Biology subjects

Eroglu, C.

Publications and source records attributed to Eroglu, C..

At least 19 recordsLinked to original sources

bioRxiv2026

An astrocytic AMPAR-dependent parity signal preserves synaptic strength

Astrocytic processes closely associate with excitatory synapses and express AMPARs, positioning them to sense the same glutamate signals as neurons. Whether a mismatch between neuronal and astrocytic glutamate sensing affects synaptic physiology is unknown. Using AstroHTP, an extension of Drug Acutely Restricted by Tethering (DART) for cell-type-specific pharmacology, we found that acute astrocytic AMPAR inhibition spared neuronal AMPARs and basal transmission yet converted ongoing glutamatergic activity into a remarkably potent form of long-term depression (LTD) in mouse striatal projection neurons (SPNs). Unlike canonical presynaptic LTD, this form of LTD manifests postsynaptically, requires non-ionotropic NMDA receptor signaling, and arises when glutamate transmission occurs without a matching astrocytic signal. Astrocytic glutamate sensing through AMPARs, therefore, acts as a parity signal that verifies transmission and stabilizes active synapses.

neuroscience↗

bioRxiv2026

δ-catenin controls layer-specific transcriptional maturation of astrocytes via Zbtb20

Coordinated maturation of diverse neural cell types drives mammalian cortical circuit development. Disruption of this coordination is a hallmark of human neurodevelopmental disorders, yet mechanisms that synchronize transcriptional maturation across cell types remain poorly understood. Here, we identify {delta}-catenin (Ctnnd2), a component of adherens junctions, that links cell-cell interactions to transcriptional regulation. Using single-nucleus and spatial transcriptomics, we show that {delta}-catenin loss disrupts transcriptional maturation across neural cell types, particularly in astrocytes. {delta}-catenin loss impairs acquisition of layer-specific astrocyte identities and prolongs ocular dominance plasticity, indicating impaired circuit stabilization. Mechanistically, we identify the BTB/POZ transcription factor Zbtb20, which is enriched in glial cells, as a key regulator of this process. {delta}-catenin loss increases Zbtb20 expression, redistributes its genome-wide binding, and dysregulates its target genes. Together, these findings support a model in which {delta}-catenin regulates Zbtb20-dependent transcriptional programs to establish layer-specific astrocyte identities in coordination with developing cortical circuits. SUMMARYSejourne et al report that loss of the adherens junction protein {delta}-catenin prolongs ocular dominance plasticity and disrupts astrocyte and oligodendrocyte transcriptional identity. The underlying mechanism seems to rely on the glia-enriched transcription factor Zbtb20, which is upregulated and redistributed upon {delta}-catenin loss, resulting in altered expression of its target genes.

cell biology↗

bioRxiv2026

Reprogramming of neuronal genome function and phenotype by astrocytes

Heterotypic cell-cell interactions are critical to governing cellular physiology, disease progression, and responses to the environment and pharmacologic interventions. For example, neurons and astrocytes engage in intricate interactions that are essential for brain development and function1-3. However, the transformation of these extracellular signals into epigenomic regulation that governs cell function is poorly understood. Here, we report that weeks of co-culture between human induced pluripotent stem cell (hiPSC)-derived neurons and mouse cortical astrocytes extensively reprograms gene expression and the chromatin accessibility landscape in neurons, affecting thousands of genes and putative gene regulatory elements (REs), including many transcription factors (TFs). These genes are enriched for functions implicated in neuronal differentiation and maturation, and tend to be impacted in schizophrenia, and autosomal dominant Alzheimers disease. Through complementary CRISPR interference and activation screens, we recapitulated hundreds of astrocyte-induced transcriptional and chromatin remodeling events in mono-cultured neurons at both promoters and distal regulatory elements (REs) of TF genes. We discovered functional REs for [~]50 astrocyte-responsive TF genes, providing a map of gene regulatory network control. Astrocyte-responsive TF genes fall into groups that exert independent or counter-balancing transcriptional effects, highlighting the complex coordination of the neuronal response to astrocytes. Functional effects of specific TFs, including POU3F2 and TFAP2E, on neurite morphology and neuronal electrophysiology are consistent with transcriptional effects, demonstrating the capacity of direct epigenetic control to mimic heterotypic cellular signals. This work illuminates the regulation of neurodevelopment-and disease-relevant gene modules by neuron-astrocyte interactions, and provides a blueprint for applying modern functional genomics to uncover the links between cell microenvironment and epigenomic programming. HighlightsO_LINeuronal gene expression and chromatin accessibility landscape are profoundly remodeled by astrocytes over weeks of co-culture C_LIO_LIAstrocyte-responsive neuronal gene modules and neuron-responsive astrocytic gene modules are enriched for genes associated with schizophrenia and familial Alzheimers Disease C_LIO_LISingle-cell CRISPR interference and activation screens of astrocyte-responsive gene regulatory elements identified dozens of functional regulatory elements of TF genes in neurons C_LIO_LISingle-cell CRISPR interference and activation screens of >200 astrocyte-responsive TF genes uncovered discrete functional clusters that promote neuronal maturity or stemness C_LIO_LIAstrocyte-responsive TF genes reprogram neuronal electrophysiology and neurite morphology C_LI

genomics↗

bioRxiv2026

Phosphatidylserine exposure by developing astrocytes initiates microglia-mediated developmental cell death

Developmental cell death is classically attributed to apoptosis, yet in mammalian retina, large numbers of developing astrocytes die non-apoptotically during a defined developmental window. Astrocyte death is important for patterning a cellular template that guides angiogenesis, but the underlying mechanism remains unknown. Here we show that healthy developing astrocytes initiate their own elimination by recruiting microglia via regulated exposure of the membrane lipid phosphatidylserine. Experimentally increasing phosphatidylserine exposure in astrocytes, but not neurons, accelerates their removal by microglia without changing how many astrocytes ultimately survive. This acceleration causes profound vascular defects resembling pathological features of retinopathy of prematurity. Genetic disruption of MFGE8, a phosphatidylserine-binding protein, suppresses microglia-mediated astrocyte killing and prevents vascular pathology despite continued phosphatidylserine exposure. This mechanism extends beyond the retina, because phosphatidylserine also initiates astrocyte death in developing cerebral cortex. Together, these findings identify phosphatidylserine exposure as a developmental signal that times microglia-mediated astrocyte elimination, with essential consequences for neurovascular development.

neuroscience↗

bioRxiv2025

Neuroligin-2 is ubiquitinated by Nedd4l to control developmental astrocyte morphogenesis.

Central nervous system astrocytes have an intricate, highly branched morphology. Proper development of perisynaptic astrocyte processes is necessary for tripartite synapse formation and function. However, cellular pathways orchestrating this development are largely unknown. Neuroligins (NLs) 1-3 regulate astrocyte morphogenesis via transcellular adhesions with neuronal neurexins. Here, we found an astrocytic NL2-based mechanism governing morphogenesis. Through structure and function studies, we identified a WW-binding motif within the NL2 intracellular domain required for astrocyte morphogenesis. Using cell-specific in vivo proximity labeling (iBioID), we found that each NL displays distinct protein-protein interactions within astrocytes, distinct from the neuronal NL2 binding partners. From these data, we identified a role for WW domain-containing E3 ubiquitin ligase Nedd4l in astrocyte morphogenesis. Biochemical assays revealed Nedd4l ubiquitinates and stabilizes NL2, and this ubiquitination is required for astrocyte morphogenesis. This study shows that Neuroligins have non-overlapping roles in controlling astrocyte growth and uncovers a molecular mechanism of how NL2 mediates astrocyte morphogenesis. SUMMARYSakers et al report that astrocytic neuroligins (NLs) are functionally diverse proteins, with unique intracellular protein-protein interactions. They show that Nedd4l binds to NL2 and ubiquitinates its intracellular domain, leading to changes in NL2 stability. In vivo, Nedd4l and NL2 ubiquitination are critical for astrocyte morphogenesis.

cell biology↗

bioRxiv2025

Elucidating an anterior cingulate circuit for self-initiated actions and rescue of Parkinsonian akinesia

Dopamine (DA) depletion is known to result in Parkinsonian symptoms such as the inability to initiate movements (akinesia). While Parkinsonian akinesia is traditionally associated with reduced DA signaling in the striatum, the contribution of cortical regions that also receive DA projections and project to the striatum remains unclear. Here, we identify a previously unexplored cortical circuit involving D1-like dopamine receptor-expressing neurons in the anterior cingulate cortex (ACC) that is critical for initiating goal-directed movements. We find that a selective activation of ACC-D1+ neurons can flexibly drive targeted movement and locomotion even in akinetic mice after dopamine depletion or receptor antagonism. These findings uncover a cortical mechanism for movement initiation and offer promising new therapeutic targets for treating Parkinsonian akinesia.

neuroscience↗

bioRxiv2024

Mitochondrial fission controls astrocyte morphogenesis and organization in the cortex

Dysfunctional mitochondrial dynamics are a hallmark of devastating neurodevelopmental disorders such as childhood refractory epilepsy. However, the role of glial mitochondria in proper brain development is not well understood. We show that astrocyte mitochondria undergo extensive fission while populating astrocyte distal branches during postnatal cortical development. Loss of mitochondrial fission regulator, Dynamin-related protein 1 (Drp1), decreases mitochondrial localization to distal astrocyte processes, and this mitochondrial mislocalization reduces astrocyte morphological complexity. Functionally, astrocyte-specific conditional deletion of Drp1 induces astrocyte reactivity and disrupts astrocyte organization in the cortex. These morphological and organizational deficits are accompanied by loss of perisynaptic astrocyte process (PAP) proteins such as gap junction protein Connexin 43. These findings uncover a crucial role for mitochondrial fission in coordinating astrocytic morphogenesis and organization, revealing the regulation of astrocytic mitochondria dynamics as a critical step in neurodevelopment. SummaryDuring cortical astrocyte morphogenesis, mitochondria fragment and decrease in size to populate distal astrocyte processes. Drp1-mediated mitochondrial fission is necessary for peripheral astrocyte process formation. Astrocyte-specific Drp1 loss induces astrocyte reactivity, disrupts cortical astrocyte organization, and dysregulates PAP proteins including gap-junction protein Connexin 43 abundance.

cell biology↗

bioRxiv2024

Astrocytic thrombospondins 1 and 2 are required for cortical synapse development controlling instrumental performance

During development, controlled synaptogenesis is required to form functioning neural circuits that underlie cognition and behavior. Astrocytes, a major glial-cell type in the central nervous system (CNS), promote synapse formation by secreting synaptogenic proteins. Thrombospondins 1 and 2 (TSP1/2), which act through their neuronal receptor 2{delta}-1, are required for proper intracortical excitatory synaptogenesis. In the adult brain, the loss of 2{delta}-1 impairs training-induced excitatory synaptogenesis in the anterior cingulate cortex (ACC), and this impairment leads to increased effort-exertion during high-effort tasks. Here, we tested whether TSP1 and TSP2 are required for controlling effort during operant conditioning by using a lever press for food reward training in mice. Surprisingly, we found that constitutive loss of TSP1/2 significantly reduced lever pressing performance when the effort required for a food reward was increased, a phenotype opposite of 2{delta}-1 loss. Loss of TSP1/2 reduced excitatory synapse number significantly in adult brains. However, in the ACC of TSP1/2 knockout mice, there was still training-induced excitatory synaptogenesis, likely through the upregulation of TSP4, a TSP isoform that is also synaptogenic. Unexpectedly, we also found a significant increase in inhibitory synapse number and function in the ACC of TSP1/2 knockout mice, which was eliminated after training. Finally, we found that astrocyte-specific ablation of TSP1/2 in developing but not adult astrocytes is sufficient to reduce performance during high-effort tasks. Taken together, our study highlights the importance of developmental astrocyte-derived synaptogenic cues TSP1 and 2 in establishing excitatory and inhibitory circuits that control effort during operant conditioning in adults.

neuroscience↗

bioRxiv2023

SynBot: An open-source image analysis software for automated quantification of synapses

The formation of precise numbers of neuronal connections, known as synapses, is crucial for brain function. Therefore, synaptogenesis mechanisms have been one of the main focuses of neuroscience. Immunohistochemistry is a common tool for visualizing synapses. Thus, quantifying the numbers of synapses from light microscopy images enables screening the impacts of experimental manipulations on synapse development. Despite its utility, this approach is paired with low throughput analysis methods that are challenging to learn and results are variable between experimenters, especially when analyzing noisy images of brain tissue. We developed an open-source ImageJ-based software, SynBot, to address these technical bottlenecks by automating the analysis. SynBot incorporates the advanced algorithms ilastik and SynQuant for accurate thresholding for synaptic puncta identification, and the code can easily be modified by users. The use of this software will allow for rapid and reproducible screening of synaptic phenotypes in healthy and diseased nervous systems. MotivationLight microscopy imaging of pre- and post-synaptic proteins from neurons in tissue or in vitro allows for the effective identification of synaptic structures. Previous methods for quantitative analysis of these images were time-consuming, required extensive user training, and the source code could not be easily modified. Here, we describe SynBot, a new open-source tool that automates the synapse quantification process, decreases the requirement for user training, and allows for easy modifications to the code.

neuroscience↗

bioRxiv2023

Astrocytic LRRK2 Controls Synaptic Connectivity through ERM Phosphorylation

Astrocytes are highly complex cells that mediate critical roles in synapse formation and maintenance by establishing thousands of direct contacts with synapses through their perisynaptic processes. Here, we found that the most common Parkinsonism gene mutation, LRRK2 G2019S, enhances the phosphorylation of the ERM proteins (Ezrin, Radixin, and Moesin), components of the perisynaptic astrocyte processes in a subset of cortical astrocytes. The ERM hyperphosphorylation was accompanied by decreased astrocyte morphological complexity and reduced excitatory synapse density and function. Dampening ERM phosphorylation levels in LRRK2 G2019S mouse astrocytes restored both their morphology and the excitatory synapse density in the anterior cingulate cortex. To determine how LRRK2 mutation impacts Ezrin interactome, we used an in vivo BioID proteomic approach, and we found that astrocytic Ezrin interacts with Atg7, a master regulator of autophagy. The Ezrin/Atg7 interaction is inhibited by Ezrin phosphorylation, thus diminished in LRRK2 G2019S astrocytes. Importantly, the Atg7 function is required to maintain proper astrocyte morphology. Our data provide a molecular pathway through which the LRRK2 G2019S mutation alters astrocyte morphology and synaptic density in a brain-region-specific manner.

neuroscience↗

bioRxiv2023

Astrocyte-Secreted Neurocan Controls Inhibitory Synapse Formation and Function

Astrocytes strongly promote the formation and maturation of synapses by secreted proteins. To date, several astrocyte-secreted synaptogenic proteins controlling different stages of excitatory synapse development have been identified. However, the identities of astrocytic signals that induce inhibitory synapse formation remain elusive. Here, through a combination of in vitro and in vivo experiments, we identified Neurocan as an astrocyte-secreted inhibitory synaptogenic protein. Neurocan is a chondroitin sulfate proteoglycan that is best known as a protein localized to the perineuronal nets. However, Neurocan is cleaved into two after secretion from astrocytes. We found that the resulting N- and C-terminal fragments have distinct localizations in the extracellular matrix. While the N-terminal fragment remains associated with perineuronal nets, the Neurocan C-terminal fragment localizes to synapses and specifically controls cortical inhibitory synapse formation and function. Neurocan knockout mice lacking the whole protein or only its C-terminal synaptogenic region have reduced inhibitory synapse numbers and function. Through super-resolution microscopy and in vivo proximity labeling by secreted TurboID, we discovered that the synaptogenic domain of Neurocan localizes to somatostatin-positive inhibitory synapses and strongly regulates their formation. Together, our results unveil a mechanism through which astrocytes control circuit-specific inhibitory synapse development in the mammalian brain.

neuroscience↗

bioRxiv2023

GEARBOCS: An Adeno Associated Virus Tool for In Vivo Gene Editing in Astrocytes

CRISPR/Cas9-based genome engineering enables rapid and precise gene manipulations in the CNS. Here, we developed a non-invasive astrocyte-specific method utilizing a single AAV vector, which we named GEARBOCS (Gene Editing in AstRocytes Based On CRISPR/Cas9 System). We verified GEARBOCS specificity to mouse cortical astrocytes and demonstrated its utility for three types of gene manipulations: knockout (KO); tagging (TagIn); and reporter knock-in (GeneTrap) strategies. Next, we deployed GEARBOCS in two test cases. First, we determined that astrocytes are a necessary source of the synaptogenic factor Sparcl1 for thalamocortical synapse maintenance in the mouse primary visual cortex. Second, we determined that cortical astrocytes express the synaptic vesicle associated Vamp2 protein and found that it is required for maintaining excitatory and inhibitory synapse numbers in the visual cortex. These results show that the GEARBOCS strategy provides a fast and efficient means to study astrocyte biology in vivo. MotivationAstrocytes are indispensable for brain development, function, and health. However, molecular tools to study astrocyte biology and function in vivo have been largely limited to genetically modified mice. Here, we developed a CRISPR/Cas9-based gene editing strategy within a single AAV vector that enables efficient genome manipulations in astrocytes. We designed and optimized this easy-to-use viral tool to understand gene expression, protein localization and function in astrocytes in vivo.

neuroscience↗

bioRxiv2023

Functional gene delivery to and across brain vasculature of systemic AAVs with endothelial-specific tropism in rodents and broad tropism in primates

Delivering genes to and across the brain vasculature efficiently and specifically across species remains a critical challenge for addressing neurological diseases. We have evolved adeno-associated virus (AAV9) capsids into vectors that transduce brain endothelial cells specifically and efficiently following systemic administration in wild-type mice with diverse genetic backgrounds and rats. These AAVs also exhibit superior transduction of the CNS across non-human primates (marmosets and rhesus macaques), and ex vivo human brain slices although the endothelial tropism is not conserved across species. The capsid modifications translate from AAV9 to other serotypes such as AAV1 and AAV-DJ, enabling serotype switching for sequential AAV administration in mice. We demonstrate that the endothelial specific mouse capsids can be used to genetically engineer the blood-brain barrier by transforming the mouse brain vasculature into a functional biofactory. Vasculature-secreted Hevin (a synaptogenic protein) rescued synaptic deficits in a mouse model.

bioengineering↗

bioRxiv2022

Autism-associated mutation in Hevin/Sparcl1 induces endoplasmic reticulum stress through structural instability

Hevin is a secreted extracellular matrix protein that is encoded by SPARCL1 gene. Recent studies show that Hevin plays an important role in regulating synaptogenesis and synaptic plasticity. Mutations in SPARCL1 gene increase the risk of autism spectrum disorder (ASD). However, the molecular basis of how mutations in SPARCL1 increase the risk of ASD has not been fully understood. In this study, we show that one of SPARCL1 mutations associated with ASD impairs normal Hevin secretion. We identified Hevin mutants lacking the EF-hand motif through analyzing ASD-related mice with vulnerable spliceosome functions. Hevin deletion mutants accumulate in the ER, leading to the activation of unfolded protein responses. We also found that a single amino acid substitution of Trp647 with Arg in the EF-hand motif associated with a familial case of ASD causes a similar phenotype with the EF-hand deletion mutant. Importantly, molecular dynamics (MD) simulation revealed that this single amino acid substitution triggers exposure of hydrophobic amino acid to the surface, increasing the binding of Hevin with a molecular chaperon, BIP. Taken together, these data suggest that the integrity of EF-hand motif in Hevin is crucial for proper folding and ASD-related mutation impairs an export of Hevin from the endoplasmic reticulum (ER). Our data provide a novel mechanism linking a point mutation in SPARCL1 gene to the molecular and cellular characteristics involved in ASD.

molecular biology↗

bioRxiv2022

Sparcl1/Hevin drives inflammatory and neuropathic pain through astrocyte and NMDA receptor signaling

Hevin/Sparcl1 is an astrocyte-secreted protein and regulates synapse formation in the brain. Here we show that astrocytic hevin signaling plays a critical role in maintaining chronic pain. Compared to wild-type mice, hevin-null mice exhibited normal mechanical and heat sensitivity but reduced inflammatory pain. Interestingly, hevin is required for the maintenance of nerve injury-induced neuropathic pain (mechanical allodynia), and hevin-null mice have faster recovery than wild-type mice from neuropathic pain after nerve injury. Intrathecal injection of wild-type hevin but not a hevin mutant that is no longer synaptogenic was sufficient to induce persistent mechanical allodynia in naive mice and further enhanced neuropathic pain in animals with nerve injury. In hevin-null mice with nerve injury, AAV-mediated re-expression of hevin, but not mutant hevin, in GFAP-expressing spinal cord astrocytes could reinstate neuropathic pain. Mechanistically, hevin is crucial for spinal cord NMDA receptor (NMDAR) signaling, as NMDA-induced mechanical allodynia and inward currents in spinal cord lamina II neurons is reduced in hevin-null mice. Hevin potentiated NMDA currents mediated by the GluN2B-containing NMDARs. Furthermore, intrathecal injection of a neutralizing antibody against hevin alleviated acute inflammatory pain and persistent neuropathic pain. Secreted hevin was detected in mouse cerebrospinal fluid (CSF) and nerve injury significantly increased CSF hevin abundance. Finally, neurosurgery caused rapid (< 10 hours) and substantial increases (~20 fold) in HEVIN levels in human CSF. Collectively, our findings support a critical role of hevin and astrocytes in the maintenance of chronic pain. Neutralizing of secreted hevin with monoclonal antibody may provide a new therapeutic strategy for treating chronic pain and NMDAR-medicated neurodegeneration.

neuroscience↗

bioRxiv2021

Excitatory synaptogenesis in the anterior cingulate cortex is required for effort/reward evaluation

Synaptogenesis is essential for circuit development; however, it is unknown whether it is critical for the establishment and performance of goal-directed voluntary behaviors. Here, we show that operant-conditioning via lever-press for food reward-training in mice induces excitatory synapse formation onto a subset of Anterior Cingulate Cortex neurons projecting to the dorsomedial striatum (ACC->DMS). Training-induced synaptogenesis is controlled by the Gabapentin/Thrombospondin receptor 2{delta}-1, which is an essential neuronal protein for proper intracortical excitatory synaptogenesis. Using germline and conditional knockout mice, we found that deletion of 2{delta}-1 in the adult ACC->DMS circuit diminishes training-induced excitatory synaptogenesis. Surprisingly, this manipulation did not impact learning but instead resulted in a profound increase in effort exertion without affecting sensitivity to reward value or changing contingencies. Bidirectional optogenetic manipulation of ACC->DMS neurons rescued or phenocopied the behaviors of the 2{delta}-1 cKO mice highlighting the importance of synaptogenesis within this cortico-striatal circuit in regulating effort exertion.

neuroscience↗

bioRxiv2020

Prenatal Environmental Stressors Impair Postnatal Microglia Function and Adult Behavior in Males

Gestational exposure to environmental toxins and socioeconomic stressors are epidemiologically linked to neurodevelopmental disorders with strong male-bias, such as autism. We modeled these prenatal risk factors in mice, by co-exposing pregnant dams to an environmental pollutant and limited-resource stress, which robustly activated the maternal immune system. Only male offspring displayed long-lasting behavioral abnormalities and alterations in the activity of brain networks encoding social interactions. Cellularly, prenatal stressors diminished microglial function within the anterior cingulate cortex, a central node of the social coding network, in males during early postnatal development. Genetic ablation of microglia during the same critical period mimicked the impact of prenatal stressors on a male-specific behavior, indicating that environmental stressors alter neural circuit formation in males via impairing microglia function during development.

neuroscience↗

bioRxiv2019

Thrombospondin-1 Promotes Circuit-Specific Synapse Formation via β1-Integrin

Glial cells regulate synaptic connectivity during development, but whether they selectively instruct the formation of specific synaptic circuits is not known. Here we show that the major perisynaptic glia of the retina, the Muller glia (MG), control the proper establishment of the direction-selective (DS) circuit by a synaptogenic protein, Thrombospondin 1 (TSP1). We found that TSP1 promotes excitatory synapse formation specifically in on-off Direction-Selective retinal Ganglion Cells (ooDSGCs). Lack of TSP1 leads to reduced synapse formation within the inner plexiform sublayers containing DS-circuit, resulting in deficits of ooDSGC function. Even though pan-TSP receptor, 2{delta}-1, interaction is required for TSP1-induced synapse formation, the ooDSGC-subtype specificity of TSP1 is conferred by a second neuronal TSP1 receptor, {beta}1-Integrin. Furthermore, conditional deletion of {beta}1-Integrin in ooDSGCs results in diminished excitatory synapse formation without disturbing laminar organization showing that MG-secreted TSP1 controls circuit-specific synapse formation via {beta}1-Integrin.

neuroscience↗