Glioma pathophysiology is robustly regulated by interactions with neurons. Key to these interactions is the role of neuroligin-3 (NLGN3), a synaptic adhesion molecule shed in response to neuronal activity that functions as a paracrine factor crucial for glioma growth. Here we elucidate the mechanistic pathway whereby shed NLGN3 interacts with glioma and their normal glial counterparts. NLGN3 binds to chondroitin sulfate proteoglycan 4 (CSPG4, also known as NG2) on both glioma and healthy oligodendrocyte precursor cells (OPCs), facilitating CSPG4 shedding by ADAM10. NLGN3-CSPG4 interactions alter membrane tension, thereby activating mechanotransducers, primarily PIEZO1, leading to membrane depolarization and subsequent ADAM10-mediated CSPG4 shedding. The NLGN3-CSPG4-PIEZO1 pathway maintains OPCs in an undifferentiated, stem-like state and promotes glioma proliferation, underscoring its dual roles in healthy and malignant contexts.

Psychedelic drugs, such as lysergic acid diethylamide and psilocybin, have emerged as potentially transformative therapeutics for various neuropsychiatric conditions, including depression, anxiety, post-traumatic stress disorder, migraine and cluster headaches. Classical psychedelics exert their effects through activation of 5-hydroxytryptamine 2A receptors (HTR2As). Here we provide a suite of engineered mice that will be useful for clarifying the role of HTR2A in psychedelic drug actions. We generated Htr2aEGFP-CreERT2 mice to identify both HTR2A-EGFP-CT receptors and HTR2A-containing cells, thereby revealing HTR2A distribution in the brain. We also generated humanized Htr2aA242S-EGFP-Cre and constitutive Htr2aCre mice. Psychedelic-induced behavioral changes in these mice validated their utility for these studies. Electrophysiological investigations on brain sections from these mice revealed that 2,5,-dimethoxy-4-iodoamphetamine induced robust increases in firing of genetically identified pyramidal neurons. These mouse lines are valuable tools for investigating the molecular, cellular, pharmacological, physiological, behavioral and other mechanisms of psychedelic actions in vivo.

The insular cortex has become an increasingly important focus of neuroscientific research because of its broad involvement in psychological and behavioral processes and its dysfunction in neuropsychiatric, developmental, degenerative and metabolic disorders. The insula is easily imaged in the human brain and is also a key target for both fundamental and translational studies in nonhuman animals. However, owing to a dearth of truly comparative studies on the insula, the extent to which this region shares structural and functional homologies between humans, monkeys and rodents remains incompletely understood. Here, we systematically evaluate current knowledge regarding homologies in the insula among model species and humans. We examine the strengths and limitations of various laboratory species for investigating the insula, and discuss how these factors influence the interpretation of findings and their application to the human insula. Finally, we propose research directions aimed at strengthening translational insula research and enhancing our understanding of cross-species similarities and differences.

The mossy fiber (MF) connections to pyramidal cells in hippocampal CA3 are thought to participate in pattern separation, pattern completion and memory encoding, yet no large-scale neuronal wiring diagram exists for these connections. We assembled a 3D electron microscopy volume (~1 × 1 × 0.1 mm[3]) from mouse hippocampal CA3. By proofreading and automated segmentation, we reconstructed and classified all soma-containing neurons-including 1,815 pyramidal cells and 229 inhibitory cells-and over 55,000 MF axons. Pyramidal cells receive more numerous MF inputs along a proximodistal gradient. Some distal cells show surprisingly high convergence via relatively small terminals with fewer vesicles. Pyramidal cells share significantly more MF inputs than networks randomized by degree-preserving swap and are better approximated by networks randomized by proximity-preserving swap. We identify a feedforward inhibitory circuit motif from MFs via perisomatic interneurons that selectively target a pyramidal subtype. We demonstrated large-scale mapping across levels in the hippocampus-from circuits to cell types to vesicles. The dataset is shared through Pyr.ai , an online platform for hippocampal connectomics.

G-protein-coupled receptor-based fluorescent sensors are widely used to correlate neuromodulatory signaling with brain function. Although experiments in transfected cells often reveal selectivity for individual neurotransmitters, sensor specificity in the brain frequently remains uncertain. Using imaging in mouse brains, we find that norepinephrine and dopamine cross-activate the respective sensors. Non-specific activation occurred when innervation of the cross-reacting transmitter was high, and silencing of specific innervation was indispensable for interpreting sensor fluorescence.

Compositionality has long been regarded as a uniquely human capacity and a cornerstone of general intelligence. It is most clearly exemplified in natural language, where a finite set of words is combined through grammatical rules to generate an unbounded number of sentences. Recent advances across disciplines challenge the view that compositionality is exclusive to human cognition and question whether an explicit symbolic structure is required to implement it. Large language models, for example, achieve impressive compositional abilities through scale alone. Neuroscience has also revealed that animals use compositional neural codes when applying knowledge to novel situations, while theory and modeling are beginning to clarify how neural networks without explicit symbolic structures implement compositional computations. High-density neural recordings from animals performing compositional tasks, combined with reverse engineering of neural network models, now enable us to test fundamental questions, such as how biological brains implement compositional solutions and when compositional behavior can emerge from scale rather than from explicit compositional mechanisms. We propose that compositional mechanisms exist along a continuum defined by the expressivity of computation-specific building blocks and the complexity of systematic recombination rules. Comparing implementations across biological and artificial systems will determine whether general intelligence requires explicit compositionality or can emerge from scaled mechanisms alone.

Stem-cell-based in vitro models offer promising potential to elucidate human brain cell functions and interactions, but limitations in reproducibility, maturation and cell-type diversity persist. Especially, prolonged incorporation of mature microglia and studies of neuroinflammation have proven challenging. Here, we developed a human induced pluripotent stem cell-based three-dimensional cortical brain tissue model (3BTM) containing neurons, astrocytes and microglia with high reproducibility, maturity and viability. 3BTMs show morphological, functional and proteomic maturation of all cell types, leading to high similarity to their in vivo counterparts. Incorporated microglia survive for over 6 months and display mature morphology, functions and gene expression. Importantly, when engineered to model Alzheimer's disease pathology, 3BTMs recapitulate key disease hallmarks, including amyloid deposition, increased phospho-tau levels and neuroinflammation, with microglia shifting their transcriptional landscape to disease-relevant signatures. Treatment of Alzheimer's disease 3BTMs with anti-Aβ immunotherapy cleared deposits and largely reversed disease signatures in glia. Together, our microglia-containing model provides a platform for studying physiological and pathological states of human brain tissue.

Brain computation depends on intricately connected yet highly distributed neural networks. Owing to the absence of the requisite technologies, causally testing fundamental hypotheses on inter-areal processing has remained largely out of reach. Here, we developed a two-photon holographic mesoscope capable of simultaneously reading and writing neural activity patterns with near-single-cell resolution across large regions of the mouse cortex. We demonstrate the precise photoactivation of spatial and temporal sequences of neurons in one or multiple cortical areas while reading out the downstream effects in several other regions. Thus, we have established mesoscale two-photon holographic optogenetics as a platform for mapping functional connectivity and causal interactions across distributed cortical areas with high resolution.

The cerebral cortex depends on a diverse repertoire of inhibitory neurons, yet how this diversity emerges during development remains unclear. Rare inhibitory subtypes are often underrepresented in single-cell RNA-sequencing datasets, limiting resolution of their developmental trajectories. Here we developed a computational pipeline to enrich and integrate rare cell types across datasets and applied it to somatostatin-expressing (SST[+]) inhibitory neurons, the most diverse inhibitory class in cortex. We generated Dev-SST-v1 and Dev-SST-v2, transcriptomic reference maps comprising more than 55,000 mouse SST[+] neurons. These maps identify three major SST[+] inhibitory neuron groups-Martinotti cells (MCs), non-Martinotti cells (nMCs) and long-range projecting (LRP) neurons-each defined by a distinct developmental strategy. MCs commit early, whereas nMCs diversify progressively. LRPs follow a contracting trajectory, with one transient subtype eliminated by programmed cell death. Together, these findings establish three distinct modes of SST[+] inhibitory neuron diversification, including a previously unrecognized contracting mode.

Myelin sheaths comprise compacted layers of membrane wrapped around axons. Each sheath, if 'unwrapped', has a cytoplasm-filled space at its perimeter. Transmission electron microscopy reveals that this space contains microtubules and organelles; however, whether these are developmental remnants or serve a specific function remains unknown. Live imaging of myelinating oligodendrocytes in mice showed microtubule-dependent organelle transport within myelin sheath cytoplasmic spaces. Further, movement of myelin-located peroxisomes was modulated by neuronal electrical activity, in vitro and in vivo. Loss of oligodendroglial KIF21B and/or CNP in vivo led to the apparent stasis of myelin organelles and secondary axon pathology. We, thus, propose the acronym TRAM (transport route across myelin), defining the continuous cytoplasmic network in oligodendrocytes and myelin. This system, comprising the inner and outer tongues and paranodal loops, spans compact myelin and enables transport of metabolites and organelles between the oligodendrocyte soma and the periaxonal space.