Biology subjects

Condello, C.

Publications and source records attributed to Condello, C..

16 recordsLinked to original sources

bioRxiv2026

DAP12-deficient microglia adopt a TREM2-independent antigen-presenting state with a glial-to-neuronal cascade in Nasu-Hakola disease

Nasu-Hakola disease (NHD), a dementia with about 200 cases worldwide, is caused by loss-of-function mutation of TYROBP, encoding DAP12, or its receptor TREM2. TREM2-DAP12 is the switch that converts microglia from a surveillant to a reactive state; what DAP12-deficient microglia become and to what extent they reshape their microenvironment is unknown. We profiled prefrontal cortex and hippocampus from an NHD donor and control by single-nucleus RNA sequencing and mapped the glial changes in situ by spatial transcriptomics. NHD microglia adopted a CIITA-driven, MHC class II-high antigen-presenting state with complement, iron and glycolytic programs and Fc receptors but not the TREM2-dependent lipid program. Astrocytes became pan-reactive and lost metallothionein expression, oligodendrocytes lost mature cells and cholesterol synthesis, and excitatory neurons lost presynaptic and activity programs, consistently between regions and across a published cohort. DAP12 deficiency left microglia in an antigen-presenting state short of the TREM2-dependent arm, accompanied by a glial-to-neuronal cascade.

neuroscience↗

bioRxiv2026

Spatially resolved transcriptome-metabolome integration reveals region-specific glial lipid dysregulation associated with Alzheimer's pathology

Glial cells maintain the brains lipid and energy balance, and their breakdown is increasingly recognized as a causal contributor to Alzheimers disease (AD). While this concept is established, no approach has directly shown how glial homeostatic failure manifests across brain regions and microenvironments or how it links local pathology, such as plaques, to global metabolic imbalance. To address this gap, we developed iMIST, an integrated platform that combines MALDI-based metabolite imaging, histology, and spatial transcriptomics within a single tissue section to align molecular and anatomical information. Using a mouse model of late-onset AD that recapitulates both amyloid deposition and metabolic vulnerability, iMIST revealed that glial lipid dysregulation is widespread but spatially specialized. In gray matter, plaque-associated microglia were associated with upregulated glycerophospholipid-remodeling in cortico-thalamic areas indicating metabolic stress around local pathology. In contrast, white matter tracts rich in lipid-producing oligodendrocytes show plaque-independent deficits in galactosylceramide metabolism reflecting their high myelin demand. Both processes intensify with age, transforming adaptive glial responses into persistent metabolic dysfunction. Together, these findings demonstrate the spatial interplay between global glial metabolic imbalance and local microenvironmental stressors associated with AD pathology. By integrating transcriptomic and metabolomic information in situ, iMIST provides a framework for uncovering how regional glial vulnerability shapes the pathogenesis of neurodegenerative diseases.

neuroscience↗

bioRxiv2025

Tri-AD: Hippocampal cell-type-specific responses to age, sex and APOE genotype

Alzheimers disease (AD) risk is strongly shaped by age, sex, and the apolipoprotein E {varepsilon}4 (APOE4) allele--the strongest genetic risk factor for late-onset AD. While each factor has been studied independently, their combined impact on cellular and molecular processes remains unclear. Here, we used single-nucleus RNA sequencing (snRNA-seq) to profile hippocampal cell states in a sex-balanced cohort of human APOE4/4 and APOE3/3 knock-in mice across 6, 12, and 18 months of age. We identify sex as the major driver of variation in cell-type abundance and find that oligodendrocytes exhibit pronounced male-biased transcriptional sensitivity to APOE4. Differential expression and cell-cell communication analyses further reveal sex-divergent temporal trajectories in inhibitory neurons, with females showing early APOE4-associated suppression of synaptic pathways and males displaying a delayed but convergent decline. Together, these findings clarify how age, sex, and APOE genotype jointly regulate cell-type-specific gene expression and intercellular communication in the aging hippocampus, providing an innovative and publicly accessible database for aging and AD research and related precision medicine.

bioinformatics↗

bioRxiv2025

β-Amyloid Induces Microglial Expression of GPC4 and APOE Leading to Increased Neuronal Tau Pathology and Toxicity

To elucidate the impact of A{beta} pathology on microglia in Alzheimers disease pathogenesis, we profiled the microglia surfaceome following treatment with A{beta} fibrils. Our findings reveal that A{beta}-associated human microglia upregulate Glypican 4 (GPC4), a GPI-anchored heparan sulfate proteoglycan (HSPG). In a Drosophila amyloidosis model, glial GPC4 expression exacerbates motor deficits and reduces lifespan, indicating that glial GPC4 contributes to a toxic cellular program during neurodegeneration. In cell culture, GPC4 enhances microglia phagocytosis of tau aggregates, and shed GPC4 can act in trans to facilitate tau aggregate uptake and seeding in neurons. Additionally, our data demonstrate that GPC4-mediated effects are amplified in the presence of APOE. These studies offer a mechanistic framework linking A{beta} and tau pathology through microglial HSPGs and APOE.

neuroscience↗

bioRxiv2024

Intracortical injection of immune checkpoint inhibitor promotes monocyte/macrophage infiltration and restores microglial function and neuronal activity in an AD mouse model

Alzheimer's disease (AD) involves complex neuroimmune interactions. However, the role of immune checkpoint pathways in regulating the glial and neuronal functions of the AD brain remains unclear. This study aims to investigate how the brain-specific modulation of the PD-1/PD-L1 axis affects glial and neuronal function in an AD mouse model, which is characterized by the significant upregulation of microglial PD-1 and astrocytic PD-L1. A single intracortical administration of anti-PD-L1 antibody reshaped the glial microenvironment, which was accompanied by the restoration of impaired microglial process convergence. Astrocyte-specific Pd-l1 knockdown using the pSico system validated the essential role of astrocytic PD-L1 in enhancing microglial responses. Notably, the blockade of the PD-1/PD-L1 signaling pathway increased the microglial P2RY12 expression, a key marker of microglial homeostasis, which likely contributed to the restoration of neuronal hyperactivity. Collectively, these findings confirmed the potential of targeting the astrocyte-microglia PD-1/PD-L1 axis to mitigate AD pathology.

neuroscience↗

bioRxiv2024

Methods for high throughput discovery of fluoroprobes that recognize tau fibril polymorphs

Aggregation of microtubule-associated protein tau (MAPT/tau) into conformationally distinct fibrils underpins neurodegenerative tauopathies. Fluorescent probes (fluoroprobes), such as thioflavin T (ThT), have been essential tools for studying tau aggregation; however, most of them do not discriminate between amyloid fibril conformations (polymorphs). This gap is due, in part, to a lack of high-throughput methods for screening large, diverse chemical collections. Here, we leverage advances in protein adaptive differential scanning fluorimetry (paDSF) to screen the Aurora collection of 300+ fluorescent dyes against multiple synthetic tau fibril polymorphs. This screen, coupled with orthogonal secondary assays, revealed pan-fibril binding chemotypes, as well as fluoroprobes selective for subsets of fibrils. One fluoroprobe recognized tau pathology in ex vivo brain slices from Alzheimers disease patients. We propose that these scaffolds represent entry points for development of selective fibril ligands and, more broadly, that high throughput, fluorescence-based dye screening is a platform for their discovery.

biochemistry↗

bioRxiv2024

Integrative Transcriptomics Reveals Layer 1 Astrocytes Altered in Schizophrenia

Schizophrenia is one of the most prevalent psychiatric disorders with unclear pathophysiology despite a century-long history of intense research. Schizophrenia affects multiple networks across different brain regions. The anterior cingulate cortex (ACC) is the region that connects the limbic system to cognitive areas such as the prefrontal cortex and represents a pivotal region for the etiology of schizophrenia; however, the molecular pathology, considering its cellular and anatomical complexity, is not well understood. Here, we performed an integrative analysis of spatial and single-nucleus transcriptomics of the postmortem ACC of people with schizophrenia, together with a thorough histological analysis. The data revealed major transcriptomics signatures altered in schizophrenia, pointing at the dysregulation of glial cells, primarily in astrocytes. We further discovered a decrease in the cellular density and abundance of processes of interlaminar astrocytes, a subpopulation of astrocytes specific to primates that localize in the layer 1 and influence the superficial cortical microenvironment across layer 1 and layers 2/3 of the cortex. Our study suggests that aberrant changes in interlaminar astrocytes could explain the cell-to-cell circuit alterations found in schizophrenia and represent novel therapeutic targets to ameliorate schizophrenia-associated dysfunction.

neuroscience↗

bioRxiv2024

Cryo-EM Structures Reveal Tau Filaments from Down Syndrome Adopt Alzheimer's Disease Fold

Down syndrome (DS) is a common genetic condition caused by trisomy of chromosome 21. Among their complex clinical features, including musculoskeletal, neurological, and cardiovascular disabilities, individuals with DS have an increased risk of developing progressive dementia and early-onset Alzheimers disease (AD). This dementia is attributed to the increased gene dosage of the amyloid-{beta} (A{beta}) precursor protein gene, the formation of self-propagating A{beta} and tau prion conformers, and the deposition of neurotoxic A{beta} plaques and tau neurofibrillary tangles. Tau amyloid fibrils have previously been established to adopt many distinct conformations across different neurodegenerative conditions. Here, we report the characterization of brain samples from four DS cases spanning 36 to 63 years of age by spectral confocal imaging with conformation-specific dyes and cryo-electron microscopy (cryo-EM) to determine structures of isolated tau fibrils. High-resolution structures revealed paired helical filament (PHF) and straight filament (SF) conformations of tau that were identical to those determined from AD cases. The PHFs and SFs are made of two C-shaped protofilaments, each containing a cross-{beta}/{beta}-helix motif. Similar to filaments from AD cases, most filaments from the DS cases adopted the PHF form, while a minority (approximately 20%) formed SFs. Samples from the youngest individual with no documented dementia had sparse tau deposits. To isolate tau for cryo-EM from this challenging sample we used a novel affinity-grid method involving a graphene oxide surface derivatized with anti-tau antibodies. This method improved isolation and revealed that primarily tau PHFs and a minor population of chronic traumatic encephalopathy type II-like filaments were present in this youngest case. These findings expand the similarities between AD and DS to the molecular level, providing insight into their related pathologies and the potential for targeting common tau filament folds by small-molecule therapeutics and diagnostics.

neuroscience↗

bioRxiv2023

De novo Design of Peptides that Bind Specific Conformers of α-Synuclein

Insoluble amyloids rich in cross-{beta} fibrils are observed in a number of neurodegenerative diseases. Depending on the clinicopathology, the amyloids can adopt distinct supramolecular assemblies, termed conformational strains. However, rapid methods to study amyloid in a conformationally specific manner are lacking. We introduce a novel computational method for de novo design of peptides that tile the surface of -synuclein fibrils in a conformationally specific manner. Our method begins by identifying surfaces that are unique to the conformational strain of interest, which becomes a "target backbone" for the design of a peptide binder. Next, we interrogate structures in the PDB database with high geometric complementarity to the target. Then, we identify secondary structural motifs that interact with this target backbone in a favorable, highly occurring geometry. This method produces monomeric helical motifs with a favorable geometry for interaction with the strands of the underlying amyloid. Each motif is then symmetrically replicated to form a monolayer that tiles the amyloid surface. Finally, amino acid sequences of the peptide binders are computed to provide a sequence with high geometric and physicochemical complementarity to the target amyloid. This method was applied to a conformational strain of -synuclein fibrils, resulting in a peptide with high specificity for the target relative to other amyloids formed by -synuclein, tau, or A{beta}40. This designed peptide also markedly slowed the formation of -synuclein amyloids. Overall, this method offers a new tool for examining conformational strains of amyloid proteins.

biophysics↗

bioRxiv2023

CRISPR screens in iPSC-derived neurons reveal principles of tau proteostasis

Aggregation of the protein tau is a hallmark of Alzheimers disease and other tauopathies. Specific neuronal subtypes are selectively vulnerable to tau aggregation, but the underlying mechanisms are unknown. To systematically uncover the cellular factors controlling the accumulation of tau aggregates in human neurons, we conducted a genome-wide CRISPRi-based modifier screen in iPSC-derived neurons. The screen uncovered expected pathways, including autophagy, but also unexpected pathways, including UFMylation and GPI anchor synthesis, that control tau oligomer levels. We discover that the E3 ubiquitin ligase CUL5SOCS4 is a potent modifier of tau levels in human neurons, ubiquitinates tau, and is correlated with resilience to tauopathies in human disease. Disruption of mitochondrial function promotes proteasomal misprocessing of tau, which generates tau proteolytic fragments like those in disease and changes tau aggregation in vitro. These results reveal new principles of tau proteostasis in human neurons and pinpoint potential therapeutic targets for tauopathies.

cell biology↗

bioRxiv2023

Total Chemical Synthesis of Glycosylated TREM2 Ectodomain

Mutations in a microglia-associated gene TREM2 increase the risk of Alzheimers disease. Currently, structural and functional studies of TREM2 mainly rely on recombinant TREM2 proteins expressed from mammalian cells. However, using this method, it is difficult to achieve site-specific labeling. Here we present the total chemical synthesis of the 116 amino-acid TREM2 ectodomain. Rigorous structural analysis ensured correct structural fold after refolding. Treating microglial cells with refolded synthetic TREM2 enhanced microglial phagocytosis, proliferation, and survival. We also prepared TREM2 constructs with defined glycosylation patterns and found that glycosylation at N79 is critical to the thermal stability of TREM2. This method will provide access to TREM2 constructs with site-specific labeling, such as fluorescent labeling, reactive chemical handles, and enrichment handles, to further advance our understanding of TREM2 in Alzheimers disease.

biochemistry↗

bioRxiv2023

EMBER multi-dimensional spectral microscopy enables quantitative determination of disease- and cell-specific amyloid strains

In neurodegenerative diseases proteins fold into amyloid structures with distinct conformations (strains) that are characteristic of different diseases. However, there is a need to rapidly identify amyloid conformations in situ. Here we use machine learning on the full information available in fluorescent excitation/emission spectra of amyloid binding dyes to identify six distinct different conformational strains in vitro, as well as A{beta} deposits in different transgenic mouse models. Our EMBER (excitation multiplexed bright emission recording) imaging method rapidly identifies conformational differences in A{beta} and tau deposits from Down syndrome, sporadic and familial Alzheimers disease human brain slices. EMBER has in situ identified distinct conformational strains of tau inclusions in astrocytes, oligodendrocytes, and neurons from Picks disease. In future studies, EMBER should enable high-throughput measurements of the fidelity of strain transmission in cellular and animal neurodegenerative diseases models, time course of amyloid strain propagation, and identification of pathogenic versus benign strains. SignificanceIn neurodegenerative diseases proteins fold into amyloid structures with distinct conformations (strains) that are characteristic of different diseases. There is a need to rapidly identify these amyloid conformations in situ. Here we use machine learning on the full information available in fluorescent excitation/emission spectra of amyloid binding dyes to identify six distinct different conformational strains in vitro, as well as A{beta} deposits in different transgenic mouse models. Our imaging method rapidly identifies conformational differences in A{beta} and tau deposits from Down syndrome, sporadic and familial Alzheimers disease human brain slices. We also identified distinct conformational strains of tau inclusions in astrocytes, oligodendrocytes, and neurons from Picks disease. These findings will facilitate the identification of pathogenic protein aggregates to guide research and treatment of protein misfolding diseases.

neuroscience↗

bioRxiv2021

Emergence of distinct and heterogeneous strains of amyloid beta as Alzheimer s disease progresses in Down syndrome

0.Amyloid beta (A{beta}) is thought to play a critical role in the pathogenesis of Alzheimers disease (AD). Prion-like A{beta} polymorphs, or "strains", can have varying pathogenicity and may underlie the phenotypic heterogeneity of the disease. In order to develop effective AD therapies, it is critical to identify the strains of A{beta} that might arise prior to the onset of clinical symptoms and understand how they may change with progressing disease. Down syndrome (DS), as the most common genetic cause of AD, presents promising opportunities to compare such features between early and advanced AD. In this work, we evaluate the neuropathology and A{beta} strain profile in the post-mortem brain tissues of 210 DS, AD, and control individuals. We assayed the levels of various A{beta} and tau species and used conformation-sensitive fluorescent probes to detect differences in A{beta} strains among individuals and populations. We found that these cohorts have some common but also some distinct strains from one another, with the most heterogeneous populations of A{beta} emerging in subjects with high levels of AD pathology. The emergence of distinct strains in DS at these later stages of disease suggests that the confluence of aging, pathology, and other DS-linked factors may favor conditions that generate strains that are unique from sAD.

pathology↗

bioRxiv2021

A type I interferon response defines a conserved microglial state required for effective phagocytosis

Microglia are brain resident phagocytes that can engulf synaptic components and extracellular matrix as well as whole neurons. However, whether there are unique molecular mechanisms that regulate these distinct phagocytic states is unknown. Here we define a molecularly distinct microglial subset whose function is to engulf neurons in the developing brain. We transcriptomically identified a cluster of Type I interferon (IFN-I) responsive microglia that expanded 20-fold in the postnatal day 5 somatosensory cortex after partial whisker deprivation, a stressor that accelerates neural circuit remodeling. In situ, IFN-I responsive microglia were highly phagocytic and actively engulfed whole neurons. Conditional deletion of IFN-I signaling (Ifnar1fl/fl) in microglia but not neurons resulted in dysmorphic microglia with stalled phagocytosis and an accumulation of neurons with double strand DNA breaks, a marker of cell stress. Conversely, exogenous IFN-I was sufficient to drive neuronal engulfment by microglia and restrict the accumulation of damaged neurons. IFN-I deficient mice had excess excitatory neurons in the developing somatosensory cortex as well as tactile hypersensitivity to whisker stimulation. These data define a molecular mechanism through which microglia engulf neurons during a critical window of brain development. More broadly, they reveal key homeostatic roles of a canonical antiviral signaling pathway in brain development.

neuroscience↗

bioRxiv2021

Sex-specific life extension in tauopathy mice by CSF1R inhibition causing selective microglial depletion and suppressed pathogenesis

Microglia are central to pathogenesis in many neurological conditions. Drugs targeting colony- stimulating factor-1 receptor (CSF1R) to block microglial proliferation in preclinical disease models have shown mixed outcomes, thus the therapeutic potential of this approach remains unclear. Here, CSF1R inhibitors were evaluated in tauopathy mice using multiple dosing schemes, drug analogs, and longitudinal measurements in the brain and plasma. A sex- independent reduction in pathogenic tau was seen in several models and non-microglial gene expression patterns reverted toward a normal wild type signature. Surprisingly, despite greater drug exposure in male mice, functional rescue and extended survival was only observed in female mice. A dose-dependent upregulation of immediate early genes and neurotransmitter dysregulation were observed in the brains of male mice only, indicating that excitotoxicity may have precluded functional benefits. Drug-resilient microglia in male mice exhibited morphological and gene expression patterns consistent with increased neuroinflammatory signaling, suggesting a mechanistic basis for sex-specific excitotoxicity. These data argue that complete microglial ablation is neither required nor desirable for neuroprotection and that therapeutics targeting microglia must consider sex-dependent effects on functional outcomes.

neuroscience↗

bioRxiv2021

Microglial NF-κB drives tau spreading and toxicity in a mouse model of tauopathy

Activation of microglia, the brains innate immune cells, is a prominent pathological feature in tauopathies, including Alzheimers disease. How microglia activation contributes to tau toxicity remains largely unknown. Here we show that nuclear factor kappa-light-chain-enhancer of activated B cells (NF-{kappa}B) signaling, activated by tau, drives microglial-mediated tau propagation and toxicity. Constitutive activation of microglial NF-{kappa}B exacerbated, while inactivation diminished, tau seeding and spreading in PS19 mice, consistent with the observation that NF-{kappa}B activation accelerates processing of internalized tau fibrils in primary microglia. Remarkably, inhibition of microglial NF-{kappa}B specifically also rescued tau-mediated learning and memory deficits, and restored overall transcriptomic changes while increasing tau inclusions. On a single cell level, we discovered that tau-associated disease states in microglia were diminished by NF-{kappa}B inactivation and further transformed by constitutive NF-{kappa}B activation. Our study establishes a central role for microglial NF-{kappa}B signaling in mediating tau toxicity in tauopathy.

neuroscience↗