RhoA is well known as a key molecular switch for cytoskeleton remodeling, and previous studies reveal RhoA plays a pivotal role in Schwann cell myelination which is highly dependent on the dynamics regulation of the actin and microtubule cytoskeleton. Existing evidence indicates RhoA modulates myelination and other biofunctions by targeting actin filament turnover; however, the role of RhoA in microtubule dynamics remains unknown. Herein, Bulk mRNA sequencing and bioinformatic analysis enriched microtubule dynamics-related ontology terms in RhoA knockout Schwann cells, and identified that microtubules contribute to RhoA deficiency-caused hypomyelination. Both invivo and invitro experiments demonstrated that genetic ablation or pharmacological inhibition of RhoA attenuates microtubule dynamics in Schwann cells, whereas activated RhoA overexpression or RhoA agonist enhances the microtubule dynamics. RhoA conditional knockout (cKO) in Schwann cells led to hypomyelination, dysmyelination and nerve functional deficits in mice. Mechanistically, the present study identified CDK2 as a crucial mediating molecule for RhoA regulating microtubule dynamics. CDK2 overexpression could reverse the reduced microtubule dynamics, hypomyelination and motor deficits in RhoA cKO mice. Furthermore, RhoA modulating CDK2 is dependent on YAP/TEAD signaling, and the ASPM/p60-Katanin axis mediates the role of CDK2 in controlling microtubule dynamics. Collectively, this study uncovered a novel RhoA/YAP1/TEAD3/CDK2/ASPM/p60-Katanin axis in regulating microtubule dynamics during Schwann cell myelination, which indicates that this pathway may be utilized as new targets for repairing congenital hypomyelination/dysmyelination neuropathy or peripheral nerve injury.

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) are age-related disorders with similar pathological features, particularly insulin resistance and chronic inflammation. However, the primary drivers of insulin resistance in the AD brain remain debated. Although astrocytes and their metabolic functions have been increasingly implicated in AD, their specific role in brain insulin resistance is still unclear. In this study, we excluded peripheral metabolic confounders and focused on the alterations during a narrow time window surrounding amyloid-β (Aβ) plaque deposition in J20 mice. As Aβ pathology progressed, we observed a reduction in astrocyte numbers with increased morphological complexity. Furthermore, transcriptomic profiling demonstrated altered gene expression at synaptic, glial, and metabolic levels, along with a general suppression of insulin signaling pathways that indicated insulin resistance. Notably, we found a significant downregulation of serum and glucocorticoid-inducible kinase 1 (SGK1) and upregulation of insulin receptor substrate 2 (IRS2) expression, which diverged from the classic pattern observed in peripheral insulin resistance. We also detected a contradictory cytokine pattern in T-helper 17, where interleukin (IL)-6 and IL-17 levels were decreased in the hippocampus but elevated in the serum. This opposing trajectory suggests that astrocyte dysfunction and SGK1 downregulation have a critical role in immune signaling imbalance. Taken together, these findings highlight astrocyte depletion and/or dysfunction as key drivers of brain-specific insulin resistance and immune dysregulation in early AD, and that metabolic impairments in AD have a central nervous system-specific nature distinct from that in T2DM.

Neuroinflammation mediated by microglia and astrocytes is a major component of traumatic brain injury (TBI) pathophysiology. The sterile alpha and TIR motif containing 1 (SARM1) protein has been identified to play a key role in neurodegeneration and inflammatory cascades. Therefore, we hypothesized that the inhibition of SARM1 would prevent glial reactivity following TBI and could be targeted for therapeutic intervention. TBI was modeled in wild type (WT) and SARM1 knock-out (SARM1-KO) mice of both biological sexes by midline fluid percussion injury. At 7 or 28 days post-injury, brains were collected to examine glial reactivity via immunohistochemistry and compared to naïve controls. The density of microglia and glial fibrillary acidic protein (GFAP) immunoreactivity of astrocytes was significantly increased across time post-injury. Furthermore, microglial morphological changes and increased colocalization with a surrogate marker of phagocytosis (CD68) were evident at 7 days post-injury. In the absence of SARM1, microglial density and colocalization with CD68 was greater compared with WT animals, regardless of TBI. However, there were no differences in GFAP immunoreactivity with the genetic deletion of SARM1. When investigating biological sexes, the TBI-induced increase in microglial density and cell volume was greater in male mice at 7 days post-injury; however, microglia were more deramified in females. There were no significant differences in GFAP immunoreactivity between male and female mice. These results indicate that the genetic deletion of SARM1 is not sufficient to alter GFAP-labeling of astrocytes; however, SARM1 appears to impact microglial density and CD68 colocalization in the naïve and injured brain.

Chemogenetic strategies such as Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) enable precise manipulation of cell signaling. While previous studies have demonstrated that excitatory DREADDs modulate Ca2+ signaling and excitability in neurons and astrocytes, their role within the oligodendrocyte lineage remained unexplored. In this study, we utilized the hM3Dq receptor to examine how excitatory DREADDs modulate Ca2+ dynamics and oligodendrocyte biology, and to evaluate their potential for regulating oligodendrocyte development and function across both developmental and adult stages of the brain. Utilizing Cre-mediated recombination, the hM3Dq receptor was selectively expressed within the oligodendrocyte lineage. Activation of hM3Dq in oligodendrocytes induces the release of Ca2+ from internal stores and increases Ca2+ influx mediated by voltage-gated and glutamate channels. Invitro, hM3Dq activity promoted oligodendrocyte progenitor cell (OPC) proliferation and reduced oligodendrocyte maturation and myelin protein synthesis. Invivo, hM3Dq activation in NG2- or Sox10-positive oligodendrocytes during early postnatal development significantly delayed the myelination process, reduced the density of mature oligodendrocytes, and increased the number of proliferating OPCs in several brain areas. In contrast, hM3Dq activation in mature oligodendrocytes induced myelin loss and oligodendrocyte apoptotic cell death in the adult brain. RNA sequencing of hM3Dq-expressing OPCs revealed transcriptional changes in genes regulating cell cycle progression, potassium channel activity, and p53-associated signaling, along with disruptions in oligodendrocyte maturation programs. These findings demonstrate that chemogenetic modulation of intracellular signaling and Ca2+ dynamics via DREADDs provides a powerful tool to dissect and control oligodendrocyte development, with implications for understanding and treating myelin-related disorders.

Astrocytes are now widely accepted as key regulators of brain function and behavior. Calcium (Ca2+) signals in perisynaptic astrocytic processes (PAPs) enable astrocytes to fine-tune neurotransmission at tripartite synapses. As most PAPs are below the diffraction limit, their content in Ca2+ stores and the contribution of the latter to astrocytic Ca2+ activity is unclear. Here, we reconstruct hippocampal tripartite synapses in 3D from a high-resolution electron microscopy (EM) dataset and find that 75% of PAPs contain some endoplasmic reticulum (ER), a major calcium store in astrocytes. The ER in PAPs displays strikingly diverse shapes and intracellular spatial distributions. To investigate the causal relationship between each of these geometrical properties and the spatiotemporal characteristics of Ca2+ signals, we implemented an algorithm that generates 3D PAP meshes by altering the distribution of the ER independently from ER and cell shape. Reaction-diffusion simulations in these meshes reveal that astrocyte activity is governed by a complex interplay between the location of Ca2+ channels, ER surface-volume ratio, and spatial distribution. In particular, our results suggest that ER-PM contact sites can act as local signal amplifiers if equipped with IP3R clusters but attenuate PAP Ca2+ activity in the absence of clustering. This study sheds new light on the ultrastructural basis of the diverse astrocytic Ca2+ microdomain signals and on the mechanisms that regulate neuron-astrocyte signal transmission at tripartite synapses.

Injury to the central nervous system (CNS) such as spinal cord results in multifaceted cellular responses, including the glial scars, a structural formation of reactive glia around an area of severe tissue damage. However, the functional heterogeneity within the cells in glial scars remains unclear. In this study, we found Aldh1L1 lineage cells exhibited reactive astrocyte distribution, culminating in glial scar formation via proliferation and differentiation after SCI. Interestingly, the Aldh1L1+ glial scars were distinct from the GFAP+ glial scars, encircled an area closer to the injury center and harbored scattered Aldh1L1 lineage cells within the central zone. At day 7 after SCI, Aldh1L1 lineage cells reached peak activation; some of them exhibited an injury responsive intermediate state with neural stem cell-like properties, and a significant portion of the Aldh1L1+ glial scar arose from the differentiation and migration of central canal ependymal cells, not derived from invading meningeal cell lineages or pial astroglia. Some of the Aldh1L1+ cells in glial scar exhibited expression of oligodendrocyte progenitor cell markers. Mechanistically, YAP was highly expressed and activated in Aldh1L1+ cells after SCI, and YAP deletion in Aldh1L1+ cells inhibited glial scar formation and differentiation into astrocytes from Aldh1L1+ ependymal cells, exacerbated neuronal loss, and inhibited the functional recovery of mice after SCI. These results suggest that Aldh1L1 lineage cells contribute to the functional heterogeneity within the cells in glial scars after SCI and uncover the pivotal role of YAP signaling in the formation of glial scars derived from Aldh1L1 lineage cells.

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by the degeneration of motor neurons. However, the surrounding glia, including oligodendrocytes, also exhibit ALS pathology and TDP-43 related dysfunction. Given that oligodendrocytes, the myelinating cells of the central nervous system, are essential for motor neuron function, they may play an underappreciated role in ALS. Here, we have extensively characterized the oligodendrocyte lineage and myelin integrity in the TDP-43Q331K mouse model of ALS. In the lumbar spinal cord of end-stage male TDP-43Q331K mice (TDP-43), compared to wild-type littermates (WT), oligodendrocyte precursor cell (OPC) density, oligodendrocyte proliferation, and differentiation were all increased. There was no correlative increase in the density of mature oligodendrocytes, which was determined to be due to an increase in oligodendroglial apoptosis. In end-stage mice, myelin reflectance was increased in the dorsal column of TDP-43 mice, while electron microscopy showed myelin damage and misfolding in the TDP-43 mice. Our data suggest that the oligodendrocyte lineage is impacted in TDP-43 related ALS.