Ulcerative colitis (UC) patients experience cycles of active gut inflammation and remission, with neuropsychiatric comorbidities persisting even during clinical remission. While the dextran sulfate sodium (DSS) mouse model was previously applied to study gut-brain interactions, those studies focused on acute protocols missing the chronic, relapsing-remitting nature of human UC, when patients continue to experience central nervous system symptoms. Thus, we employed a chronic DSS treatment regimen comprising three cycles of active intestinal inflammation followed by remission phases to investigate region-specific microglial dynamics and their functional consequences on neuronal synapses. Transient blood-brain barrier alteration was detected during active chronic inflammation that was resolved during remission. Cortical microglia exhibited sustained iNOS-enriched activation state during remission, which coincided with synaptic imbalance: VGLUT1+ glutamatergic synaptosomes increased significantly in remission, while VGAT+ GABAergic vesicles declined, alongside suppressed neuronal c-fos expression. Hippocampal microglia adopted an ARG1-dominant phenotype with enriched TREM2, P2Y12R, and F4/80 expression during remission, indicating a phagocytic, reparative state. Hippocampal synaptosome analysis revealed selective excitatory enhancement with preserved inhibitory markers. Morphological analysis confirmed region-specific remodeling: cortical microglia displayed delayed process elaboration during remission, while hippocampal responses varied from transient (CA1) to persistent (CA3) somatic hypertrophy. These findings establish that remission from peripheral inflammation does not fully restore brain immune homeostasis. Persistent, region-specific microglial reactivity with cortical pro-inflammatory states associated with synaptic dysfunction and hippocampal adaptive responses preserving circuit integrity provides a mechanistic understanding for neuropsychiatric comorbidities in UC and suggests that brain-targeted therapies may be required to address the full disease burden.
Microglia are central mediators of neuroinflammation following ischemic stroke. Our previous multi-omics data revealed significant upregulation of leukocyte immunoglobulin-like receptor subfamily B member 4 (LILRB4) in microglia after transient middle cerebral artery occlusion (tMCAO), but its functional role remains unclear. This study demonstrates that LILRB4 expression peaks at 3 days post-tMCAO and is predominantly localized to microglia. Microglia-specific Lilrb4 knockout (Lilrb4-cKO) displayed worse neurological functions, larger infarct volumes, and more significant microglial activation. Transcriptomic analysis in vitro and functional experiments further revealed that microglial LILRB4 knockdown promoted the release of proinflammatory factors and enhanced necroptosis. Mechanistically, deletion of LILRB4 mainly drives receptor-interacting protein 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) expression and phosphorylation, without affecting receptor-interacting protein 1 (RIPK1). Pharmacologic inhibition of RIPK3 can relieve the brain damage caused by LILRB4 knockout after stroke. Additional analysis showed that LILRB4 negatively regulates the stimulator of interferon genes (STING)/RIPK3 axis to limit microglial necroptosis. STING suppression blocked the hyperactivation of RIPK3 induced by LILRB4 deficiency. In conclusion, LILRB4 attenuates ischemic brain injury by suppressing STING/RIPK3-mediated microglial necroptosis and neuroinflammation, emphasizing its significance as a potential neuroprotective therapy.
Multiple sclerosis (MS) is an autoimmune neurodegenerative disease characterized by immune-mediated attacks on myelin produced by oligodendrocytes (OLs). Oligodendrocyte precursor cells (OPCs) and mature OLs are CNS cell types essential for generating myelin sheath, which supports saltatory conduction and neuronal metabolic support. Although the roles of CNS resident cells (neurons, microglia, astrocytes) and peripheral immune cells in MS pathogenesis are well established, our understanding of how oligodendrocyte lineage cells (OLCs)-comprising OPCs and mature OLs-bidirectionally interact with these cell types to influence disease progression remains incomplete. Emerging evidence emphasizes the critical role of disease-associated OLCs in neuroimmune responses and their underlying signaling mechanisms. Therefore, elucidating how pathological environments shaped by CNS and peripheral cells influence OLC function may identify critical therapeutic targets for promoting remyelination and recovery in MS. This review synthesizes current knowledge of OLC biology in health and disease, with emphasis on complex intercellular interactions that determine demyelination, remyelination, and axonal integrity in MS.
Microglia are innate immune cells of the central nervous system (CNS). They extend their processes and migrate toward injuries in vivo. However, how the fractalkine receptor (CX3CR1) influences microglial migration remains unknown. Label-free proteomic profiling predicted changes in Ras homology family (RHO)-signaling activity that hint at dysregulated cytoskeleton signaling in Cx3cr1-deficient murine cortex tissue. To further investigate microglial migration, we carried out two-photon in vivo imaging at 4-h intervals for 72 h after a laser lesion in the cortex. Cx3cr1-deficient microglia showed enhanced migration toward the lesion. Additionally, the length and velocity of microglial fine processes extending toward the lesion were increased in Cx3cr1-deficient microglia. Migration remained unchanged in Ccr2-deficient mice, indicating that monocyte-derived macrophages/microglia did not contribute to microglia accumulation around the lesion. These results demonstrate that CX3CR1 modulates microglia migration toward laser-induced CNS injury. Manipulating microglia migration via the CX3CR1 signaling axis is therefore a potential target for the treatment of CNS injury.
Myelinogenesis is insufficient in numerous myelin-related diseases in the CNS, leading to functional impairments. Myelinogenesis couples with angiogenesis to ensure adequate need of oxygen and nutrients for oligodendrocyte (OL) differentiation. However, approaches to synchronize myelino-vascular coupling remain unavailable. We hypothesize the identification of shared signaling pathways in vascular cells and oligodendroglia may yield novel strategies to promote myelin repair through strengthening the blood vessel-myelination coupling. Here, single-cell sequencing and in situ hybridization revealed high expression of G-protein-coupled receptor 30 (Gpr30) in both vascular cells and oligodendroglia, with selective enrichment in pericytes and oligodendrocyte precursor cells (OPCs). Cell-specific deletion of GPR30 in pericytes driven by PDGFRβCreERT2 resulted in enhanced angiogenesis and myelination in developing brains. GPR30 deletion in OPCs or antagonizing GPR30 by G15 resulted in increased MBP-positive cell density and enhanced nanofiber wrapping capacity in vitro, thereby demonstrating an inhibiting role of GPR30 on OPC differentiation. To elucidate the coordinative role of GPR30 in both cell types, we employed NG2CreERT to induce a conditional knockout of GPR30 in both NG2-positive pericytes and OPCs. The conditional deletion of GPR30 enhanced myelination and increased vascular density in developing brains. Further, GPR30 cKO or G15 treatment enhanced myelin repair and functional recovery in the chronic neonatal hypoxia and lysolecithin-induced demyelination model, suggesting that antagonizing GPR30 is a promising strategy to synchronize angiogenesis with myelination to promote myelinogenesis. These findings establish GPR30 antagonism as a promising approach to enhance myelin repair through synchronizing pericyte-mediated angiogenesis and OPC differentiation.
Chronic stress induces psychiatric disorders, including depression and anxiety, yet effective therapies remain limited. Myelin in adult brains undergoes dynamic remodeling through oligodendrocyte precursor cells (OPCs) differentiation into oligodendrocytes (OLs) and the degeneration of pre-existing myelin. However, how chronic stress alters myelin dynamics and whether this represents a therapeutic target remains unclear. Here, adult mice subjected to 4-h daily restraint for 2 weeks exhibited significant anxiety, depression, and social deficits. Histological examinations revealed reduced OPC and OL density, decreased c-Fos-positive neurons, and loss of synaptic proteins in the brains exposed to chronic stress. To understand the dynamic changes of myelin, cell-lineage labeling and tracing demonstrated that chronic stress exposure remarkably inhibited oligodendrogenesis in the medial prefrontal cortex (mPFC), motor cortex, hippocampus, and amygdala, as revealed by the NG2CreERT; Tau-mGFP line, but did not significantly change pre-existing myelin as revealed by a newly generated line for mature OLs and myelin. To explore the role of myelinogenesis changes, adult myelin formation was inhibited by Olig2 conditional knockout in OPCs, resulting in decreased neuronal synaptic proteins and activity, accompanied by anxiety and depressive-like behaviors. Conversely, enhancing myelinogenesis through conditional deletion of the M1R in OPCs of stressed mice resulted in higher number of c-Fos-positive neurons, elevated synaptic protein expression, and a partial reversal of the behavioral deficits. Importantly, treating the stressed animal with the pro-myelination drug clemastine phenocopied the effects of M1R deletion on histological and behavioral disorders. Together, our findings demonstrate that enhancing oligodendrogenesis represents a promising strategy to rescue CRS-caused behavioral disorders.
Post-stroke recovery remains limited despite advances in acute reperfusion therapies, underscoring the need to better understand underlying mechanisms that shape repair. Microglia, the resident immune cells of the central nervous system, orchestrate responses to ischemic injury and critically influence neurovascular remodeling, axonal reorganization, and functional recovery. Emerging evidence indicates that inflammatory preconditioning can reprogram microglial responses to subsequent insults, yet the exact intracellular signaling pathways mediating this adaptive state remain incompletely defined. Here, we used a chemogenetic approach to selectively activate Gq signaling in microglia employing a microglia-specific DREADD mouse model. This strategy mimics Gq-coupled receptor activation in microglia in the absence of peripheral immune engagement. Pre-ischemic Gq activation significantly reduced infarct sizes at 24 h after experimental stroke in female mice and at 7 days in both sexes. Morphological analyses revealed that Gq-conditioned microglia exhibited increased structural complexity, adopting a highly ramified, spatially compact phenotype and higher CD68 expression, indicating increased phagocytic activity. Transcriptional profiling demonstrated that Gq activation primes autophagy-related defense pathways in microglia, resulting in upregulation of interferon-stimulated genes 7 days after stroke in both sexes. Together, our findings identify Gq signaling as a key modulatory pathway capable of reprogramming microglial phenotype and enhancing stroke recovery. These results highlight the plasticity of microglial signaling networks and support targeted modulation of microglial Gq pathways.
Microglia play a key role in the pathophysiology of Alzheimer's Disease (AD) and their increased heterogeneity likely affects disease progression. We previously identified distinct microglial signatures that were enriched in AD donors and associated with amyloid and tau, respectively. Here we generated a snRNAseq dataset from postmortem control and AD cases and analyzed alterations in cell-cell communication pathways that might be relevant to AD pathophysiology. One signaling pathway perturbed in AD cases involved SPP1, and while this pathway was also present in control samples, microglia-microglia SPP1 signaling was restricted to AD donors. Further analyses within microglia-microglia signaling predict AD-specific induction of GAS6-AXL signaling (from inflammatory and ribosomal microglia), and SPP1-ITGAV/ITGB5 signaling (from disease-associated and inflammatory microglia, among others). Together, these findings might in part explain the increased microglia phagocytic profile described in AD. RNAscope confirmed enrichment of SPP1 expressing microglia near amyloid plaques in AD brain tissue samples. These data indicate altered cellular communications between microglia in the AD brain.
Structural tissue alterations in numerous brain disorders can initiate mechanosensory signaling pathways and influence neuropathology. Astrocytes are highly mechanosensitive cells that play essential roles in maintaining brain homeostasis; however, the molecular mechanisms underlying astrocyte mechanosensation during pathological conditions remain largely unexplored. In this study, we investigated how the expression of the mechanosensitive ion channel Piezo1 in astrocytes is modulated by inflammatory triggers. We found that direct exposure of primary astrocyte cultures to inflammatory stimuli, including lipopolysaccharide (LPS) or oligomeric amyloid-β (oAβ), had minimal impact on astrocytic Piezo1 expression. In contrast, when LPS or oAβ were applied to primary microglia cultures, Piezo1 expression was increased in microglia, and conditioned media from these microglia cultures significantly upregulated Piezo1 expression in astrocytes. We further identified that microglia released pro-inflammatory cytokines (IL-1α, IL-1β, and TNF-α) that can directly enhance Piezo1 expression and Piezo1-mediated Ca2+ signaling in both rodent and human astrocytes. Microglial depletion in 5xFAD mice consistently and substantially reduced astrocytic Piezo1 expression in vivo, supporting the physiological relevance of this microglia-astrocyte signaling axis during pathology. Activation of Piezo1 with Yoda2 did not alter astrocytic inflammatory gene expression under basal conditions but reduced TNF-α, CCL2, and C3 expression following cytokine pretreatment. Conversely, Piezo1 knockdown increased GFAP expression at baseline and enhanced pro-inflammatory gene expression under cytokine stimulation, indirectly promoting microglial activation. These findings demonstrate that astrocytic Piezo1 expression is regulated by microglia-derived inflammatory signals and plays a context-dependent role in modulating astrocyte reactivity and neuroinflammatory responses.
Schwann cells (SC) are responsible for myelination in the peripheral nervous system (PNS). Myelin allows saltatory transmission of action potentials along axons and functionally relies on its unique constitution. We previously reported that Cdk7, a regulator of cell cycle progression and transcription, regulates myelin gene expression in oligodendrocytes and contributes to myelin maintenance in the central nervous system. Using mice with conditional Cdk7 knock-out in SCs, we provide evidence that Cdk7 is dispensable for myelin initiation but needed for the correct myelin thickness of larger caliber fibers in young mice, as well as for myelin elongation and rapid nerve conduction throughout age. We report that Cdk7 loss results in disturbed myelin stoichiometry, with significant dysregulation of lipid-related genes in SCs and a reduction in myelin protein zero. Finally, we demonstrate that Rxrγ, a nuclear receptor involved in lipid metabolism, is significantly downregulated in the absence of Cdk7. However, although Cdk7 regulates myelin segment length, our results indicate that this effect occurs independently of Rxrγ in myelinating dorsal root ganglion explants.
G protein-coupled receptor (GPCR) heteromerization represents a key organizational mechanism in cell signaling, but it remains difficult to determine, in native cells, how receptor-associated signals are distributed between non-interacting and heteromer-associated states. Here, we address this limitation by combining proximity ligation assay (PLA) with the newly applied MolBoolean methodology, enabling in situ quantification of the partitioning of adenosine A2A and cannabinoid CB2 receptor-associated signals between non-interacting fractions and A2A-CB2 heteromeric complexes in primary microglia. We show that resting microglia contain detectable A2A-CB2 heteromers together with a substantial non-interacting A2A-associated signal fraction. Selective activation of either receptor promotes redistribution of the detectable receptor-associated signal toward the heteromer-associated fraction. Ligand-induced redistribution also occurred in HEK-293T cells expressing the two receptors. In contrast, pro-inflammatory activation of primary microglia with LPS/IFN-γ markedly changes the basal organization of the receptor system, increasing the proportion of MolBoolean-detectable signal associated with A2A-CB2 complexes, with approximately 70% of the detectable receptor-associated signal corresponding to heteromeric complexes. In this inflammatory context, further agonist-induced repartitioning is strongly limited compared with that observed in resting microglia. These findings identify inflammation-dependent receptor partitioning as a quantitatively measurable feature of microglial A2A and CB2 receptor organization and provide a framework for interpreting how receptor context may influence future studies of A2A-CB2 pharmacology under neuroinflammatory conditions.
Sensory neurons express extrasynaptic GABAA receptors in their soma and axon, tonically activated by ambient GABA, modulating their excitability. However, the specific glial or neuronal origin of endogenous GABA that modulates this excitability has yet to be identified. We investigated the expression and function of enzymes involved in GABA synthesis via the ornithine-putrescine and glutamic acid pathways, and the effects of inhibiting these enzymes on the compound action potential (cAP) of primary afferent fibers. PCR analysis revealed that the dorsal root ganglia (DRG) express transcripts for ornithine decarboxylase (ODC), monoamine oxidase B (MAOB), diamine oxidase (DAO), and GAD65/67. Immunofluorescence assays confirmed the expression of ODC, MAOB, DAO, and GAT-3 proteins, as well as GABA in satellite glial cells (SGC). In contrast, neurons express DAO and ODC. However, despite the presence of GAD65 and GAD67 mRNAs, their corresponding proteins were not detected. Inhibition of ODC and MAOB, but not DAO or GAD, prevented the accumulation of GABA induced by the GABA transaminase (GABA-T) inhibitor aminooxy acetic acid in SGC cultures. Additionally, the Best1 channel blocker CaCCinh suppressed the K+-induced release of [3H]GABA in DRG and SGC cultures. Blocking GABAA receptors with picrotoxin, inhibiting MAOB, and blocking Best1 all increased cAP. However, allylglycine, a GAD inhibitor, failed to elicit this effect. Likewise, the use of selegiline and CaCCinh on cAP occluded the effects of picrotoxin. These results support that GABA synthesized and released by satellite glial cells activates extrasynaptic GABAA receptors, thereby modulating the excitability of sensory neurons.
Temporal lobe epilepsy (TLE), the most common form of adult focal epilepsy, is highly resistant to current medical therapy. Cytokine signaling, including via tumor necrosis factor-alpha (TNFα), has been implicated not only as an accompanying factor but as a key aspect in the initiation of the disease. TNFα, through its type-1 receptor (TNFR1) in astrocytes, controls excitatory circuits in the hippocampus, yet it remains unknown whether this astrocyte pathway specifically contributes to epilepsy. Here, we used a conditional cell-specific knockout mouse line to induce TNFR1 deletion selectively in astrocytes and test its roles in the initiation and progression of TLE. Mice lacking astrocyte TNFR1 showed decreased basal spectral power, longer latency to first seizure following treatment with kainic acid, and a less severe phenotype up to 4 weeks later. Thus, abrogation of astrocyte TNFR1 signaling may be beneficial in TLE and could provide a new therapeutic target for this disease.
Microglial dysfunction and aberrant lipid metabolism are emerging as key contributors to Parkinson's disease (PD) pathogenesis. However, the specific role and regulation of lipid droplets (LDs) within microglia remain poorly defined. In this study, we employed MPTP- and LPS-induced PD mouse models and an in vitro system utilizing astrocyte-conditioned medium to model disease-relevant lipid stress and found enhanced LD accumulation in microglia. VPS35 expression was decreased in microglia, correlating with elevated microglial LD levels in PD mouse models. We then performed genetic manipulations (knockdown and overexpression) of VPS35, including the PD-associated D620N mutant, in primary microglia and assessed LD accumulation, phagocytic function, inflammatory responses, and integrated stress pathways. We showed that VPS35 knockdown exacerbated the accumulation of LDs in microglia. Conversely, VPS35 overexpression ameliorated LD formation, improved phagocytic function, and reduced inflammatory and integrated stress responses in microglia. The PD-related VPS35[D620N] mutation abolished these protective effects. We further found that VPS35 interacts with Rab7 to maintain lysosomal function, and the D620N mutation disrupts this interaction, leading to defective LD clearance. Our findings reveal VPS35 dysfunction as a key pathogenic mechanism in PD, where the D620N mutation disrupts microglial lipid handling to promote disease progression, thereby nominating VPS35 restoration as a promising therapeutic strategy.
Astrocytes, known for their support roles, are emerging as active participants in synaptic plasticity and cognitive functions. Astrocytes actively regulate synaptic plasticity and memory through dynamic volume transients. Our previous research identified several key molecules, including TREK-1, TRPA1, and Best1 ion channels, as well as the gliotransmitter BDNF, as critical components of astrocytic volume transients. However, the precise mechanisms by which these volume transients influence synaptic plasticity and memory remain poorly understood. In this study, we investigate the roles of TREK-1 and TRPA1 in astrocytic volume dynamics and their downstream effects. Our findings, based on intrinsic optical signal imaging, electrophysiology, and behavioral assays, support a model in which neuronal stimulation induces astrocytic swelling, initiated by K+ uptake through TREK-1 channels and regulated by Ca2+ influx via TRPA1 channels. This swelling is closely associated with short- and long-term potentiation (LTP), and exogenous BDNF restores LTP under conditions of calcium sequestration during astrocytic calcium clamping experiments. Disruption of ion channels associated with astrocytic volume transients leads to significant impairments in spatial memory, as demonstrated by deficits in object-place recognition and passive avoidance tasks. Moreover, these channels contribute to the regulation of synaptic plasticity. These findings implicate astrocytic volume transients and BDNF as pivotal modulators of synaptic plasticity and memory, as well as potential therapeutic targets for addressing memory dysfunctions.
Astrocytes play a pivotal role in neuronal network development. Despite the well-known role of astrocytes in the pathophysiology of neurologic disorders, the utilization of induced pluripotent stem cell (iPSC)-derived astrocytes in neuronal networks remains limited. Here, we present a streamlined one-step protocol for the differentiation of iPSCs directly into functional astrocytes without the need for ectopic gene expression or neural progenitor cell generation. We found that culturing iPSCs directly in commercial astrocyte medium, was sufficient to differentiate iPSCs into functional astrocytes within 5 weeks. More than 60 iPSC lines were successfully differentiated into astrocytes by independent researchers across 10 independent laboratories. Validation of the iPSC-astrocyte cultures demonstrated consistent astrocyte differentiation with minimal batch-to-batch variability. In dept. characterization of a subset of iPSC lines confirmed astrocyte identity and functionality of the iPSC-astrocyte monocultures by immunofluorescence, flow cytometry, RNA sequencing, glutamate uptake assays and calcium signaling recordings. Optimization of the protocol enabled co-culture of iPSC-astrocytes with Ngn2 iPSC-derived neurons (iNeurons), promoting neuronal differentiation and synapse formation. Lastly, we used single-cell electrophysiology and multi-electrode arrays, by four independent researchers, to confirm robust neuronal network development in 5-week-old iPSC-astrocyte and iNeuron co-cultures. This protocol offers a rapid and efficient method to establish all-human astrocyte-neuron co-cultures, facilitating the investigation of cell-type-specific contributions to disease pathogenesis. Its validation across numerous iPSC lines in 10 independent laboratories highlights the reproducibility of the protocol and positions it as a platform for advancing disease modeling in human neural networks.
Astrocytes play essential roles in brain function and disorders. Yet, compared to neurons, our knowledge of the physiological and pathological signaling mechanisms in astrocytes remains limited. As a major challenge, the ultrathin (~10-100 nm) processes of astrocytes render high-throughput quantitative molecular imaging within well-defined cellular contexts very difficult. Here, we introduce a single-molecule localization microscopy-based methodology that achieves unprecedented resolution of the intricate astrocytic arbor in intact brain circuits. Postnatal tagging of the plasma membrane by electroporation in mice resulted in selective and sparse labeling of hippocampal astrocytes and enabled the complete visualization of individual astrocytes with nanoscale precision by using STochastic Optical Reconstruction Microscopy (STORM). We also developed high-yield and easy-to-implement approaches to segment, measure, analyze, and visualize nanoscale molecular information within astrocytic compartments. As a proof-of-concept, we could readily differentiate between synaptic and astrocytic proteins by using dual-color STORM super-resolution imaging. Moreover, we identified cell-type-specific differences in the distribution of monoacylglycerol lipase (MAGL), an enzyme regulating synaptic plasticity in neurons and coupling endocannabinoid signaling to prostaglandin signaling in astrocytes. Our findings demonstrate the feasibility of nanoscale molecular measurements within ultrathin astrocytic processes. Moreover, the results provide insights into the synapse-independent nanoscale arrangement of the astrocytic MAGL pool that controls neuroinflammatory processes.
Neonatal hypoxic injury is a common disorder that disrupts white matter development in preterm newborns, with long-term impacts on cognitive and mental function. While oxygen availability controls oligodendrocyte (OL) differentiation, prolonged hypoxia leads to OL death and impairs subsequent myelination even after returning to normoxic conditions. In this study, we uncovered the detrimental roles of the serine/threonine kinase CK2α and the transcriptional factor Bclaf1 in OL survival under hypoxic conditions. Phosphorylated Bclaf1 by CK2α drives hypoxia-mediated OL apoptosis, which can be reversed by introducing the hypoxia-inducible E3 ligase Vhl. Additionally, acute treatment with the clinically approved CK2 inhibitor silmitasertib and the herbal supplement curcumin not only reduces CK2α-Bclaf1 activity but also protects OLs and restores pre-myelinating ability in newborns following hypoxic injury. This approach unveils a key molecular regulation in hypoxia-related OL pathology and highlights a potential therapeutic strategy to mitigate neonatal hypoxic injury and prevent mental health complications.
In the mammalian cerebellum, three types of astroglial cells-Bergmann glial cells (BGs), inner granule cell layer (IGL) astrocytes, and white matter (WM) astrocytes-arise in postnatal timing from two types of progenitors: Bergmann glia-like progenitors (BGLPs) and astrocyte-like progenitors (AsLPs). In contrast to AsLPs, which are commonly observed in other brain regions, BGLPs have not been well studied. Here, we investigate differentiation abilities, gene expression profiles and differentiation control mechanisms of BGLPs at postnatal stages. BGLPs and AsLPs decrease in number as development progresses from postnatal day 0 (P0), and are almost absent by P10. By utilizing an electroporation-based method to BGLPs, we found that P6 BGLPs differentiate into BGs and IGL astrocytes, but not into WM astrocytes, consistent with a previous report. However, P0 BGLPs were observed to differentiate into not only BGs and IGL astrocytes, but also WM astrocytes and a small number of molecular layer inhibitory neurons. By conducting spatial transcriptomic analysis with over 5000 probes (Xenium), we successfully identified distinct clusters corresponding to BGLPs at P0 and P6, respectively, and genes preferentially expressed in P0 and P6 BGLPs. In addition, upstream regulatory analysis using Enrichr identified Foxm1 and Nfia as candidate regulators that affect stage-specific properties of BGLPs. in vivo knockdown and overexpression experiments further demonstrated that precise regulation of Foxm1 and Nfia expression is important for proper progeny production from postnatal BGLPs. This study gives insights into understanding molecular nature and differentiation ability control of BGLPs during postnatal cerebellar development.
The Alzheimer's disease protective P522R PLCG2 coding variant (rs72824905) is downstream of TREM2, but how it confers disease protection is poorly understood. Using a Plcg2-R522 knock-in mouse and Plcg2-P522 control on both wildtype and Alzheimer's disease-like AppNL-G-F amyloidosis mouse backgrounds, aged mice were assayed for amyloid load, microglial activity, and synaptic integrity. In the absence of Alzheimer's disease-like pathology, the R522 variant increased microglial coverage and was associated with reduced ramification complexity, fewer terminal points, and elevated lysosomal CD68 expression. On the AppNL-G-F background, total amyloid burden was unaffected, but expression of the R522 variant led to increased plaque compaction compared to the P522 common variant. The protective R522 variant was also associated with: enhanced microglial engagement with less compact amyloid plaques; reduced microglial localisation around highly compacted plaques; protection from amyloid-induced synapse loss; and decreased engulfment of synaptic material by microglia. Our data indicate a significant direct PLCγ2 role in controlling microglial-plaque interactions and synaptic protection downstream of amyloid deposition, prioritizing it as a therapeutic target, potentially as an adjunct to other approaches, such as those targeting amyloid.
