Wiley: Glia: Table of Contents

Organization of Astrocytic GLT‐1 at Cortical Inhibitory Synapses

Marcello Melone, Michael Di Palma, Annalisa Scimemi, Fiorenzo Conti — Sun, 07 Jun 2026 21:39:00 -0700

GLT-1+ ALs frequently juxtapose symmetric synapses. Distance-based phenotyping identifies symmetric- and asymmetric-associated GLT-1+ ALs. Distal inhibitory synapses show enriched GLT-1/α2 couples in ALs within 1000 nm, conserved in human cortex.

ABSTRACT

Glutamate spillover from excitatory synapses modulates neighboring inhibitory synapses, yet the ultrastructural organization of the major glutamate transporter GLT-1 at these sites remains poorly defined. Using quantitative pre-embedding electron microscopy in rat and human cortex, we found that GLT-1-positive astrocytic leaflets (ALs) were frequently juxtaposed to morphologically identified symmetric synapses, with similar prevalence across axo-somatic, proximal axo-dendritic, and distal axo-dendritic subtypes. Because inhibitory synapses are embedded in a dense excitatory neuropil, we applied distance-based phenotyping relative to the nearest asymmetric synapse to define symmetric-associated GLT-1+ ALs. Within this population, distal axo-dendritic symmetric synapses showed shorter AL-to-synaptic-edge distances and were embedded in a tighter local excitatory microenvironment. Post-embedding immunogold further showed that GLT-1 was enriched at the plasma membranes of ALs and localized extrasynaptically relative to symmetric synapses. Consistently, symmetric-associated membrane GLT-1 and closely spaced GLT-1/α2 couples (with an interdistance ≤ 50 nm) were preferentially localized within 1000 nm of distal symmetric synapses compared to proximal. Similar organizational features of membrane GLT-1/α2 couples were observed in human cortex. These findings identify a subtype-dependent extrasynaptic astrocytic GLT-1 organization at cortical inhibitory synapses and provide a morphological framework for glutamate-dependent modulation of inhibitory signaling.

Female Mice Show Stronger Time‐of‐Day Modulation of Astrocytic Ca2+ Activity in the Sleep‐Regulatory Ventrolateral Preoptic Nucleus

Sun, 07 Jun 2026 21:34:59 -0700

VLPO astrocytes exhibit sex-specific Ca²⁺ dynamics across the nycthemeral cycle. Males show faster Ca²⁺ kinetics, while females display increased amplitude, frequency, and network coupling at Zeitgeber Time (ZT)-14. Sex is a key variable in astrocyte-based sleep regulation mechanisms.

ABSTRACT

Astrocytes actively contribute to sleep regulation through intracellular calcium (Ca²⁺) signaling. Yet, whether astrocytic dynamics within sleep-promoting hypothalamic nuclei vary across the nycthemeral cycle in a sex-dependent manner remains unknown. The ventrolateral preoptic area (VLPO) is a key sleep-promoting nucleus whose neuronal circuitry has been extensively characterized. However, the local astrocytic Ca²⁺ activity remains poorly defined. Here, we investigated astrocytic Ca²⁺ signaling in the VLPO of male and female mice across the nycthemeral cycle. Using two-photon Ca²⁺ imaging in acute VLPO-containing brain slices prepared at Zeitgeber Time (ZT)-2, corresponding to the onset of the rest period, and ZT-14, corresponding to the beginning of the active period, we combined single-event analyses with graph-based network approaches to characterize astrocytic activity across scales. At the level of individual events, spontaneous astrocytic Ca²⁺ dynamics exhibited marked state dependence and sexual dimorphism. In males, Ca²⁺ events were smaller and faster at ZT-14 than at ZT-2 (shorter duration and accelerated rise and decay time). In contrast, in females, ZT-14 was characterized by increased event amplitude and frequency, consistent with upregulated Ca²⁺ signaling during the active phase. At the network level, functional connectivity remained stable in males. Conversely, females exhibited robust network remodeling at ZT-14, including increased astrocyte recruitment, higher node degree of correlations, and a marked rise in the number and proportion of highly connected astrocytes. Together, these findings reveal sex-specific astrocytic signaling strategies in the VLPO across the nycthemeral cycle and underscore the need to incorporate sex as a biological variable in astrocyte-based sleep research.

Sustained Neuronal Stimulation Activates Paraventricular Thalamus Astrocytes for Chronicity of Neuropathic Pain in Mice

Tue, 02 Jun 2026 22:55:11 -0700

Neuron–astrocyte interactions drive supraspinal astrocyte reactivity in chronic neuropathic pain, where astrocytic Kir4.1 in the PVT regulates pain progression, and reactive PVT astrocytes promote hyperalgesia through PVT–mPFC projections.

ABSTRACT

Current treatments for chronic neuropathic pain are limited in efficacy, partly due to the complicated etiology of neuropathic pain chronicity. Ongoing nociceptive inputs from peripheral injuries lead to maladaptive alterations in the central nervous system during the transition from acute to chronic pain, which in turn contribute to the maintenance of chronic pain and reduce the effectiveness of peripheral analgesics. Reactive astrocytes are known to contribute to chronic neuropathic pain in the spinal cord, while how astrocytes contribute to chronic pain in supraspinal nuclei remains unclear. This study reveals that continuous painful stimulation from peripheral injury induces astrocyte reactivity and downregulation of astrocytic Kir4.1 (inward rectifying potassium channel protein 4.1) in the paraventricular thalamus (PVT). In turn, these reactive astrocytes help to maintain neuronal hyperactivity in the PVT and enhance neural projections from PVT to the medial prefrontal cortex (mPFC), which contribute to hyperalgesia in chronic neuropathic pain. Therefore, this study identifies a neuro-glial interaction that mediates chronic pain in supraspinal brain.

Issue Information

Mon, 01 Jun 2026 21:49:05 -0700

Glia, Volume 74, Issue 8, August 2026.

Molecular Characterization and Immune Modulation of Schwann Cells in Vestibular Schwannoma

Lu Wang, Yijiang Bai, Guowei Li, Ye He, Guodong Tang, Xuewen Wu — Mon, 01 Jun 2026 21:46:11 -0700

Single-cell profiling identifies a Schwann-4 subpopulation with MHC-II and PI3K-focal adhesion features, where elevated CTSZ suggests PVR-TIGIT-mediated Treg modulation in vestibular schwannoma.

ABSTRACT

Vestibular schwannoma (VS) is a benign tumor originating from the vestibular nerve, and its complex tumor microenvironment presents significant challenges for research. This study employs single-cell transcriptome sequencing to comprehensively investigate the molecular characteristics of Schwann cells within VS and their potential immunoregulatory roles in the tumor microenvironment. We identified a novel subpopulation of Schwann cells, termed Schwann 4, which shows significantly expressed MHC class II molecules and co-enrichment of PI3K signaling, focal adhesion, and cell adhesion-related pathways, suggesting its potential involvement in tumor-immune modulation. Utilizing machine learning models, we pinpointed 179 genes significantly expressed in Schwann 4, with CTSZ emerging as a candidate gene. CTSZ expression is elevated in VS and is significantly correlated with the PI3K pathway. Comparative analysis revealed that CTSZ promotes proliferation in malignant CNS tumors, whereas its role in benign VS appears distinct. Experimental analysis revealed that CTSZ is correlated with regulatory T cells (Tregs) functionality markers via the PVR-TIGIT pathway, suggesting a potential mechanism for Schwann cell-mediated immune modulation. Functional assays further demonstrated that CTSZ knockdown impairs cell migration and focal adhesion kinase activity. Drug sensitivity analyses identified candidate agents such as YM201636 and AT7867, though their applicability to VS requires dedicated validation. This study contributes to understanding the molecular mechanisms of Schwann cells in benign nerve sheath tumors while providing preliminary evidence for future therapeutic investigation.

Sphingosine‐1‐Phosphate Receptor 1 Regulates Competition Dependent Astrocyte Morphogenesis and Tiling in Murine Cortex

Mon, 01 Jun 2026 21:45:28 -0700

Neuronal contact-induced expression of S1PR1 in astrocytes is regulated by JAK-STAT3 signaling. Astrocytic S1PR1 modulates cortical astrocyte morphogenesis. Astrocytic S1PR1 regulates astrocyte territorial overlap/tiling in a competition dependent manner.

ABSTRACT

Astrocytes are highly abundant in the mammalian brain and coordinate with neurons and other glial cells to regulate neural circuit structure, function, and blood–brain barrier integrity among many to maintain proper brain homeostasis. Astrocytes perform most of these functions owing to their highly complex morphologies and hundreds of thousands of fine processes that are important in contacting neuronal synapses and other glial cells. In fact, the morphological complexity of astrocytes is regulated by the presence and activity of neurons and helps establish astrocyte territory/tiling in a nonoverlapping pattern; however, the mechanisms of astrocyte tiling are not well characterized. Using a human astrocyte-mouse neuron coculture system, we previously showed that sphingosine-1-phosphate receptor 1 (S1PR1) regulates astrocyte morphogenesis in a neuronal contact dependent manner. In this study, we find that S1PR1 regulates astrocyte morphogenesis in vivo. Using astrocyte-specific S1PR1 knockout mouse models and adeno-associated viral labeling methods, we show that S1PR1 is crucial in establishing competition driven astrocyte tiling and morphogenesis in the developing brain. Furthermore, we show that JAK-STAT3 signaling regulates neuronal contact induced expression of S1PR1 in cocultured astrocytes. These studies therefore uncover a lipid signaling receptor as a major regulator of astrocyte morphogenesis and tiling in murine cortical layers.