracks, coupled with reduced preconfigured sleep network repertoires. Subsequent experience with multiple linear environments over four days largely reversed these effects. Thus, early-life experience with Euclidean geometry enriches the hippocampal repertoire of preconfigured neuronal patterns selected toward unique representation and discrimination of multiple linear environments., (© 2024. The Author(s).)

Microglia are resident immune cells in the brain that interact with neurons to maintain the homeostasis of the central nervous system (CNS). Studies show that the microglial surface expresses potassium channels that regulate microglial activation, while abnormalities in these potassium channels can lead to neural diseases. Currently, whole-cell patch-clamp recordings of microglia are mostly performed on cultured primary microglia from fetal or newborn mice due to difficulties in conducting electrophysiological evaluations on acutely isolated microglia. This study introduces an easy-to-follow protocol for isolating hippocampal microglia from adult mice and performing whole-cell patch-clamp recordings on the isolated cells. Briefly, the brain was removed from a mouse after decapitation, the hippocampus was dissected bilaterally, and microglia were isolated using an adult mouse brain dissociation kit. The microglia were then purified using a magnetic-activated cell sorting (MACS) method and seeded onto coverslips. Successful microglial isolation was confirmed by immunofluorescent staining with anti-CD11 and anti-Iba1 antibodies. A cover slip was placed in a recording chamber, and the whole-cell potassium currents of the acutely isolated microglia were recorded under voltage-clamp conditions.

Posttranslational modifications (PTMs) of tubulin, termed the "tubulin code", play important roles in regulating microtubule functions within subcellular compartments for specialized cellular activities. While numerous tubulin PTMs have been identified, a comprehensive understanding of the complete repertoire is still underway. In this study, we report that α-tubulin lactylation is catalyzed by HDAC6 by using lactate to increase microtubule dynamics in neurons. We identify lactylation on lysine 40 of α-tubulin in the soluble tubulin dimers. Notably, lactylated α-tubulin enhances microtubule dynamics and facilitates neurite outgrowth and branching in cultured hippocampal neurons. Moreover, we discover an unexpected function of HDAC6, acting as the primary lactyltransferase to catalyze α-tubulin lactylation. HDAC6-catalyzed lactylation is a reversible process, dependent on lactate concentrations. Intracellular lactate concentration triggers HDAC6 to lactylate α-tubulin, a process dependent on its deacetylase activity. Additionally, the lactyltransferase activity may be conserved in HDAC family proteins. Our study reveals the primary role of HDAC6 in regulating α-tubulin lactylation, establishing a link between cell metabolism and cytoskeleton functions., (© 2024. The Author(s).)

During discourse comprehension, every new word adds to an evolving representation of meaning that accumulates over consecutive sentences and constrains the next words. To minimize repetition and utterance length, languages use pronouns, like the word "she," to refer to nouns and phrases that were previously introduced. It has been suggested that language comprehension requires that pronouns activate the same neuronal representations as the nouns themselves. We recorded from individual neurons in the human hippocampus during a reading task. Cells that were selective to a particular noun were later reactivated by pronouns that refer to the cells' preferred noun. These results imply that concept cells contribute to a rapid and dynamic semantic memory network that is recruited during language comprehension.

Representation of the environment by hippocampal populations is known to drift even within a familiar environment, which could reflect gradual changes in single-cell activity or result from averaging across discrete switches of single neurons. Disambiguating these possibilities is crucial, as they each imply distinct mechanisms. Leveraging change point detection and model comparison, we find that CA1 population vectors decorrelate gradually within a session. In contrast, individual neurons exhibit predominantly step-like emergence and disappearance of place fields or sustained changes in within-field firing. The changes are not restricted to particular parts of the maze or trials and do not require apparent behavioral changes. The same place fields emerge, disappear, and reappear across days, suggesting that the hippocampus reuses pre-existing assemblies, rather than forming new fields de novo. Our results suggest an internally driven perpetual step-like reorganization of the neuronal assemblies., Competing Interests: Declaration of interests G.B. is a member of the advisory board of Neuron., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The brain can be seen as a self-organized dynamical system that optimizes information processing and storage capabilities. This is supported by studies across scales, from small neuronal assemblies to the whole brain, where neuronal activity exhibits features typically associated with phase transitions in statistical physics. Such a critical state is characterized by the emergence of scale-free statistics as captured, for example, by the sizes and durations of activity avalanches corresponding to a cascading process of information flow. Another phenomenon observed during sleep, under anesthesia, and in in vitro cultures, is that cortical and hippocampal neuronal networks alternate between "up" and "down" states characterized by very distinct firing rates. Previous theoretical work has been able to relate these two concepts and proposed that only up states are critical whereas down states are subcritical, also indicating that the brain spontaneously transitions between the two. Using high-speed high-resolution calcium imaging recordings of neuronal cultures, we test this hypothesis here by analyzing the neuronal avalanche statistics in populations of thousands of neurons during "up" and "down" states separately. We find that both "up" and "down" states can exhibit scale-free behavior when taking into account their intrinsic time scales. In particular, the statistical signature of "down" states is indistinguishable from those observed previously in cultures without "up" states. We show that such behavior can not be explained by network models of non-conservative leaky integrate-and-fire neurons with short-term synaptic depression, even when realistic noise levels, spatial network embeddings, and heterogeneous populations are taken into account, which instead exhibits behavior consistent with previous theoretical models. Similar differences were also observed when taking into consideration finite-size scaling effects, suggesting that the intrinsic dynamics and self-organization mechanisms of these cultures might be more complex than previously thought. In particular, our findings point to the existence of different mechanisms of neuronal communication, with different time scales, acting during either high-activity or low-activity states, potentially requiring different plasticity mechanisms., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yaghoubi, Orlandi, Colicos and Davidsen.)

Our brains create new memories by capturing the 'who/what', 'where' and 'when' of everyday experiences. On a neuronal level, mechanisms facilitating a successful transfer into episodic memory are still unclear. We investigated this by measuring single neuron activity in the human medial temporal lobe during encoding of item-location associations. While previous research has found predictive effects in population activity in human MTL structures, we could attribute such effects to two specialized sub-groups of neurons: concept cells in the hippocampus, amygdala and entorhinal cortex (EC), and a second group of parahippocampal location-selective neurons. In both item- and location-selective populations, firing rates were significantly higher during successfully encoded trials. These findings are in line with theories of hippocampal indexing, since selective index neurons may act as pointers to neocortical representations. Overall, activation of distinct populations of neurons could directly support the connection of the 'what' and 'where' of episodic memory., (© 2024. The Author(s).)

Fructose 1,6-bisphosphatase 2 (Fbp2) is a regulatory enzyme of gluco- and glyconeogenesis which, in the course of evolution, acquired non-catalytic functions. Fbp2 promotes cell survival during calcium stress, regulates glycolysis via inhibition of Hif-1α activity, and is indispensable for the formation of long-term potentiation in hippocampus. In hippocampal astrocytes, the amount of Fbp2 protein is reduced by signals delivered in neuronal extracellular vesicles (NEVs) through an unknown mechanism. The physiological role of Fbp2 (determined by its subcellular localization/interactions) depends on its oligomeric state and thus, we asked whether the cargo of NEVs is sufficient to change also the ratio of Fbp2 dimer/tetramer and, consequently, influence astrocyte basal metabolism. We found that the NEVs cargo reduced the Fbp2 mRNA level, stimulated the enzyme degradation and affected the cellular titers of different oligomeric forms of Fbp2. This was accompanied with increased glucose uptake and lactate release by astrocytes. Our results revealed that neuronal signals delivered to astrocytes in NEVs provide the necessary balance between enzymatic and non-enzymatic functions of Fbp2, influencing not only its amount but also subcellular localization. This may allow for the metabolic adjustments and ensure protection of mitochondrial membrane potential during the neuronal activity-related increase in astrocytic [Ca 2+ ]., (© 2024. The Author(s).)

We present here a view of the firing patterns of hippocampal cells that is contrary, both functionally and anatomically, to conventional wisdom. We argue that the hippocampus responds to efference copies of goals encoded elsewhere; and that it uses these to detect and resolve conflict or interference between goals in general. While goals can involve space, hippocampal cells do not encode spatial (or other special types of) memory, as such. We also argue that the transverse circuits of the hippocampus operate in an essentially homogeneous way along its length. The apparently different functions of different parts (e.g. memory retrieval versus anxiety) result from the different (situational/motivational) inputs on which those parts perform the same fundamental computational operations. On this view, the key role of the hippocampus is the iterative adjustment, via Papez-like circuits, of synaptic weights in cell assemblies elsewhere., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest to declare., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Sevoflurane (Sev) is a commonly used inhalation anaesthetic that has been shown to cause hippocampus dysfunction through multiple underlying molecular processes, including mitochondrial malfunction, oxidative stress and inflammation. Dihydromyricetin (DHM) is a 2,3-dihydroflavonoid with various biological properties, such as anti-inflammation and anti-oxidative stress. The purpose of this study was to investigate the effect of DHM on Sev-induced neuronal dysfunction. HT22 cells were incubated with 10, 20 and 30 μM of DHM for 24 h, and then stimulated with 4% Sev for 6 h. The effects and mechanism of DHM on inflammation, oxidative stress and mitochondrial dysfunction were explored in Sev-induced HT22 cells by Cell Counting Kit-8, flow cytometry, enzyme-linked immunosorbent assay, reverse transcription-quantitative polymerase chain reaction, colorimetric detections, detection of the level of reactive oxygen species (ROS), mitochondrial ROS and mitochondrial membrane potential (MMP), immunofluorescence and western blotting. Our results showed that DHM increased Sev-induced cell viability of HT22 cells. Pretreatment with DHM attenuated apoptosis, inflammation, oxidative stress and mitochondrial dysfunction in Sev-elicited HT22 cells by remedying the abnormality of the indicators involved in these progresses, including apoptosis rate, the cleaved-caspase 3 expression, as well as the level of tumour necrosis factor α, interleukin (IL)-1β, IL-6, malondialdehyde, superoxide dismutase, catalase, ROS, mitochondrial ROS and MMP. Mechanically, pretreatment with DHM restored the Sev-induced the expression of SIRT1/FOXO3a pathway in HT22 cells. Blocking of SIRT1 counteracted the mitigatory effect of DHM on apoptosis, inflammation, oxidative stress and mitochondrial dysfunction in Sev-elicited HT22 cells. Collectively, pretreatment with DHM improved inflammation, oxidative stress and mitochondrial dysfunction via SIRT1/FOXO3a pathway in Sev-induced HT22 cells., (© 2024 John Wiley & Sons Australia, Ltd.)

Here we conducted wireless electrophysiological recording of hippocampal neurons from Egyptian fruit bats in the presence of human experimenters. In flying bats, many neurons modulated their activity depending on the identity of the human at the landing target. In stationary bats, many neurons carried significant spatial information about the position and identity of humans traversing the environment. Our results reveal that hippocampal activity is robustly modulated by the presence, movement and identity of human experimenters., (© 2024. The Author(s).)

Action potentials trigger neurotransmitter release at the presynaptic active zone with spatiotemporal precision. This is supported by protein machinery that mediates synaptic vesicle priming and clustering of Ca V 2 Ca 2+ channels nearby. One model posits that scaffolding proteins directly tether vesicles to Ca V 2s; however, here we find that at mouse hippocampal synapses, Ca V 2 clustering and vesicle priming are executed by separate machineries. Ca V 2 nanoclusters are positioned at variable distances from those of the priming protein Munc13. The active zone organizer RIM anchors both proteins but distinct interaction motifs independently execute these functions. In transfected cells, Liprin-α and RIM form co-assemblies that are separate from Ca V 2-organizing complexes. At synapses, Liprin-α1-Liprin-α4 knockout impairs vesicle priming but not Ca V 2 clustering. The cell adhesion protein PTPσ recruits Liprin-α, RIM and Munc13 into priming complexes without co-clustering Ca V 2s. We conclude that active zones consist of distinct machineries to organize Ca V 2s and prime vesicles, and Liprin-α and PTPσ specifically support priming site assembly., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)

While single-cell technologies have greatly advanced our comprehension of human brain cell types and functions, studies including large numbers of donors and multiple brain regions are needed to extend our understanding of brain cell heterogeneity. Integrating atlas-level single-cell data presents a chance to reveal rare cell types and cellular heterogeneity across brain regions. Here we present the Brain Cell Atlas, a comprehensive reference atlas of brain cells, by assembling single-cell data from 70 human and 103 mouse studies of the brain throughout major developmental stages across brain regions, covering over 26.3 million cells or nuclei from both healthy and diseased tissues. Using machine-learning based algorithms, the Brain Cell Atlas provides a consensus cell type annotation, and it showcases the identification of putative neural progenitor cells and a cell subpopulation of PCDH9 high microglia in the human brain. We demonstrate the gene regulatory difference of PCDH9 high microglia between hippocampus and prefrontal cortex and elucidate the cell-cell communication network. The Brain Cell Atlas presents an atlas-level integrative resource for comparing brain cells in different environments and conditions within the Human Cell Atlas., (© 2024. The Author(s).)

Intravascularly transplanted bone marrow cells, including bone marrow mononuclear cells (BM-MNC) and mesenchymal stem cells, transfer water-soluble molecules to cerebral endothelial cells via gap junctions. After transplantation of BM-MNC, this fosters hippocampal neurogenesis and enhancement of neuronal function. Herein, we report the impact of transplanted BM-MNC on neural stem cells (NSC) in the brain. Surprisingly, direct transfer of water-soluble molecules from transplanted BM-MNC and peripheral mononuclear cells to NSC in the hippocampus was observed already 10 min after cell transplantation, and transfer from BM-MNC to GFAP-positive cortical astrocytes was also observed. In vitro investigations revealed that BM-MNC abolish the expression of hypoxia-inducible factor-1α in astrocytes. We suggest that the transient and direct transfer of water-soluble molecules between cells in circulation and NSC in the brain may be one of the biological mechanisms underlying the repair of brain function.

The subiculum is a key region of the brain involved in the initiation of pathological activity in temporal lobe epilepsy, and local GABAergic inhibition is essential to prevent subicular-originated epileptiform discharges. Subicular pyramidal cells may be easily distinguished into two classes based on their different firing patterns. Here, we have compared the strength of the GABAa receptor-mediated inhibitory postsynaptic currents received by regular- vs. burst-firing subicular neurons and their dynamic modulation by the activation of μ opioid receptors. We have taken advantage of the sequential re-patching of the same cell to initially classify pyramidal neurons according to their firing patters, and then to measure GABAergic events triggered by the optogenetic stimulation of parvalbumin- and somatostatin-expressing interneurons. Activation of parvalbumin-expressing cells generated larger responses in postsynaptic burst-firing neurons whereas the opposite was observed for currents evoked by the stimulation of somatostatin-expressing interneurons. In all cases, events depended critically on ω-agatoxin IVA- but not on ω-conotoxin GVIA-sensitive calcium channels. Optogenetic GABAergic input originating from both parvalbumin- and somatostatin-expressing cells was reduced in amplitude following the exposure to a μ opioid receptor agonist. The kinetics of this pharmacological sensitivity was different in regular- vs. burst-firing neurons, but only when responses were evoked by the activation of parvalbumin-expressing neurons, whereas no differences were observed when somatostatin-expressing cells were stimulated. In conclusion, our results show that a high degree of complexity regulates the organizing principles of subicular GABAergic inhibition, with the interaction of pre- and postsynaptic diversity at multiple levels. KEY POINTS: Optogenetic stimulation of parvalbumin- and somatostatin-expressing interneurons (PVs and SOMs) triggers inhibitory postsynaptic currents (IPSCs) in both regular- and burst-firing (RFs and BFs) subicular pyramidal cells. The amplitude of optogenetically evoked IPSCs from PVs (PV-opto IPSCs) is larger in BFs whereas IPSCs generated by the light activation of SOMs (SOM-opto IPSCs) are larger in RFs. Both PV- and SOM-opto IPSCs critically depend on ω-agatoxin IVA-sensitive P/Q type voltage-gated calcium channels, whereas no major effects are observed following exposure to ω-conotoxin GVIA, suggesting no significant involvement of N-type channels. The amplitude of both PV- and SOM-opto IPSCs is reduced by the probable pharmacological activation of presynaptic μ opioid receptors, with a faster kinetics of the effect observed in PV-opto IPSCs from RFs vs. BFs, but not in SOM-opto IPSCs. These results help us understand the complex interactions between different layers of diversity regulating GABAergic input onto subicular microcircuits., (© 2024 The Author(s). The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

To support complex cognition, neuronal circuits must integrate information across multiple temporal scales, ranging from milliseconds to decades. Neuronal timescales describe the duration over which activity within a network persists, posing a putative explanatory mechanism for how information might be integrated over multiple temporal scales. Little is known about how timescales develop in human neural circuits or other model systems, limiting insight into how the functional dynamics necessary for cognition emerge. In our work, we show that neuronal timescales develop in a nonlinear fashion in human cortical organoids, which is partially replicated in dissociated rat hippocampus cultures. We use spectral parameterization of spiking activity to extract an estimate of neuronal timescale that is unbiased by coevolving oscillations. Cortical organoid timescales begin to increase around month 6 postdifferentiation. In rodent hippocampal dissociated cultures, we see that timescales decrease from in vitro days 13 - 23 before stabilizing. We speculate that cortical organoid development over the duration studied here reflects an earlier stage of a generalized developmental timeline in contrast to the rodent hippocampal cultures, potentially accounting for differences in timescale developmental trajectories. The fluctuation of timescales might be an important developmental feature that reflects the changing complexity and information capacity in developing neuronal circuits. NEW & NOTEWORTHY Neuronal timescales describe the persistence of activity within a network of neurons. Timescales were found to fluctuate with development in two model systems. In cortical organoids timescales increased, peaked, and then decreased throughout development; in rat hippocampal dissociated cultures timescales decreased over development. These distinct developmental models overlap to highlight a critical window in which timescales lengthen and contract, potentially indexing changes in the information capacity of neuronal systems.

Neurons receive thousands of inputs onto their dendritic arbour, where individual synapses undergo activity-dependent plasticity. Long-lasting changes in postsynaptic strengths correlate with changes in spine head volume. The magnitude and direction of such structural plasticity - potentiation (sLTP) and depression (sLTD) - depend upon the number and spatial distribution of stimulated synapses. However, how neurons allocate resources to implement synaptic strength changes across space and time amongst neighbouring synapses remains unclear. Here we combined experimental and modelling approaches to explore the elementary processes underlying multi-spine plasticity. We used glutamate uncaging to induce sLTP at varying number of synapses sharing the same dendritic branch, and we built a model incorporating a dual role Ca 2+ -dependent component that induces spine growth or shrinkage. Our results suggest that competition among spines for molecular resources is a key driver of multi-spine plasticity and that spatial distance between simultaneously stimulated spines impacts the resulting spine dynamics., (© 2024. The Author(s).)

Protein synthesis in response to neuronal activity, known as activity-dependent translation, is critical for synaptic plasticity and memory formation. However, the signaling cascades that couple neuronal activity to the translational events remain elusive. In this study, we identified the role of calmodulin (CaM), a conserved Ca 2+ -binding protein, in ribosomal RNA (rRNA) biogenesis in neurons. We found the CaM-regulated rRNA synthesis is Ca 2+ -dependent and necessary for nascent protein synthesis and axon growth in hippocampal neurons. Mechanistically, CaM interacts with nucleolar DEAD (Asp-Glu-Ala-Asp) box RNA helicase (DDX21) in a Ca 2+ -dependent manner to regulate nascent rRNA transcription within nucleoli. We further found CaM alters the conformation of DDX21 to liberate the DDX21-sequestered RPA194, the catalytic subunit of RNA polymerase I, to facilitate transcription of ribosomal DNA. Using high-throughput screening, we identified the small molecules batefenterol and indacaterol that attenuate the CaM-DDX21 interaction and suppress nascent rRNA synthesis and axon growth in hippocampal neurons. These results unveiled the previously unrecognized role of CaM as a messenger to link the activity-induced Ca 2+ influx to the nucleolar events essential for protein synthesis. We thus identified the ability of CaM to transmit information to the nucleoli of neurons in response to stimulation., Competing Interests: The authors declare no competing financial interests., (Copyright © 2024 the authors.)

The mammillary bodies (MBOs), a group of hypothalamic nuclei, play a pivotal role in memory formation and spatial navigation. They receive extensive inputs from the hippocampus through the fornix, but the physiological significance of these connections remains poorly understood. Damage to the MBOs is associated with various forms of anterograde amnesia. However, information about the physiological characteristics of the MBO is limited, primarily due to the limited number of studies that have directly monitored MBO activity along with population patterns of its upstream partners. Employing large-scale silicon probe recording in mice, we characterize MBO activity and its interaction with the subiculum across various brain states. We find that MBO cells are highly diverse in their relationship to theta, ripple, and slow oscillations. Several of the physiological features are inherited by the topographically organized inputs to MBO cells. Our study provides insights into the functional organization of the MBOs., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Imidacloprid (IMI) is a widely used neonicotinoid insecticide that poses risks for developmental neurotoxicity in mammals. The present study investigated the effects of maternal exposure to IMI on behaviors and adult neurogenesis in the hippocampal dentate gyrus (DG) of rat offspring. Dams were exposed to IMI via diet (83, 250, or 750 ppm in diet) from gestational day 6 until day 21 post-delivery on weaning, and offspring were maintained until adulthood on postnatal day 77. In the neurogenic niche, 750-ppm IMI decreased numbers of late-stage neural progenitor cells (NPCs) and post-mitotic immature granule cells by suppressing NPC proliferation and ERK1/2-FOS-mediated synaptic plasticity of granule cells on weaning. Suppressed reelin signaling might be responsible for the observed reductions of neurogenesis and synaptic plasticity. In adulthood, IMI at ≥ 250 ppm decreased neural stem cells by suppressing their proliferation and increasing apoptosis, and mature granule cells were reduced due to suppressed NPC differentiation. Behavioral tests revealed increased spontaneous activity in adulthood at 750 ppm. IMI decreased hippocampal acetylcholinesterase activity and Chrnb2 transcript levels in the DG on weaning and in adulthood. IMI increased numbers of astrocytes and M1-type microglia in the DG hilus, and upregulated neuroinflammation and oxidative stress-related genes on weaning. In adulthood, IMI increased malondialdehyde level and number of M1-type microglia, and downregulated neuroinflammation and oxidative stress-related genes. These results suggest that IMI persistently affected cholinergic signaling, induced neuroinflammation and oxidative stress during exposure, and increased sensitivity to oxidative stress after exposure in the hippocampus, causing hyperactivity and progressive suppression of neurogenesis in adulthood. The no-observed-adverse-effect level of IMI for offspring behaviors and hippocampal neurogenesis was determined to be 83 ppm (5.5-14.1 mg/kg body weight/day)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

The astrocyte-to-neuron lactate shuttle model entails that, upon glutamatergic neurotransmission, glycolytically derived pyruvate in astrocytes is mainly converted to lactate instead of being entirely catabolized in mitochondria. The mechanism of this metabolic rewiring and its occurrence in human brain are unclear. Here by using immunohistochemistry (4 brains) and imaging mass cytometry (8 brains) we show that astrocytes of the adult human neocortex and hippocampal formation express barely detectable amounts of mitochondrial proteins critical for performing oxidative phosphorylation (OXPHOS). These data are corroborated by queries of transcriptomes (107 brains) of neuronal versus non-neuronal cells fetched from the Allen Institute for Brain Science for genes coding for a much larger repertoire of entities contributing to OXPHOS, showing that human non-neuronal elements barely expressed mRNAs coding for such proteins. With less OXPHOS, human brain astrocytes are thus bound to produce more lactate to avoid interruption of glycolysis., (© 2024. The Author(s).)

Glutamate (Glu) is a major excitatory neurotransmitter in the brain, essential for synaptic plasticity, neuronal activity, and memory formation. However, its dysregulation leads to excitotoxicity, implicated in neurodegenerative diseases and brain ischemia. Vesicular glutamate transporters (VGLUTs) regulate Glu loading into synaptic vesicles, crucial for maintaining optimal extracellular Glu levels. This study investigates the neuroprotective effects of VGLUT1 inhibition in HT22 cells overexpressing VGLUT1 under oxygen glucose deprivation (OGD) conditions. HT22 cells, a hippocampal neuron model, were transduced with lentiviral vectors to overexpress VGLUT1. Cells were subjected to OGD, with pre-incubation of Chicago Sky Blue 6B (CSB6B), an unspecific VGLUT inhibitor. Cell viability, lactate dehydrogenase (LDH) release, mitochondrial membrane potential, and hypoxia-related protein markers (PARP1, AIF, NLRP3) were assessed. Results indicated that VGLUT1 overexpression increased vulnerability to OGD, evidenced by higher LDH release and reduced cell viability. CSB6B treatment improved cell viability and reduced LDH release in OGD conditions, particularly at 0.1 μM and 1.0 μM concentrations. Moreover, CSB6B preserved mitochondrial membrane potential and decreased levels of PARP1, AIF, and NLRP3 proteins, suggesting neuroprotective effects through mitigating excitotoxicity. This study demonstrates that VGLUT1 inhibition could be a promising therapeutic strategy for ischemic brain injury, warranting further investigation into selective VGLUT1 inhibitors., (© 2024. The Author(s).)

Mature neurons have stable dendritic architecture, which is essential for the nervous system to operate correctly. The ability to undergo structural plasticity, required to support adaptive processes like memory formation, is still present in mature neurons. It is unclear what molecular and cellular processes control this delicate balance between dendritic structural plasticity and stabilization. Failures in the preservation of optimal dendrite structure due to atrophy or maladaptive plasticity result in abnormal connectivity and are associated with various neurological diseases. Vascular endothelial growth factor D (VEGFD) is critical for the maintenance of mature dendritic trees. Here, we describe how VEGFD affects the neuronal cytoskeleton and demonstrate that VEGFD exerts its effects on dendrite stabilization by influencing the actin cortex and reducing microtubule dynamics. Further, we found that during synaptic activity-induced structural plasticity VEGFD is downregulated. Our findings revealed that VEGFD, acting on its cognate receptor VEGFR3, opposes structural changes by negatively regulating dendrite growth in cultured hippocampal neurons and in vivo in the adult mouse hippocampus with consequences on memory formation. A phosphoproteomic screening identified several regulatory proteins of the cytoskeleton modulated by VEGFD. Among the actin cortex-associated proteins, we found that VEGFD induces dephosphorylation of ezrin at tyrosine 478 via activation of the striatal-enriched protein tyrosine phosphatase (STEP). Activity-triggered structural plasticity of dendrites was impaired by expression of a phospho-deficient mutant ezrin in vitro and in vivo. Thus, VEGFD governs the equilibrium between stabilization and plasticity of dendrites by acting as a molecular brake of structural remodeling., (© 2024. The Author(s).)

Long-term synaptic plasticity is typically associated with morphological changes in synaptic connections. However, the molecular mechanisms coupling functional and structural aspects of synaptic plasticity are still poorly defined. The catalytic activity of type I phosphoinositide-3-kinase (PI3K) is required for specific forms of synaptic plasticity, such as NMDA receptor-dependent long-term potentiation (LTP) and mGluR-dependent long-term depression (LTD). On the other hand, PI3K signaling has been linked to neuronal growth and synapse formation. Consequently, PI3Ks are promising candidates to coordinate changes in synaptic strength with structural remodeling of synapses. To investigate this issue, we targeted individual regulatory subunits of type I PI3Ks in hippocampal neurons and employed a combination of electrophysiological, biochemical and imaging techniques to assess their role in synaptic plasticity. We found that a particular regulatory isoform, p85α, is selectively required for LTP. This specificity is based on its BH domain, which engages the small GTPases Rac1 and Cdc42, critical regulators of the actin cytoskeleton. Moreover, cofilin, a key regulator of actin dynamics that accumulates in dendritic spines after LTP induction, failed to do so in the absence of p85α or when its BH domain was overexpressed as a dominant negative construct. Finally, in agreement with this convergence on actin regulatory mechanisms, the presence of p85α in the PI3K complex determined the extent of actin polymerization in dendritic spines during LTP. Therefore, this study reveals a molecular mechanism linking structural and functional synaptic plasticity through the coordinate action of PI3K catalytic activity and a specific isoform of the regulatory subunits., (© 2024. The Author(s).)

Neuronal activity is an energy-intensive process that is largely sustained by instantaneous fuel utilization and ATP synthesis. However, how neurons couple ATP synthesis rate to fuel availability is largely unknown. Here, we demonstrate that the metabolic sensor enzyme O-linked N-acetyl glucosamine (O-GlcNAc) transferase regulates neuronal activity-driven mitochondrial bioenergetics in hippocampal and cortical neurons. We show that neuronal activity upregulates O-GlcNAcylation in mitochondria. Mitochondrial O-GlcNAcylation is promoted by activity-driven glucose consumption, which allows neurons to compensate for high energy expenditure based on fuel availability. To determine the proteins that are responsible for these adjustments, we mapped the mitochondrial O-GlcNAcome of neurons. Finally, we determine that neurons fail to meet activity-driven metabolic demand when O-GlcNAcylation dynamics are prevented. Our findings suggest that O-GlcNAcylation provides a fuel-dependent feedforward control mechanism in neurons to optimize mitochondrial performance based on neuronal activity. This mechanism thereby couples neuronal metabolism to mitochondrial bioenergetics and plays a key role in sustaining energy homeostasis., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The morphology of dendritic spines, the postsynaptic compartment of most excitatory synapses, decisively modulates the function of neuronal circuits as also evident from human brain disorders associated with altered spine density or morphology. Actin filaments (F-actin) form the backbone of spines, and a number of actin-binding proteins (ABP) have been implicated in shaping the cytoskeleton in mature spines. Instead, only little is known about the mechanisms that control the reorganization from unbranched F-actin of immature spines to the complex, highly branched cytoskeleton of mature spines. Here, we demonstrate impaired spine maturation in hippocampal neurons upon genetic inactivation of cyclase-associated protein 1 (CAP1) and CAP2, but not of CAP1 or CAP2 alone. We found a similar spine maturation defect upon overactivation of inverted formin 2 (INF2), a nucleator of unbranched F-actin with hitherto unknown synaptic function. While INF2 overactivation failed in altering spine density or morphology in CAP-deficient neurons, INF2 inactivation largely rescued their spine defects. From our data we conclude that CAPs inhibit INF2 to induce spine maturation. Since we previously showed that CAPs promote cofilin1-mediated cytoskeletal remodeling in mature spines, we identified them as a molecular switch that control transition from filopodia-like to mature spines., (© 2024. The Author(s).)

Memories are dynamic constructs whose properties change with time and experience. The biological mechanisms underpinning these dynamics remain elusive, particularly concerning how shifts in the composition of memory-encoding neuronal ensembles influence the evolution of a memory over time. By targeting developmentally distinct subpopulations of principal neurons, we discovered that memory encoding resulted in the concurrent establishment of multiple memory traces in the mouse hippocampus. Two of these traces were instantiated in subpopulations of early- and late-born neurons and followed distinct reactivation trajectories after encoding. The divergent recruitment of these subpopulations underpinned gradual reorganization of memory ensembles and modulated memory persistence and plasticity across multiple learning episodes. Thus, our findings reveal profound and intricate relationships between ensemble dynamics and the progression of memories over time.

AMPA-type receptors (AMPARs) are rapidly inserted into synapses undergoing plasticity to increase synaptic transmission, but it is not fully understood if and how AMPAR-containing vesicles are selectively trafficked to these synapses. Here, we developed a strategy to label AMPAR GluA1 subunits expressed from their endogenous loci in cultured rat hippocampal neurons and characterized the motion of GluA1-containing vesicles using single-particle tracking and mathematical modeling. We find that GluA1-containing vesicles are confined and concentrated near sites of stimulation-induced structural plasticity. We show that confinement is mediated by actin polymerization, which hinders the active transport of GluA1-containing vesicles along the length of the dendritic shaft by modulating the rheological properties of the cytoplasm. Actin polymerization also facilitates myosin-mediated transport of GluA1-containing vesicles to exocytic sites. We conclude that neurons utilize F-actin to increase vesicular GluA1 reservoirs and promote exocytosis proximal to the sites of synaptic activity., Competing Interests: VW, PH, HL, DW, MD, ZL No competing interests declared, EO Erin K O'Shea is President of the Howard Hughes Medical Institute, one of the three founding funders of eLife, and a member of eLife's Board of Directors, (© 2024, Wong et al.)

It has long been assumed that activity patterns persist in neuronal circuits after they are first experienced, as part of the process of information processing and storage by the brain. However, these "reverberations" of current activity have not been directly observed on a single-neuron level in a mammalian system. Here we demonstrate that specific induced activity patterns are retained in mature cultured hippocampal neuronal networks. Neurons within the network are induced to fire at a single frequency or in a more complex pattern containing two distinct frequencies. After the stimulation was stopped, the subsequent neuronal activity of hundreds of neurons in the network was monitored. In the case of single-frequency stimulation, it was observed that many of the neurons continue to fire at the same frequency that they were stimulated to fire at. Using a recurrent neural network trained to detect specific, more complex patterns, we found that the multiple-frequency stimulation patterns were also retained within the neuronal network. Moreover, it appears that the component frequencies of the more complex patterns are stored in different populations of neurons and neuron subtypes., Competing Interests: The authors declare no competing financial interests., (Copyright © 2024 Niewinski et al.)

The hippocampus receives sequences of sensory inputs from the cortex during exploration and encodes the sequences with millisecond precision. We developed a predictive autoencoder model of the hippocampus including the trisynaptic and monosynaptic circuits from the entorhinal cortex (EC). CA3 was trained as a self-supervised recurrent neural network to predict its next input. We confirmed that CA3 is predicting ahead by analyzing the spike coupling between simultaneously recorded neurons in the dentate gyrus, CA3, and CA1 of the mouse hippocampus. In the model, CA1 neurons signal prediction errors by comparing CA3 predictions to the next direct EC input. The model exhibits the rapid appearance and slow fading of CA1 place cells and displays replay and phase precession from CA3. The model could be learned in a biologically plausible way with error-encoding neurons. Similarities between the hippocampal and thalamocortical circuits suggest that such computation motif could also underlie self-supervised sequence learning in the cortex., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Brain oscillations are crucial for perception, memory, and behavior. Parvalbumin-expressing (PV) interneurons are critical for these oscillations, but their population dynamics remain unclear. Using voltage imaging, we simultaneously recorded membrane potentials in up to 26 PV interneurons in vivo during hippocampal ripple oscillations in mice. We found that PV cells generate ripple-frequency rhythms by forming highly dynamic cell assemblies. These assemblies exhibit rapid and significant changes from cycle to cycle, varying greatly in both size and membership. Importantly, this variability is not just random spiking failures of individual neurons. Rather, the activities of other PV cells contain significant information about whether a PV cell spikes or not in a given cycle. This coordination persists without network oscillations, and it exists in subthreshold potentials even when the cells are not spiking. Dynamic assemblies of interneurons may provide a new mechanism to modulate postsynaptic dynamics and impact cognitive functions flexibly and rapidly., Competing Interests: Declaration of interests US patents 9,933,417 and 11,091,643 and US patent application US 2021/0085805, describing azetidine-containing fluorophores and variant compositions (with inventors L.D.L. and Q.Z.), are assigned to the Howard Hughes Medical Institute (HHMI). US patent 11,385,236, describing chemigenetic voltage indicators (with inventors E.R.S., L.D.L., and A.S.A.), is assigned to HHMI. L.D.L. serves on the Cell Chemical Biology advisory board. L.D.L. is a founder and shareholder of Eikon Therapeutics., (Copyright © 2024 Elsevier Inc. All rights reserved.)

This study investigated the role and mechanism of ligustilide(LIG) in attenuating oxygen-glucose deprivation/reoxyge-nation(OGD/R)-induced damage to mouse hippocampal neuron cells(HT22) by inhibiting ferroptosis through mitochondrial ferritin(FtMt). An in vitro model of OGD/R-induced HT22 cell damage was established. HT22 cells were randomly divided into normal group, model group, LIG groups(5, 10, and 20 μmol·L~(-1)), and ferrostatin-1(Fer-1, 2 μmol·L~(-1)) group. Cell viability was mea-sured using the CCK-8 method, and lactate dehydrogenase(LDH) release was measured using an LDH assay kit. Cell morphology was observed under an inverted microscope, and mitochondrial ultrastructure was observed using transmission electron microscopy. Intracellular Fe~(2+) content was detected using a chemiluminescence method. To further investigate the mechanism of FtMt inhibition of ferroptosis, FtMt in HT22 cells was silenced and divided into normal group, model group, LIG group(20 μmol·L~(-1)), si-NC group, si-FtMt group, and si-FtMt+20 μmol·L~(-1) LIG group. Immunofluorescence and Western blot were used to detect FtMt expression. Chemiluminescence was used to measure the content of NADPH/NADP~+, GSH, MDA, and ATP in HT22 cells. The mtROS fluorescence intensity was observed by laser confocal microscopy, and intracellular Fe~(2+) content was measured by flow cytometry. The expression of ferroptosis-related proteins Ferrtin, GPX4, and ACSL4 was detected by Western blot. The results showed that compared with the model group, LIG significantly increased the survival rate of HT22 cells, improved the morphology of damaged HT22 cells and mitochondrial ultrastructure, decreased intracellular Fe~(2+) content, and reduced the expression of the pro-ferroptosis protein ACSL4 while increasing the expression of anti-ferroptosis proteins Ferrtin and GPX4. After silencing FtMt, LIG promoted FtMt expression. Compared with the si-FtMt group, LIG significantly increased the content of NADPH/NADP~+ and GSH, reduced mtROS fluorescence intensity and MDA content, increased ATP activity, decreased intracellular Fe~(2+) content, inhibited the expression of pro-ferroptosis protein ACSL4, and increased the expression of anti-ferroptosis proteins Ferrtin and GPX4. In summary, LIG improved mitochondrial function by upregula-ting FtMt expression to inhibit ferroptosis, thereby alleviating OGD/R-induced damage to HT22 cells.

We have investigated the hippocampal connectivity of the marmoset presubiculum (PreS) and reported that major connections of PreS in the rat were conserved in the marmoset. Moreover, our results indicated the presence of several additional projections that were almost absent in the rat brain, but abundant in the marmoset, such as direct projections from CA1 to PreS. However, little is known about the connectivity between the frontal brain regions and PreS or hippocampal formation. Therefore, we investigated the distribution of cells of the origins and terminals of the presubicular and hippocampal projections in the marmoset frontal brain regions using the retrograde and anterograde tracer cholera toxin B subunit. In cases of tracer injections into all layers of PreS, many neurons and terminals were labeled in the claustrum-endopiriform (Cl-En) complex almost entirely along the rostrocaudal axis. Even in cases where the injection site involved the superficial (not deep) layers of PreS, labeled neurons and terminals were distributed over a wide rostrocaudal range of the Cl-En complex, but their number and density were significantly lower than the whole-layer injection cases. In cases where the injection site was confined to the hippocampal formation, labeled cells and terminals were localized at a restricted portion of the Cl-En complex. Here, we demonstrate for what we believe to be the first time the strong, reciprocal connections of the Cl-En complex with PreS and projections from the Cl-En complex to the hippocampal regions (CA1 and the subiculum) in the marmoset. Our findings indicate that the Cl-En complex may exert a strong influence on the cortical and subcortical outputs from PreS and, in turn, the entire memory circuitry in the marmoset brain., (© 2024 The Author(s). The Journal of Comparative Neurology published by Wiley Periodicals LLC.)

Hippocampal place cells are influenced by both self-motion (idiothetic) signals and external sensory landmarks as an animal navigates its environment. To continuously update a position signal on an internal 'cognitive map', the hippocampal system integrates self-motion signals over time, a process that relies on a finely calibrated path integration gain that relates movement in physical space to movement on the cognitive map. It is unclear whether idiothetic cues alone, such as optic flow, exert sufficient influence on the cognitive map to enable recalibration of path integration, or if polarizing position information provided by landmarks is essential for this recalibration. Here, we demonstrate both recalibration of path integration gain and systematic control of place fields by pure optic flow information in freely moving rats. These findings demonstrate that the brain continuously rebalances the influence of conflicting idiothetic cues to fine-tune the neural dynamics of path integration, and that this recalibration process does not require a top-down, unambiguous position signal from landmarks., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Mass spectrometry has revolutionized cell signaling research by vastly simplifying the analysis of many thousands of phosphorylation sites in the human proteome. Defining the cellular response to perturbations is crucial for further illuminating the functionality of the phosphoproteome. Here we describe µPhos ('microPhos'), an accessible phosphoproteomics platform that permits phosphopeptide enrichment from 96-well cell culture and small tissue amounts in <8 h total processing time. By greatly minimizing transfer steps and liquid volumes, we demonstrate increased sensitivity, >90% selectivity, and excellent quantitative reproducibility. Employing highly sensitive trapped ion mobility mass spectrometry, we quantify ~17,000 Class I phosphosites in a human cancer cell line using 20 µg starting material, and confidently localize ~6200 phosphosites from 1 µg. This depth covers key signaling pathways, rendering sample-limited applications and perturbation experiments with hundreds of samples viable. We employ µPhos to study drug- and time-dependent response signatures in a leukemia cell line, and by quantifying 30,000 Class I phosphosites in the mouse brain we reveal distinct spatial kinase activities in subregions of the hippocampal formation., (© 2024. The Author(s).)

Aim: Understanding the physiological role of ATP6V1A, a component of the cytosolic V 1 domain of the proton pump vacuolar ATPase, in regulating neuronal development and function., Methods: Modeling loss of function of Atp6v1a in primary murine hippocampal neurons and studying neuronal morphology and function by immunoimaging, electrophysiological recordings and electron microscopy., Results: Atp6v1a depletion affects neurite elongation, stabilization, and function of excitatory synapses and prevents synaptic rearrangement upon induction of plasticity. These phenotypes are due to an overall decreased expression of the V 1 subunits, that leads to impairment of lysosomal pH-regulation and autophagy progression with accumulation of aberrant lysosomes at neuronal soma and of enlarged vacuoles at synaptic boutons., Conclusions: These data suggest a physiological role of ATP6V1A in the surveillance of synaptic integrity and plasticity and highlight the pathophysiological significance of ATP6V1A loss in the alteration of synaptic function that is associated with neurodevelopmental and neurodegenerative diseases. The data further support the pivotal involvement of lysosomal function and autophagy flux in maintaining proper synaptic connectivity and adaptive neuronal properties., (© 2024 The Author(s). Acta Physiologica published by John Wiley & Sons Ltd on behalf of Scandinavian Physiological Society.)

Adult neural stem cells (NSCs) in the hippocampal dentate gyrus continuously proliferate and generate new neurons throughout life. Although various functions of organelles are closely related to the regulation of adult neurogenesis, the role of endoplasmic reticulum (ER)-related molecules in this process remains largely unexplored. Here we show that Derlin-1, an ER-associated degradation component, spatiotemporally maintains adult hippocampal neurogenesis through a mechanism distinct from its established role as an ER quality controller. Derlin-1 deficiency in the mouse central nervous system leads to the ectopic localization of newborn neurons and impairs NSC transition from active to quiescent states, resulting in early depletion of hippocampal NSCs. As a result, Derlin-1-deficient mice exhibit phenotypes of increased seizure susceptibility and cognitive dysfunction. Reduced Stat5b expression is responsible for adult neurogenesis defects in Derlin-1-deficient NSCs. Inhibition of histone deacetylase activity effectively induces Stat5b expression and restores abnormal adult neurogenesis, resulting in improved seizure susceptibility and cognitive dysfunction in Derlin-1-deficient mice. Our findings indicate that the Derlin-1-Stat5b axis is indispensable for the homeostasis of adult hippocampal neurogenesis., (© 2024. The Author(s).)