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Active dendritic integrative mechanisms such as regenerative dendritic spikes enrich the information processing abilities of neurons and fundamentally contribute to behaviorally relevant computations. Dendritic Ca 2+ spikes are generally thought to produce plateau-like dendritic depolarization and somatic complex spike burst (CSB) firing, which can initiate rapid changes in spatial coding properties of hippocampal pyramidal cells (PCs). However, here we reveal that a morpho-topographically distinguishable subpopulation of rat and mouse hippocampal CA3PCs exhibits compound apical dendritic Ca 2+ spikes with unusually short duration that do not support the firing of sustained CSBs. These Ca 2+ spikes are mediated by L-type Ca 2+ channels and their time course is restricted by A- and M-type K + channels. Cholinergic activation powerfully converts short Ca 2+ spikes to long-duration forms, and facilitates and prolongs CSB firing. We propose that cholinergic neuromodulation controls the ability of a CA3PC subtype to generate sustained plateau potentials, providing a state-dependent dendritic mechanism for memory encoding and retrieval., Competing Interests: Competing interests statement:The authors declare no competing interest.

Neurons often grow highly branched and cell-type specific dendrite morphologies to receive and integrate information, which is the basis of precise neural circuit formation. Previous studies have identified numerous mechanisms that promote dendrite branching. In contrast, it is much less understood how this process is negatively regulated. Here we show that EAT-17/EVI5 acts together with the dynein adaptor protein BICD-1 and the motor protein dynein in C. elegans epidermal cells to restrict branching of PVD sensory dendrites. Loss-of-function mutants of these genes cause both ectopic branching and accumulation of the dendrite branching ligand SAX-7/L1CAM on epidermal plasma membranes. Mutants of genes regulating endo-lysosomal trafficking, including rab-5/RAB5 and dyn-1/DNM1, show similar defects. Biochemical characterization, genetic analysis, and imaging results support that EAT-17 and BICD-1 directly interact with each other and function in the endocytic degradation pathway to remove ectopically localized dendrite branching ligands to restrict abnormal branching., (© 2024. The Author(s).)

Background: In mucopolysaccharidosis type III (MPS III, also known as Sanfilippo syndrome), a pediatric neurodegenerative disorder, accumulation of abnormal glycosaminoglycans (GAGs) induces severe neuroinflammation by triggering the microglial pro-inflammatory cytokines production via a TLR4-dependent pathway. But the extent of the microglia contribution to the MPS III neuropathology remains unclear. Extracellular vesicles (EVs) mediate intercellular communication and are known to participate in the pathogenesis of adult neurodegenerative diseases. However, characterization of the molecular profiles of EVs released by MPS III microglia and their effects on neuronal functions have not been described., Methods: Here, we isolated EVs secreted by the microglial cells after treatment with GAGs purified from urines of Sanfilippo patients (sfGAGs-EVs) or from age-matched healthy subjects (nGAGs-EVs) to explore the EVs' proteins and small RNA profiles using LC-MS/MS and RNA sequencing. We next performed a functional assay by immunofluorescence following nGAGs- or sfGAGs-EVs uptake by WT primary cortical neurons and analyzed their extensions metrics after staining of βIII-tubulin and MAP2 by confocal microscopy., Results: Functional enrichment analysis for both proteomics and RNA sequencing data from sfGAGs-EVs revealed a specific content involved in neuroinflammation and neurodevelopment pathways. Treatment of cortical neurons with sfGAGs-EVs induced a disease-associated phenotype demonstrated by a lower total neurite surface area, an impaired somatodendritic compartment, and a higher number of immature dendritic spines., Conclusions: This study shows, for the first time, that GAGs from patients with Sanfilippo syndrome can induce microglial secretion of EVs that deliver a specific molecular message to recipient naive neurons, while promoting the neuroinflammation, and depriving neurons of neurodevelopmental factors. This work provides a framework for further studies of biomarkers to evaluate efficiency of emerging therapies., (© 2024. The Author(s).)

Dendritic morphology is typically highly branched, and the branching and synaptic abundance of dendrites can enhance the receptive range of neurons and the diversity of information received, thus providing the basis for information processing in the nervous system. Once dendritic development is aberrantly compromised or damaged, it may lead to abnormal connectivity of the neural network, affecting the function and stability of the nervous system and ultimately triggering a series of neurological disorders. Research on the regulation of dendritic developmental processes has flourished, and much progress is now being made in its regulatory mechanisms. Noteworthily, dendrites are characterized by an extremely complex dendritic arborization that cannot be attributed to individual protein functions alone, requiring a systematic analysis of the intrinsic and extrinsic signals and the coordinated roles among them. Actin cytoskeleton organization and membrane vesicle trafficking are required during dendrite development, with actin providing tracks for vesicles and vesicle trafficking in turn providing material for actin assembly. In this review, we focus on these two basic biological processes and discuss the molecular mechanisms and their synergistic effects underlying the morphogenesis of neuronal dendrites. We also offer insights and discuss strategies for the potential preventive and therapeutic treatment of neuropsychiatric disorders., Competing Interests: Conflict of interest The authors declare no competing interests., (Copyright © 2024 Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Ltd. All rights reserved.)

α-Klotho (α-Kl) is a modulator of aging, neuroprotection, and cognition. Transcription of the Klotho gene produces two splice variants-a membrane protein (mKl), which can be cleaved and released into the extracellular milieu, and a truncated secreted form (sKl). Despite mounting evidence supporting a role for α-Kl in brain function, the specific roles of α-Kl isoforms in neuronal development remain elusive. Here, we examined α-Kl protein levels in rat brain and observed region-specific expression in the adult that differs between isoforms. In the developing hippocampus, levels of isoforms decrease after the third postnatal week, marking the end of the critical period for development. We overexpressed α-Kl isoforms in primary cultures of rat cortical neurons and evaluated effects on brain-derived neurotrophic factor (BDNF) signaling. Overexpression of either isoform attenuated BDNF-mediated signaling and reduced intracellular Ca 2+ levels, with mKl promoting a greater effect. mKl or sKl overexpression in hippocampal neurons resulted in a partially overlapping reduction in secondary dendrite branching. Moreover, mKl overexpression increased primary dendrite number. BDNF treatment of neurons overexpressing sKl resulted in a dendrite branching phenotype similar to control neurons. In neurons overexpressing mKl, BDNF treatment restored branching of secondary and higher order dendrites close, but not distal, to the soma. Taken together, the data presented support the idea that sKl and mKl play distinct roles in neuronal development, and specifically, in dendrite morphogenesis., (© 2024. The Author(s).)

The intestinal lumen is rich in gut microbial metabolites that serve as signaling molecules for gut immune cells. G-protein-coupled receptors (GPCRs) sense metabolites and can act as key mediators that translate gut luminal signals into host immune responses. However, the impacts of gut microbe-GPCR interactions on human physiology have not been fully elucidated. Here, we show that GPR31, which is activated by the gut bacterial metabolite pyruvate, is specifically expressed on type 1 conventional dendritic cells (cDC1s) in the lamina propria of the human intestine. Using human induced pluripotent stem cell-derived cDC1s and a monolayer human gut organoid coculture system, we show that cDC1s extend their dendrites toward pyruvate on the luminal side, forming transepithelial dendrites (TED). Accordingly, GPR31 activation via pyruvate enhances the fundamental function of cDC1 by allowing efficient uptake of gut luminal antigens, such as dietary compounds and bacterial particles through TED formation. Our results highlight the role of GPCRs in tuning the human gut immune system according to local metabolic cues., Competing Interests: Competing interests statement:The authors declare no competing interest.

The formation and precise positioning of axons and dendrites are crucial for the development of neural circuits. Although juxtacrine signaling via cell-cell contact is known to influence these processes, the specific structures and mechanisms regulating neuronal process positioning within the central nervous system (CNS) remain to be fully identified. Our study investigates motoneuron 24 (MN24) in the Drosophila embryonic CNS, which is characterized by a complex yet stereotyped axon projection pattern, known as "axonal routing." In this motoneuron, the primary dendritic branches project laterally toward the midline, specifically emerging at the sites where axons turn. We observed that Scp2-positive neurons contribute to the lateral fascicle structure in the ventral nerve cord (VNC) near MN24 dendrites. Notably, the knockout of the Down syndrome cell adhesion molecule ( Dscam1 ) results in the loss of dendrites and disruption of proper axonal routing in MN24, while not affecting the formation of the fascicle structure. Through cell-type specific knockdown and rescue experiments of Dscam1, we have determined that the interaction between MN24 and Scp2-positive fascicle, mediated by Dscam1, promotes the development of both dendrites and axonal routing. Our findings demonstrate that the holistic configuration of neuronal structures, such as axons and dendrites, within single motoneurons can be governed by local contact with the adjacent neuron fascicle, a novel reference structure for neural circuitry wiring., Competing Interests: The authors declare no competing financial interests., (Copyright © 2024 Bui and Kamiyama.)

Dendrite defects and loss are early cellular alterations observed across neurodegenerative diseases that play a role in early disease pathogenesis. Dendrite degeneration can be modeled by expressing pathogenic polyglutamine disease transgenes in Drosophila neurons in vivo. Here, we show that we can protect against dendrite loss in neurons modeling neurodegenerative polyglutamine diseases through injury to a single primary dendrite branch. We find that this neuroprotection is specific to injury-induced activation of dendrite regeneration: neither injury to the axon nor injury just to surrounding tissues induces this response. We show that the mechanism of this regenerative response is stabilization of the actin (but not microtubule) cytoskeleton. We also demonstrate that this regenerative response may extend to other neurodegenerative diseases. Together, we provide evidence that activating dendrite regeneration pathways has the potential to slow-or even reverse-dendrite loss in neurodegenerative disease., (© 2024. The Author(s).)

Reelin, a secreted glycoprotein, plays a crucial role in guiding neocortical neuronal migration, dendritic outgrowth and arborization, and synaptic plasticity in the adult brain. Reelin primarily operates through the canonical lipoprotein receptors apolipoprotein E receptor 2 (Apoer2) and very low-density lipoprotein receptor (Vldlr). Reelin also engages with noncanonical receptors and unidentified coreceptors; however, the effects of which are less understood. Using high-throughput tandem mass tag (TMT) liquid chromatography tandem mass spectrometry (LC-MS/MS)-based proteomics and gene set enrichment analysis (GSEA), we identified both shared and unique intracellular pathways activated by Reelin through its canonical and noncanonical signaling in primary murine neurons of either sex during dendritic growth and arborization. We observed pathway cross talk related to regulation of cytoskeleton, neuron projection development, protein transport, and actin filament-based process. We also found enriched gene sets exclusively by the noncanonical Reelin pathway including protein translation, mRNA metabolic process, and ribonucleoprotein complex biogenesis suggesting Reelin fine-tunes neuronal structure through distinct signaling pathways. A key discovery is the identification of aldolase A, a glycolytic enzyme and actin-binding protein, as a novel effector of Reelin signaling. Reelin induced de novo translation and mobilization of aldolase A from the actin cytoskeleton. We demonstrated that aldolase A is necessary for Reelin-mediated dendrite growth and arborization in primary murine neurons and mouse brain cortical neurons. Interestingly, the function of aldolase A in dendrite development is independent of its known role in glycolysis. Altogether, our findings provide new insights into the Reelin-dependent signaling pathways and effector proteins that are crucial for dendritic development., Competing Interests: The authors declare no competing financial interests., (Copyright © 2024 the authors.)

Mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE) is an important cause of drug-resistant epilepsy. A significant subset of individuals diagnosed with MOGHE display somatic mosaicism for loss-of-function variants in SLC35A2, which encodes the UDP-galactose transporter. We developed a mouse model to investigate how disruption of this transporter leads to a malformation of cortical development. We used in utero electroporation and CRISPR/Cas9 to knockout Slc35a2 in a subset of layer 2/3 cortical neuronal progenitors in the developing brains of male and female fetal mice to model mosaic expression. Mosaic Slc35a2 knockout was verified through next-generation sequencing and immunohistochemistry of GFP-labelled transfected cells. Histology of brain tissue in mosaic Slc35a2 knockout mice revealed the presence of upper layer-derived cortical neurons in the white matter. Reconstruction of single filled neurons identified altered dendritic arborisation with Slc35a2 knockout neurons having increased complexity. Whole-cell electrophysiological recordings revealed that Slc35a2 knockout neurons display reduced action potential firing, increased afterhyperpolarisation duration and reduced burst-firing when compared with control neurons. Mosaic Slc35a2 knockout mice also exhibited significantly increased epileptiform spiking and increased locomotor activity. We successfully generated a mouse model of mosaic Slc35a2 deficiency, which recapitulates features of the human phenotype, including impaired neuronal migration. We show that knockout in layer 2/3 cortical neuron progenitors is sufficient to disrupt neuronal excitability, increase epileptiform activity and cause hyperactivity in mosaic mice. Our mouse model provides an opportunity to further investigate the disease mechanisms that contribute to MOGHE and facilitate the development of precision therapies., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:, (Copyright © 2024. Published by Elsevier Inc.)

Neurons are highly polarized cells with dendrites and axons. Dendrites, which receive sensory information or input from other neurons, often display elaborately branched morphologies. While mechanisms that promote dendrite branching have been widely studied, less is known about the mechanisms that restrict branching. Using the nematode Caenorhabditis elegans, we identify rabr-1 (for Rab-related gene 1) as a factor that restricts branching of the elaborately branched dendritic trees of PVD and FLP somatosensory neurons. Animals mutant for rabr-1 show excessively branched dendrites throughout development and into adulthood in areas where the dendrites overlay epidermal tissues. Phylogenetic analyses show that RABR-1 displays similarity to small GTPases of the Rab-type, although based on sequence alone, no clear vertebrate ortholog of RABR-1 can be identified. We find that rabr-1 is expressed and can function in epidermal tissues, suggesting that rabr-1 restricts dendritic branching cell-nonautonomously. Genetic experiments further indicate that for the formation of ectopic branches rabr-1 mutants require the genes of the Menorin pathway, which have been previously shown to mediate dendrite morphogenesis of somatosensory neurons. A translational reporter for RABR-1 reveals a subcellular localization to punctate, perinuclear structures, which correlates with endosomal and autophagosomal markers, but anticorrelates with lysosomal markers suggesting an amphisomal character. Point mutations in rabr-1 analogous to key residues of small GTPases suggest that rabr-1 functions in a GTP-bound form independently of GTPase activity. Taken together, rabr-1 encodes for an atypical small GTPase of the Rab-type that cell-nonautonomously restricts dendritic branching of somatosensory neurons, likely independently of GTPase activity., Competing Interests: Conflicts of interest The author(s) declare no conflict of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Genetics Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

It is well established that hearing loss can lead to widespread plasticity within the central auditory pathway, which is thought to contribute to the pathophysiology of audiological conditions such as tinnitus and hyperacusis. Emerging evidence suggests that hearing loss can also result in plasticity within brain regions involved in higher-level cognitive functioning like the prefrontal cortex; findings which may underlie the association between hearing loss and cognitive impairment documented in epidemiological studies. Using the 40-Hz auditory steady state response to assess sound-evoked gamma oscillations, we previously showed that noise-induced hearing loss results in impaired gamma phase coherence within the prefrontal but not the auditory cortex. To determine whether region-specific structural or molecular changes accompany this differential plasticity following hearing loss, in the present study we utilized Golgi-Cox staining to assess dendritic organization and synaptic density, as well as Western blotting to measure changes in synaptic signaling proteins in these cortical regions. We show that following noise exposure, impaired gamma phase coherence within the prefrontal cortex is accompanied by alterations in pyramidal cell dendritic morphology and decreased expression of proteins involved in GABAergic (GAD65) and glutamatergic (NR2B) neurotransmission; findings that were not observed in the auditory cortex, where gamma phase coherence remained unchanged post-noise exposure. In contrast to the noise-induced effects we observed in the prefrontal cortex, plasticity in the auditory cortex was characterized by an increase in NR2B suggesting increased excitability, as well as increases in the synaptic proteins PSD95 and synaptophysin within the auditory cortex. Overall, our results highlight the disparate effect of noise-induced hearing loss on auditory and higher-level brain regions as well as potential structural and molecular mechanisms by which hearing loss may contribute to impaired cognitive and sensory functions mediated by the prefrontal and auditory cortices., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Neurons form cell-type-specific morphologies that are shaped by cell-surface molecules and their cellular events governing dendrite growth. One growth rule is dendrite self-avoidance, whereby dendrites distribute uniformly within a neuron's territory by avoiding sibling branches. In mammalian neurons, dendrite self-avoidance is regulated by a large family of cell-recognition molecules called the clustered protocadherins (cPcdhs). Genetic and molecular studies suggest that the cPcdhs mediate homophilic recognition and repulsion between self-dendrites. However, this model has not been tested through direct investigation of self-avoidance during development. Here, we performed live imaging and four-dimensional (4D) quantifications of dendrite morphogenesis to define the dynamics and cPcdh-dependent mechanisms of self-avoidance. We focused on the mouse retinal starburst amacrine cell (SAC), which requires the gamma-Pcdhs (Pcdhgs) and self/non-self-recognition to establish a stereotypic radial morphology while permitting dendritic interactions with neighboring SACs. Through morphogenesis, SACs extend dendritic protrusions that iteratively fill the growing arbor and contact and retract from nearby self-dendrites. Compared to non-self-contacting protrusions, self-contacting events have longer lifetimes, and a subset persists as loops. In the absence of the Pcdhgs, non-self-contacting dynamics are unaffected but self-contacting retractions are significantly diminished. Self-contacting bridges accumulate, leading to the bundling of dendritic processes and disruption to the arbor shape. By tracking dendrite self-avoidance in real time, our findings establish that the γ-Pcdhs mediate self-recognition and retraction between contacting sibling dendrites. Our results also illustrate how self-avoidance shapes stochastic and space-filling dendritic outgrowth for robust pattern formation in mammalian neurons., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The abundance of unpaired multimodal single-cell data has motivated a growing body of research into the development of diagonal integration methods. However, the state-of-the-art suffers from the loss of biological information due to feature conversion and struggles with modality-specific populations. To overcome these crucial limitations, we here introduce scConfluence, a method for single-cell diagonal integration. scConfluence combines uncoupled autoencoders on the complete set of features with regularized Inverse Optimal Transport on weakly connected features. We extensively benchmark scConfluence in several single-cell integration scenarios proving that it outperforms the state-of-the-art. We then demonstrate the biological relevance of scConfluence in three applications. We predict spatial patterns for Scgn, Synpr and Olah in scRNA-smFISH integration. We improve the classification of B cells and Monocytes in highly heterogeneous scRNA-scATAC-CyTOF integration. Finally, we reveal the joint contribution of Fezf2 and apical dendrite morphology in Intra Telencephalic neurons, based on morphological images and scRNA., (© 2024. The Author(s).)

In developing brains, axons exhibit remarkable precision in selecting synaptic partners among many non-partner cells. Evolutionarily conserved teneurins are transmembrane proteins that instruct synaptic partner matching. However, how intracellular signaling pathways execute teneurins' functions is unclear. Here, we use in situ proximity labeling to obtain the intracellular interactome of a teneurin (Ten-m) in the Drosophila brain. Genetic interaction studies using quantitative partner matching assays in both olfactory receptor neurons (ORNs) and projection neurons (PNs) reveal a common pathway: Ten-m binds to and negatively regulates a RhoGAP, thus activating the Rac1 small GTPases to promote synaptic partner matching. Developmental analyses with single-axon resolution identify the cellular mechanism of synaptic partner matching: Ten-m signaling promotes local F-actin levels and stabilizes ORN axon branches that contact partner PN dendrites. Combining spatial proteomics and high-resolution phenotypic analyses, this study advanced our understanding of both cellular and molecular mechanisms of synaptic partner matching., Competing Interests: Declaration of interests L.L. is a member of the advisory board for Cell., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Anti-N-methyl D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder characterized by IgG antibodies targeting NMDAR. The prevalence is remarkably higher in women and some develop the condition during pregnancy. While immunotherapies have shown good outcomes for pregnant mothers and their infants, the impact on early neurodevelopment remains elusive. This study investigates the effects of anti-NMDAR antibody on the development of primary cortical cultures. Anti-NMDAR antibody was administered to the cultures at day in vitro 5 for the following 5 days to assess dendritic branching and arbor complexity, and at day in vitro 14 for measuring the expression of brain-derived neurotrophic factor (BDNF) and synaptic proteins. Immature cultured neurons treated with anti-NMDAR antibody exhibited impaired dendritic branching and arbor complexity. Interestingly, BDNF expression was unaffected in mature neurons. Additionally, GluN1 expression, a mandatory NMDAR subunit, was significantly reduced, while no significant alterations were observed in PSD-95, gephyrin and synaptophysin expression. These findings shed light on the structural and synaptic impacts of anti-NMDAR antibody on immature neurons, providing evidence for their consequences in early neuronal development., Competing Interests: The authors report no conflicts of interest in this work.

Multiple studies have shown that astrocytes in the medullary dorsal horn (MDH) play an important role in the development of pathologic pain. However, little is known about the structural reorganization of the peripheral astrocytic processes (PAP), the main functional part of the astrocyte, in MDH in neuropathic state. For this, we investigated the structural relationship between PAP and their adjacent presynaptic axon terminals and postsynaptic dendrites in the superficial laminae of the MDH using electron microscopical immunohistochemistry for ezrin, a marker for PAP, and quantitative analysis in a rat model of neuropathic pain following chronic constriction injury of the infraorbital nerve (CCI-ION). We found that, compared to controls, in rats with CCI-ION, (1) the number, % area, surface density, and volume fraction of ezrin-positive (+) PAP, as well as the fraction of synaptic edge apposed by ezrin + PAP and the degree of its coverage of presynaptic axon terminals and postsynaptic dendrites increased significantly, (2) these effects were abolished by administration of the mGluR5 antagonist 2-methyl-6-(phenylethynyl) pyridine (MPEP). These findings indicate that PAP undergoes structural reorganization around the central synapses of sensory afferents following nerve injury, suggest that it may be mediated by mGluR5, and may represent the structural basis for enhancing astrocyte-neuron interaction in neuropathic pain., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The expression of E-cadherin on Langerhans cells (LC) is required for adequate dendrite intercalation between epidermal keratinocytes. Upon disruption of epidermal homeostasis by tape stripping, E-cadherin competent LC extend dendrites reaching up to the epidermal surface, while E-cad deficient LC lack this ability., (© 2024 The Authors. European Journal of Immunology published by Wiley‐VCH GmbH.)

The polarized nature of neurons depends on their microtubule dynamics and orientation determined by both microtubule-stabilizing and destabilizing factors. The role of destabilizing factors in developing and maintaining neuronal polarity is unclear. We investigated the function of KLP-7, a microtubule depolymerizing motor of the Kinesin-13 family, in axon-dendrite compartmentalization using PVD neurons in Caenorhabditis elegans . Loss of KLP-7 caused a mislocalization of axonal proteins, including RAB-3, SAD-1, and their motor UNC-104, to dendrites. This is rescued by cell-autonomous expression of the KLP-7 or colchicine treatment, indicating the involvement of KLP-7-dependent microtubule depolymerization. The high mobility of KLP-7 is correlated to increased microtubule dynamics in the dendrites, which restricts the enrichment of UNC-44, an integral component of Axon Initial Segment (AIS) in these processes. Due to the loss of KLP-7, ectopic enrichment of UNC-44 in the dendrite potentially redirects axonal traffic into dendrites that include plus-end out microtubules, axonal motors, and cargoes. These observations indicate that KLP-7-mediated depolymerization defines the microtubule dynamics conducive to the specific enrichment of AIS components in dendrites. This further compartmentalizes dendritic and axonal microtubules, motors, and cargoes, thereby influencing neuronal polarity., Competing Interests: Conflict of interests: The authors declare no competing financial interests.

During animal development, the spatiotemporal properties of molecular events largely determine the biological outcomes. Conventional gene analysis methods lack the spatiotemporal resolution for precise dissection of developmental mechanisms. Although optogenetic tools exist for manipulating designer proteins in cultured cells, few have been successfully applied to endogenous proteins in live animals. Here, we report OptoTrap, a light-inducible clustering system for manipulating endogenous proteins of diverse sizes, subcellular locations, and functions in Drosophila . This system turns on fast, is reversible in minutes or hours, and contains variants optimized for neurons and epithelial cells. By using OptoTrap to disrupt microtubules and inhibit kinesin-1 in neurons, we show that microtubules support the growth of highly dynamic dendrites and that kinesin-1 is required for patterning of low- and high-order dendritic branches in differential spatiotemporal domains. OptoTrap allows for precise manipulation of endogenous proteins in a spatiotemporal manner and thus holds promise for studying developmental mechanisms in a wide range of cell types and developmental stages.

The processing of synaptic signals in somatodendritic compartments determines neuronal computation. Although the amplification of excitatory signals by local voltage-dependent cation channels has been extensively studied, their spatiotemporal dynamics in elaborate dendritic branches remain obscure owing to technical limitations. Using fluorescent voltage imaging throughout dendritic arborizations in hippocampal pyramidal neurons, we demonstrate a unique chloride ion (Cl - )-dependent remote computation mechanism in the distal branches. Excitatory postsynaptic potentials triggered by local laser photolysis of caged glutamate spread along dendrites, with gradual amplification toward the distal end while attenuation toward the soma. Tour de force subcellular patch-clamp recordings from thin branches complemented by biophysical model simulations revealed that the asymmetric augmentation of excitation relies on tetrodotoxin-resistant sodium ion (Na + ) channels and Cl - conductance accompanied by a more hyperpolarized dendritic resting potential. Together, this study reveals the cooperative voltage-dependent actions of cation and anion conductance for dendritic supralinear computation, which can locally decode the spatiotemporal context of synaptic inputs.

Biological and artificial neural networks learn by modifying synaptic weights, but it is unclear how these systems retain previous knowledge and also acquire new information. Here, we show that cortical pyramidal neurons can solve this plasticity-versus-stability dilemma by differentially regulating synaptic plasticity at distinct dendritic compartments. Oblique dendrites of adult mouse layer 5 cortical pyramidal neurons selectively receive monosynaptic thalamic input, integrate linearly, and lack burst-timing synaptic potentiation. In contrast, basal dendrites, which do not receive thalamic input, exhibit conventional NMDA receptor (NMDAR)-mediated supralinear integration and synaptic potentiation. Congruently, spiny synapses on oblique branches show decreased structural plasticity in vivo. The selective decline in NMDAR activity and expression at synapses on oblique dendrites is controlled by a critical period of visual experience. Our results demonstrate a biological mechanism for how single neurons can safeguard a set of inputs from ongoing plasticity by altering synaptic properties at distinct dendritic domains., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

In vertebrate retina, individual neurons of the same type are distributed regularly across the tissue in a pattern known as a mosaic. Establishment of mosaics during development requires cell-cell repulsion among homotypic neurons, but the mechanisms underlying this repulsion remain unknown. Here, we show that two mouse retinal cell types, OFF and ON starburst amacrine cells, establish mosaic spacing by using their dendritic arbors to repel neighboring homotypic somata. Using transgenic tools and single-cell labeling, we identify a developmental period when starburst somata are contacted by neighboring starburst dendrites; these serve to exclude somata from settling within the neighbor's dendritic territory. Dendrite-soma exclusion is mediated by MEGF10, a cell-surface molecule required for starburst mosaic patterning. Our results implicate dendrite-soma exclusion as a key mechanism underlying starburst mosaic spacing and raise the possibility that this could be a general mechanism for mosaic patterning across many cell types and species., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Human cortical neurons (hCNs) exhibit high dendritic complexity and synaptic density, and the maturation process is greatly protracted. However, the molecular mechanism governing these specific features remains unclear. Here, we report that the hominoid-specific gene TBC1D3 promotes dendritic arborization and protracts the pace of synaptogenesis. Ablation of TBC1D3 in induced hCNs causes reduction of dendritic growth and precocious synaptic maturation. Forced expression of TBC1D3 in the mouse cortex protracts synaptic maturation while increasing dendritic growth. Mechanistically, TBC1D3 functions via interaction with MICAL1, a monooxygenase that mediates oxidation of actin filament. At the early stage of differentiation, the TBC1D3/MICAL1 interaction in the cytosol promotes dendritic growth via F-actin oxidation and enhanced actin dynamics. At late stages, TBC1D3 escorts MICAL1 into the nucleus and downregulates the expression of genes related with synaptic maturation through interaction with the chromatin remodeling factor ATRX. Thus, this study delineates the molecular mechanisms underlying human neuron development., Competing Interests: Declaration of interests The authors have no competing financial interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

During neuronal pruning, phagocytes engulf shed cellular debris to avoid inflammation and maintain tissue homeostasis. How phagocytic receptors recognize degenerating neurites had been unclear. Here, we identify two glucosyltransferases Alg8 and Alg10 of the N-glycosylation pathway required for dendrite fragmentation and clearance through genetic screen. The scavenger receptor Draper (Drpr) is N-glycosylated with complex- or hybrid-type N-glycans that interact specifically with galectins. We also identify the galectins Crouching tiger (Ctg) and Hidden dragon (Hdg) that interact with N-glycosylated Drpr and function in dendrite pruning via the Drpr pathway. Ctg and Hdg are required in hemocytes for expression and function, and are induced during dendrite injury to localize to injured dendrites through specific interaction with exposed phosphatidylserine (PS) on the surface membrane of injured dendrites. Thus, the galectins Ctg and Hdg bridge the interaction between PS and N-glycosylated Drpr, leading to the activation of phagocytosis., (© 2024. The Author(s).)

Inhibitory circuits in the mammalian olfactory bulb (OB) dynamically reformat olfactory information as it propagates from peripheral receptors to downstream cortex. To gain mechanistic insight into how specific OB interneuron types support this sensory processing, we examine unitary synaptic interactions between excitatory mitral and tufted cells (MTCs), the OB projection neurons, and a conserved population of anaxonic external plexiform layer interneurons (EPL-INs) using pair and quartet whole-cell recordings in acute mouse brain slices. Physiological, morphological, neurochemical, and synaptic analyses divide EPL-INs into distinct subtypes and reveal that parvalbumin-expressing fast-spiking EPL-INs (FSIs) perisomatically innervate MTCs with release-competent dendrites and synaptically detonate to mediate fast, short-latency recurrent and lateral inhibition. Sparse MTC synchronization supralinearly increases this high-fidelity inhibition, while sensory afferent activation combined with single-cell silencing reveals that individual FSIs account for a substantial fraction of total network-driven MTC lateral inhibition. OB output is thus powerfully shaped by detonation-driven high-fidelity perisomatic inhibition., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Burton et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Most neurons are not replaced after injury and thus possess robust intrinsic mechanisms for repair after damage. Axon injury triggers a calcium wave, and calcium and cAMP can augment axon regeneration. In comparison to axon regeneration, dendrite regeneration is poorly understood. To test whether calcium and cAMP might also be involved in dendrite injury signaling, we tracked the responses of Drosophila dendritic arborization neurons to laser severing of axons and dendrites. We found that calcium and subsequently cAMP accumulate in the cell body after both dendrite and axon injury. Two voltage-gated calcium channels (VGCCs), L-Type and T-Type, are required for the calcium influx in response to dendrite injury and play a role in rapid initiation of dendrite regeneration. The AC8 family adenylyl cyclase, Ac78C, is required for cAMP production after dendrite injury and timely initiation of regeneration. Injury-induced cAMP production is sensitive to VGCC reduction, placing calcium upstream of cAMP generation. We propose that two VGCCs initiate global calcium influx in response to dendrite injury followed by production of cAMP by Ac78C. This signaling pathway promotes timely initiation of dendrite regrowth several hours after dendrite damage., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Hertzler et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

A compromised capacity to maintain NAD pools is recognized as a key underlying pathophysiological feature of neurodegenerative diseases. NAD acts as a substrate in major cell functions including mitochondrial homeostasis, cell signalling, axonal transport, axon/Wallerian degeneration, and neuronal energy supply. Dendritic degeneration is an early marker of neuronal stress and precedes cell loss. However, little is known about dendritic structural preservation in pathologic environments and remodelling in mature neurons. Retinal ganglion cell dendritic atrophy is an early pathological feature in animal models of the disease and has been demonstrated in port-mortem human glaucoma samples. Here we report that a nicotinamide (a precursor to NAD through the NAD salvage pathway) enriched diet provides robust retinal ganglion cell dendritic protection and preserves dendritic structure in a rat model of experimental glaucoma. Metabolomic analysis of optic nerve samples from the same animals demonstrates that nicotinamide provides robust metabolic neuroprotection in glaucoma. Advances in our understanding of retinal ganglion cell metabolic profiles shed light on the energetic shift that triggers early neuronal changes in neurodegenerative diseases. As nicotinamide can improve visual function short term in existing glaucoma patients, we hypothesize that a portion of this visual recovery may be due to dendritic preservation in stressed, but not yet fully degenerated, retinal ganglion cells., (© 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).)

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.)

Dendrite pathology and synaptic loss result in neural circuit dysfunction, a common feature of neurodegenerative diseases. There is a lack of strategies that target dendritic and synaptic regeneration to promote neurorecovery. We show that daily human recombinant insulin eye drops stimulate retinal ganglion cell (RGC) dendrite and synapse regeneration during ocular hypertension, a risk factor to develop glaucoma. We demonstrate that the ribosomal protein p70S6 kinase (S6K) is essential for insulin-dependent dendritic regrowth. Furthermore, S6K phosphorylation of the stress-activated protein kinase-interacting protein 1 (SIN1), a link between the mammalian target of rapamycin complexes 1 and 2 (mTORC1/2), is required for insulin-induced dendritic regeneration. Using two-photon microscopy live retinal imaging, we show that insulin rescues single-RGC light-evoked calcium (Ca 2+ ) dynamics. We further demonstrate that insulin enhances neuronal survival and retina-brain connectivity leading to improved optomotor reflex-elicited behaviors. Our data support that insulin is a compelling pro-regenerative strategy with potential clinical implications for the treatment and management of glaucoma.

A recently reported Schizophrenia-associated genetic variant in the 3'UTR of the human furin gene, a homolog of C. elegans kpc-1, highlights an important role of the furin 3'UTR in neuronal development. We isolate three kpc-1 mutants that display abnormal dendrite arborization in PVD neurons and defective male mating behaviors. We show that the kpc-1 3'UTR participates in dendrite branching and self-avoidance. The kpc-1 3'UTR facilitates mRNA localization to branching points and contact points between sibling dendrites and promotes translation efficiency. A predicted secondary structural motif in the kpc-1 3'UTR is required for dendrite self-avoidance. Animals with over-expression of DMA-1, a PVD dendrite receptor, exhibit similar dendrite branching and self-avoidance defects that are suppressed with kpc-1 over-expression. Our results support a model in which KPC-1 proteins are synthesized at branching points and contact points to locally down-regulate DMA-1 receptors to promote dendrite branching and self-avoidance of a mechanosensory neuron important for male courtship., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Shih et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The Drosophila RNA-binding protein (RBP) Nab2 acts in neurons to regulate neurodevelopment and is orthologous to the human intellectual disability-linked RBP, ZC3H14. Nab2 governs axon projection in mushroom body neurons and limits dendritic arborization of class IV sensory neurons in part by regulating splicing events in ∼150 mRNAs. Analysis of the Sex-lethal ( Sxl ) mRNA revealed that Nab2 promotes an exon-skipping event and regulates m 6 A methylation on Sxl pre-mRNA by the Mettl3 methyltransferase. Mettl3 heterozygosity broadly rescues Nab2 null phenotypes implying that Nab2 acts through similar mechanisms on other RNAs, including unidentified targets involved in neurodevelopment. Here, we show that Nab2 and Mettl3 regulate the removal of a 5'UTR (untranslated region) intron in the trio pre-mRNA. Trio utilizes two GEF domains to balance Rac and RhoGTPase activity. Intriguingly, an isoform of Trio containing only the RhoGEF domain, GEF2, is depleted in Nab2 null nervous tissue. Expression of Trio-GEF2 rescues projection defects in Nab2 null axons and dendrites, while the GEF1 Rac1-regulatory domain exacerbates these defects, suggesting Nab2-mediated regulation Trio-GEF activities. Collectively, these data indicate that Nab2-regulated processing of trio is critical for balancing Trio-GEF1 and -GEF2 activity and show that Nab2, Mettl3, and Trio function in a common pathway that shapes axon and dendrite morphology., Competing Interests: Conflict of interest: The authors declare no financial conflict of interest.

Dendrites are injured in a variety of clinical conditions such as traumatic brain and spinal cord injuries and stroke. How neurons detect injury directly to their dendrites to initiate a pro-regenerative response has not yet been thoroughly investigated. Calcium plays a critical role in the early stages of axonal injury detection and is also indispensable for regeneration of the severed axon. Here, we report cell and neurite type-specific differences in laser injury-induced elevations of intracellular calcium levels. Using a human KCNJ2 transgene, we demonstrate that hyperpolarizing neurons only at the time of injury dampens dendrite regeneration, suggesting that inhibition of injury-induced membrane depolarization (and thus early calcium influx) plays a role in detecting and responding to dendrite injury. In exploring potential downstream calcium-regulated effectors, we identify L-type voltage-gated calcium channels, inositol triphosphate signaling, and protein kinase D activity as drivers of dendrite regeneration. In conclusion, we demonstrate that dendrite injury-induced calcium elevations play a key role in the regenerative response of dendrites and begin to delineate the molecular mechanisms governing dendrite repair., 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 Authors. Published by Elsevier Ltd.. All rights reserved.)

The branched architecture of neuronal dendrites is a key factor in how neurons form ordered networks and discoveries continue to be made identifying proteins and protein-protein interactions that direct or execute the branching and extension of dendrites. Our prior work showed that the molecular scaffold Pdlim5 and delta-catenin, in conjunction, are two proteins that help regulate the branching and elongation of dendrites in cultured hippocampal neurons and do so through a phosphorylation-dependent mechanism triggered by upstream glutamate signaling. In this report we have focused on Pdlim5's multiple scaffolding domains and how each contributes to dendrite branching. The three identified regions within Pdlim5 are the PDZ, DUF, and a trio of LIM domains; however, unresolved is the intra-molecular conformation of Pdlim5 as well as which domains are essential to regulate dendritic branching. We address Pdlim5's structure and function by examining the role of each of the domains individually and using deletion mutants in the context of the full-length protein. Results using primary hippocampal neurons reveal that the Pdlim5 DUF domain plays a dominant role in increasing dendritic branching. Neither the PDZ domain nor the LIM domains alone support increased branching. The central role of the DUF domain was confirmed using deletion mutants in the context of full-length Pdlim5. Guided by molecular modeling, additional domain mapping studies showed that the C-terminal LIM domain forms a stable interaction with the N-terminal PDZ domain, and we identified key amino acid residues at the interface of each domain that are needed for this interaction. We posit that the central DUF domain of Pdlim5 may be subject to modulation in the context of the full-length protein by the intra-molecular interaction between the N-terminal PDZ and C-terminal LIM domains. Overall, our studies reveal a novel mechanism for the regulation of Pdlim5's function in the regulation of neuronal branching and highlight the critical role of the DUF domain in mediating these effects.

Neuronal anatomy is central to the organization and function of brain cell types. However, anatomical variability within apparently homogeneous populations of cells can obscure such insights. Here, we report large-scale automation of neuronal morphology reconstruction and analysis on a dataset of 813 inhibitory neurons characterized using the Patch-seq method, which enables measurement of multiple properties from individual neurons, including local morphology and transcriptional signature. We demonstrate that these automated reconstructions can be used in the same manner as manual reconstructions to understand the relationship between some, but not all, cellular properties used to define cell types. We uncover gene expression correlates of laminar innervation on multiple transcriptomically defined neuronal subclasses and types. In particular, our results reveal correlates of the variability in Layer 1 (L1) axonal innervation in a transcriptomically defined subpopulation of Martinotti cells in the adult mouse neocortex., (© 2024. The Author(s).)

Fast electrical signaling in dendrites is central to neural computations that support adaptive behaviors. Conventional techniques lack temporal and spatial resolution and the ability to track underlying membrane potential dynamics present across the complex three-dimensional dendritic arbor in vivo. Here, we perform fast two-photon imaging of dendritic and somatic membrane potential dynamics in single pyramidal cells in the CA1 region of the mouse hippocampus during awake behavior. We study the dynamics of subthreshold membrane potential and suprathreshold dendritic events throughout the dendritic arbor in vivo by combining voltage imaging with simultaneous local field potential recording, post hoc morphological reconstruction, and a spatial navigation task. We systematically quantify the modulation of local event rates by locomotion in distinct dendritic regions, report an advancing gradient of dendritic theta phase along the basal-tuft axis, and describe a predominant hyperpolarization of the dendritic arbor during sharp-wave ripples. Finally, we find that spatial tuning of dendritic representations dynamically reorganizes following place field formation. Our data reveal how the organization of electrical signaling in dendrites maps onto the anatomy of the dendritic tree across behavior, oscillatory network, and functional cell states., (© 2024. The Author(s).)

Neurons receive correlated levels of excitation and inhibition, a feature that is important for proper brain function. However, how this relationship between excitatory and inhibitory inputs is established during the dynamic period of circuit wiring remains unexplored. Using multiple techniques, including in utero electroporation, electron microscopy, and electrophysiology, we reveal a tight correlation in the distribution of excitatory and inhibitory synapses along the dendrites of developing CA1 hippocampal neurons. This correlation was present within short dendritic stretches (<20 μm) and, surprisingly, was most pronounced during early development, sharply declining with maturity. The tight matching between excitation and inhibition was unexpected, as inhibitory synapses lacked an active zone when formed and exhibited compromised evoked release. We propose that inhibitory synapses form as a stabilizing scaffold to counterbalance growing excitation levels. This relationship diminishes over time, suggesting a critical role for a subcellular balance in early neuronal function and circuit formation., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Basal dendrites of layer 5 cortical pyramidal neurons exhibit Na + and N-methyl-D-aspartate receptor (NMDAR) regenerative spikes and are uniquely poised to influence somatic output. Nevertheless, due to technical limitations, how multibranch basal dendritic integration shapes and enables multiplexed barcoding of synaptic streams remains poorly mapped. Here, we combine 3D two-photon holographic transmitter uncaging, whole-cell dynamic clamp, and biophysical modeling to reveal how synchronously activated synapses (distributed and clustered) across multiple basal dendritic branches are multiplexed under quiescent and in vivo-like conditions. While dendritic regenerative Na + spikes promote millisecond somatic spike precision, distributed synaptic inputs and NMDAR spikes regulate gain. These concomitantly occurring dendritic nonlinearities enable multiplexed information transfer amid an ongoing noisy background, including under back-propagating voltage resets, by barcoding the axo-somatic spike structure. Our results unveil a multibranch dendritic integration framework in which dendritic nonlinearities are critical for multiplexing different spatial-temporal synaptic input patterns, enabling optimal feature binding., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The brain can adapt to changes in the environment through alterations in the number and structure of synapses. During embryonic and early postnatal stages, the synapses in the brain undergo rapid expansion and interconnections to form circuits. However, many of these synaptic connections are redundant or incorrect. Neurite pruning is a conserved process that occurs during both vertebrate and invertebrate development. It requires precise spatiotemporal control of local degradation of cellular components, comprising cytoskeletons and membranes, refines neuronal circuits, and ensures the precise connectivity required for proper function. The Drosophila 's class IV dendritic arborization (C4da) sensory neuron has a well-characterized architecture and undergoes dendrite-specific sculpting, making it a valuable model for unravelling the intricate regulatory mechanisms underlie dendritic pruning. In this review, I attempt to provide an overview of the present state of research on dendritic pruning in C4da sensory neurons, as well as potential functional mechanisms in neurodevelopmental disorders.

In developing olfactory bulb (OB), mitral cells (MCs) remodel their dendrites to establish the precise olfactory circuit, and these circuits are critical for individuals to sense odors and elicit behaviors for survival. However, how microtubules (MTs) participate in the process of dendritic remodeling remains elusive. Here, we reveal that calmodulin-regulated spectrin-associated proteins (CAMSAPs), a family of proteins that bind to the minus-end of the noncentrosomal MTs, play a crucial part in the development of MC dendrites. We observed that Camsap2 knockout (KO) males are infertile while the reproductive tract is normal. Further study showed that the infertility was due to the severe defects of mating behavior in male mice. Besides, mice with loss-of-function displayed defects in the sense of smell. Furthermore, we found that the deficiency of CAMSAP2 impairs the classical morphology of MCs, and the CAMSAP2-dependent dendritic remodeling process is responsible for this defect. Thus, our findings demonstrate that CAMSAP2 plays a vital role in regulating the development of MCs., (© 2024. The Author(s).)

Introduction: The medial prefrontal cortex (mPFC) forms output pathways through projection neurons, inversely receiving adjacent and long-range inputs from other brain regions. However, how afferent neurons of mPFC are affected by chronic stress needs to be clarified. In this study, the effects of chronic restraint stress (CRS) on the distribution density of mPFC dendrites/dendritic spines and the projections from the cortex and subcortical brain regions to the mPFC were investigated., Methods: In the present study, C57BL/6 J transgenic (Thy1-YFP-H) mice were subjected to CRS to establish an animal model of depression. The infralimbic (IL) of mPFC was selected as the injection site of retrograde AAV using stereotactic technique. The effects of CRS on dendrites/dendritic spines and afferent neurons of the mPFC IL were investigaed by quantitatively assessing the distribution density of green fluorescent (YFP) positive dendrites/dendritic spines and red fluorescent (retrograde AAV recombinant protein) positive neurons, respectively., Results: The results revealed that retrograde tracing virus labeled neurons were widely distributed in ipsilateral and contralateral cingulate cortex (Cg1), second cingulate cortex (Cg2), prelimbic cortex (PrL), infralimbic cortex, medial orbital cortex (MO), and dorsal peduncular cortex (DP). The effects of CRS on the distribution density of mPFC red fluorescence positive neurons exhibited regional differences, ranging from rostral to caudal or from top to bottom. Simultaneously, CRS resulted a decrease in the distribution density of basal, proximal and distal dendrites, as well as an increase in the loss of dendritic spines of the distal dendrites in the IL of mPFC. Furthermore, varying degrees of red retrograde tracing virus fluorescence signals were observed in other cortices, amygdala, hippocampus, septum/basal forebrain, hypothalamus, thalamus, mesencephalon, and brainstem in both ipsilateral and contralateral brain. CRS significantly reduced the distribution density of red fluorescence positive neurons in other cortices, hippocampus, septum/basal forebrain, hypothalamus, and thalamus. Conversely, CRS significantly increased the distribution density of red fluorescence positive neurons in amygdala., Conclusion: Our results suggest a possible mechanism that CRS leads to disturbances in synaptic plasticity by affecting multiple inputs to the mPFC, which is characterized by a decrease in the distribution density of dendrites/dendritic spines in the IL of mPFC and a reduction in input neurons of multiple cortices to the IL of mPFC as well as an increase in input neurons of amygdala to the IL of mPFC, ultimately causing depression-like behaviors., Competing Interests: Declaration of Competing Interest The authors declare that there is no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Tripartite motif (TRIM46) is a relatively novel protein that belongs to tripartite motif family. TRIM46 organizes parallel microtubule arrays on the axons, which are important for neuronal polarity and axonal function. TRIM46 is highly expressed in the brain, but its biological function in adults has not yet been determined., Results: Trim46 knockout (KO) rat line was established using CRISPR/cas9. Trim46 KO rats had smaller hippocampus sizes, fewer neuronal dendritic arbors and dendritic spines, and shorter and more distant axon initial segment. Furthermore, the protein interaction between endogenous TRIM46 and FK506 binding protein 5 (FKBP5) in brain tissues was determined; Trim46 KO increased hippocampal FKBP5 protein levels and decreased hippocampal protein kinase B (Akt) phosphorylation, gamma-aminobutyric acid type A receptor subunit alpha1 (GABRA1) and glutamate ionotropic receptor NMDA type subunit 1 (NMDAR1) protein levels. Trim46 KO rats exhibited hypoactive behavioral changes such as reduced spontaneous activity, social interaction, sucrose preference, impaired prepulse inhibition (PPI), and short-term reference memory., Conclusions: These results demonstrate the significant impact of Trim46 KO on brain structure and behavioral function. This study revealed a novel potential association of TRIM46 with dendritic development and neuropsychiatric behavior, providing new insights into the role of TRIM46 in the brain., (© 2024 American Association for Anatomy.)

The Pcdhg gene cluster encodes 22 γ-Protocadherin (γ-Pcdh) cell adhesion molecules that critically regulate multiple aspects of neural development, including neuronal survival, dendritic and axonal arborization, and synapse formation and maturation. Each γ-Pcdh isoform has unique protein domains-a homophilically interacting extracellular domain and a juxtamembrane cytoplasmic domain-as well as a C-terminal cytoplasmic domain shared by all isoforms. The extent to which isoform-specific versus shared domains regulate distinct γ-Pcdh functions remains incompletely understood. Our previous in vitro studies identified protein kinase C (PKC) phosphorylation of a serine residue within a shared C-terminal motif as a mechanism through which γ-Pcdh promotion of dendrite arborization via myristoylated alanine-rich C-kinase substrate (MARCKS) is abrogated. Here, we used CRISPR/Cas9 genome editing to generate two new mouse lines expressing only non-phosphorylatable γ-Pcdhs, due either to a serine-to-alanine mutation (Pcdhg S/A ) or to a 15-amino acid C-terminal deletion resulting from insertion of an early stop codon (Pcdhg CTD ). Both lines are viable and fertile, and the density and maturation of dendritic spines remain unchanged in both Pcdhg S/A and Pcdhg CTD cortex. Dendrite arborization of cortical pyramidal neurons, however, is significantly increased in both lines, as are levels of active MARCKS. Intriguingly, despite having significantly reduced levels of γ-Pcdh proteins, the Pcdhg CTD mutation yields the strongest phenotype, with even heterozygous mutants exhibiting increased arborization. The present study confirms that phosphorylation of a shared C-terminal motif is a key γ-Pcdh negative regulation point and contributes to a converging understanding of γ-Pcdh family function in which distinct roles are played by both individual isoforms and discrete protein domains., (© 2024 The Author(s). Developmental Neurobiology published by Wiley Periodicals LLC.)

The function of medial entorhinal cortex layer II (MECII) excitatory neurons has been recently explored. MECII dysfunction underlies deficits in spatial navigation and working memory. MECII neurons comprise two major excitatory neuronal populations, pyramidal island and stellate ocean cells, in addition to the inhibitory interneurons. Ocean cells express reelin and surround clusters of island cells that lack reelin expression. The influence of reelin expression by ocean cells and interneurons on their own morphological differentiation and that of MECII island cells has remained unknown. To address this, we used a conditional reelin knockout (RelncKO) mouse to induce reelin deficiency postnatally in vitro and in vivo. Reelin deficiency caused dendritic hypertrophy of ocean cells, interneurons and only proximal dendritic compartments of island cells. Ca2+ recording showed that both cell types exhibited an elevation of calcium frequencies in RelncKO, indicating that the hypertrophic effect is related to excessive Ca2+ signalling. Moreover, pharmacological receptor blockade in RelncKO mouse revealed malfunctioning of GABAB, NMDA and AMPA receptors. Collectively, this study emphasizes the significance of reelin in neuronal growth, and its absence results in dendrite hypertrophy of MECII neurons., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

N-methyl-d-aspartate receptors (NMDARs) at hippocampal excitatory synapses undergo a late postnatal shift in subunit composition, from an initial prevalence of GluN2B subunit incorporation to a later predominance of GluN2A. This GluN2B to GluN2A shift alters NMDAR calcium conductance dynamics and intracellular molecular signaling that are individually regulated by distinct GluN2 signaling domains and temporally align with developmental alterations in dendritic and synaptic plasticity. However, the impacts of individual GluN2B to GluN2A signaling domains on neuronal development remain unknown. Ionotropic and intracellular signaling domains of GluN2 subunits were separated by creating chimeric GluN2 subunits that were expressed in two transgenic mouse lines. Western blot and immunoprecipitation revealed that roughly one third of native synaptic NMDARs were replaced by transformed NMDARs without altering total synaptic NMDAR content. Schaffer collateral synaptic strength was transiently increased in acutely prepared hippocampal slices at just over 3 weeks of age in animals overexpressing the GluN2B carboxy terminus. Long-term potentiation (LTP) induction following lower frequency stimulation was regulated by GluN2 ionotropic signaling domains in an age-dependent manner and LTP maintenance was enhanced by overexpression of the GluN2B CTD in mature animals. After higher frequency stimulation, the induction and maintenance of LTP were increased in young adult animals overexpressing the GluN2B ionotropic signaling domains but reduced in juveniles just over 3 weeks of age. Confocal imaging of green fluorescent protein (GFP)- labeled CA1 pyramidal neurons revealed no alterations in dendritic morphology or spine density in mice expressing chimeric GluN2 subunits. These results illustrate how individual GluN2 subunit signaling domains do or do not control physiological and morphological development of hippocampal excitatory neurons and better clarify the neurobiological factors that govern hippocampal maturation. SIGNIFICANCE STATEMENT: A developmental reduction in the magnitude of hippocampal long-term synaptic potentiation (LTP) and a concomitant improvement in spatial maze performance coincide with greater incorporation of GluN2A subunits into synaptic NMDARs. Corroborating our prior discovery that overexpression of GluN2A-type ionotropic signaling domains enables context-based navigation in immature mice, GluN2A-type ionotropic signaling domain overexpression reduces LTP induction threshold and magnitude in immature mice. Also, we previously found that GluN2B carboxy terminal domain (CTD) overexpression enhances long-term spatial memory in mature mice and now report that the GluN2B CTD is associated with greater amplitude of LTP after induction in mature mice. Thus, the late postnatal maturation of context encoding likely relies on a shift toward GluN2A-type ionotropic signaling and a reduction in the threshold to induce LTP while memory consolidation and LTP maintenance are regulated by GluN2B subunit CTD signaling., (© 2024 Wiley Periodicals LLC.)

Fluorescence recovery after photobleaching (FRAP) is a laser method of light microscopy to evaluate the rapid movement of fluorescent molecules. To have a more reliable approach to analyze data from FRAP, we designed Fraping, a free access R library to data analysis obtained from FRAP. Unlike other programs, Fraping has a new form of analyzing curves of FRAP using statistical analysis based on the average curve difference. To evaluate our library, we analyzed the differences of actin polymerization in real time between dendrites and secondary neurites of cultured neuron transfected with LifeAct to track F-actin changes of neurites. We found that Fraping provided greater sensitivity than the conventional model using mobile fraction analysis. Likewise, this approach allowed us to normalize the fluorescence to the size area of interest and adjust data curves choosing the best parametric model. In addition, this library was supplemented with data simulation to have a more significant enrichment for the analysis behavior. We concluded that Fraping is a method that reduces bias when analyzing two data groups as compared with the conventional methods. This method also allows the users to choose a more suitable analysis approach according to their requirements. RESEARCH HIGHLIGHTS: Fraping is a new programming tool to analyze FRAP data to normalize fluorescence recovery curves. The conventional method uses one-point analysis, and the new one compares all the points to define the similarity of the fluorescence recovery., (© 2024 The Authors. Microscopy Research and Technique published by Wiley Periodicals LLC.)

The development of cell-type-specific dendritic arbors is integral to the proper functioning of neurons within their circuit networks. In this study, we examine the regulatory relationship between the cytosolic chaperonin CCT, key insulin pathway genes, and an E3 ubiquitin ligase (Cullin1) in dendritic development. CCT loss of function (LOF) results in dendritic hypotrophy in Drosophila Class IV (CIV) multi-dendritic larval sensory neurons, and CCT has recently been shown to fold components of the TOR (Target of Rapamycin) complex 1 (TORC1) in vitro. Through targeted genetic manipulations, we confirm that an LOF of CCT and the TORC1 pathway reduces dendritic complexity, while overexpression of key TORC1 pathway genes increases the dendritic complexity in CIV neurons. Furthermore, both CCT and TORC1 LOF significantly reduce microtubule (MT) stability. CCT has been previously implicated in regulating proteinopathic aggregation, thus, we examine CIV dendritic development in disease conditions as well. The expression of mutant Huntingtin leads to dendritic hypotrophy in a repeat-length-dependent manner, which can be rescued by Cullin1 LOF. Together, our data suggest that Cullin1 and CCT influence dendritic arborization through the regulation of TORC1 in both health and disease.

Recombinant adeno-associated viruses (AAVs) allow rapid and efficient gene delivery to the nervous system, are widely used in neuroscience research, and are the basis of FDA-approved neuron-targeting gene therapies. Here we find that an innate immune response to the AAV genome reduces dendritic length and complexity and disrupts synaptic transmission in mouse somatosensory cortex. Dendritic loss is apparent 3 weeks after injection of experimentally relevant viral titers, is not restricted to a particular capsid serotype, transgene, promoter, or production facility, and cannot be explained by responses to surgery or transgene expression. AAV-associated dendritic loss is accompanied by a decrease in the frequency and amplitude of miniature excitatory postsynaptic currents and an increase in the proportion of GluA2-lacking, calcium-permeable AMPA receptors. The AAV genome is rich in unmethylated CpG DNA, which is recognized by the innate immunoreceptor Toll-like receptor 9 (TLR9), and acutely blocking TLR9 preserves dendritic complexity and AMPA receptor subunit composition in AAV-injected mice. These results reveal unexpected impacts of an immune response to the AAV genome on neuronal structure and function and identify approaches to improve the safety and efficacy of AAV-mediated gene delivery in the nervous system., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Since the days of Ramón y Cajal, the vast diversity of neuronal and particularly dendrite morphology has been used to catalog neurons into different classes. Dendrite morphology varies greatly and reflects the different functions performed by different types of neurons. Significant progress has been made in our understanding of how dendrites form and the molecular factors and forces that shape these often elaborately sculpted structures. Here, we review work in the nematode Caenorhabditis elegans that has shed light on the developmental mechanisms that mediate dendrite morphogenesis with a focus on studies investigating ciliated sensory neurons and the highly elaborated dendritic trees of somatosensory neurons. These studies, which combine time-lapse imaging, genetics, and biochemistry, reveal an intricate network of factors that function both intrinsically in dendrites and extrinsically from surrounding tissues. Therefore, dendrite morphogenesis is the result of multiple tissue interactions, which ultimately determine the shape of dendritic arbors., Competing Interests: Conflicts of interest. The author(s) declare no conflict of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Genetics Society of America.)