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Hepatitis E virus (HEV) is a significant human pathogen causing both acute and chronic infections worldwide. The cell-intrinsic antiviral response serves as the initial defense against viruses and has been shown to be activated upon HEV infection. HEV can replicate in the presence of this response, but the underlying mechanisms remain poorly understood. Here, we investigated the roles of the structural proteins ORF2 and ORF3 in the cell-intrinsic antiviral response to HEV infection. Mechanistically, we validated that ectopic ORF2, but not ORF3, interfered with antiviral and inflammatory signaling downstream of pattern recognition receptors, in part through interaction with the central adaptor protein TANK binding kinase 1. In the full-length viral context, ORF2 contributed to a reduced antiviral response and consequently, more efficient viral replication. In addition, we discovered a protective mechanism mediated by ORF2 that shielded viral replication from antiviral effectors. Using single-cell RNA-sequencing, we confirmed that the presence of ORF2 in infected cells dampened antiviral responses in both actively infected cells and bystanders. As a consequence, we found that early in the infection process, the progression of authentic HEV infection relied on the presence of ORF2, facilitating a balance between viral replication and the antiviral response. Altogether, our findings shed new light on the multifaceted role of ORF2 in the HEV life cycle and improve our understanding of the determinants that contribute to persistent HEV replication in cell culture. Author summaryHepatitis E virus (HEV) is an important yet often underestimated pathogen. Depending on the genotype, HEV infections can progress to chronicity, but the underlying mechanisms remain poorly understood. To gain insight into potential determinants, we investigated how HEV evades the cell-intrinsic antiviral response. We discovered that the HEV capsid protein ORF2 is crucial in limiting this response by interfering with antiviral signaling pathways and shielding viral replication from immune effectors. This balance between viral replication and the antiviral response contributes to persistent HEV infection in cell culture. Our findings reveal a new role for the HEV capsid protein in the viral life cycle and highlight it as an important target for novel therapeutic approaches.

The rare and rapidly progressive neurodegenerative disease multiple system atrophy (MSA) mainly affects the striatum and other subcortical brain regions. In this atypical Parkinsonian syndrome, the protein alpha-synuclein aggregates and misfolds in neurons as well as glial cells and is released in elevated amounts by hypoexcitable neurons. Mitochondrial dysregulation affects the biosynthesis of coenzyme Q10 and the activity of the respiratory chain, as shown in an induced pluripotent stem cell (iPSC) model. Proteome studies of cerebrospinal fluid and brain tissue from MSA patients yielded inconsistent results regarding possible protein changes due to small and combined groups of atypical Parkinsonian syndromes. In this study, we analysed the cellular proteome of MSA patient-derived striatal GABAergic medium spiny neurons. We observed 25 significantly upregulated and 16 significantly downregulated proteins in MSA cell lines compared to matched healthy controls. Various protein types involved in diverse molecular functions and cellular processes emphasise the multifaceted pathomechanisms of MSA. These data could contribute to the development of novel disease-modifying treatment strategies for MSA patients.

Alpha-synuclein (aSyn) post-translational modifications (PTM), especially phosphorylation at serine 129 and C-terminal truncations, are highly enriched in Lewy bodies (LB), Lewy neurites, and other pathological aggregates in Parkinson’s disease and synucleinopathies. However, the precise role of these PTM in pathology formation, neurodegeneration, and pathology spreading remains unclear. Here, we systematically investigated the role of post-fibrillization C-terminal aSyn truncations in regulating uptake, processing, seeding, and LB-like inclusion formation using a neuronal seeding model that recapitulates LB formation and neurodegeneration. We show that C-terminal cleavage of aSyn fibrils occurs rapidly post exogenous fibril internalization and during intracellular LB-like inclusion formation. Blocking cleavage of internalized fibrils does not affect seeding, but inhibiting enzymes such as calpains 1 and 2 alters LB-like inclusion formation. We show that C-terminal truncations, along with other PTMs, regulate fibril interactome remodeling, shortening, lateral association, and packing. These findings reveal distinct roles of C-terminal truncations at different aggregation stages on the pathway to LB formation, highlighting the need for consideration of stage‑specific strategies to target aSyn proteolytic cleavages.

Variants of phospholipase C gamma 2 (PLCG2), a key microglial immune signaling protein, are genetically linked to Alzheimer's disease (AD) risk. Understanding how PLCG2 variants alter microglial function is critical for identifying mechanisms that drive neurodegeneration or resiliency in AD. Induced pluripotent stem cell (iPSC) –derived microglia carrying the protective PLCG2 P522R or risk‐conferring PLCG2 M28L variants, or loss of PLCG2, were generated to ascertain the impact on microglial transcriptome and function. Protective PLCG2 P522R microglia showed significant transcriptomic similarity to isogenic controls. In contrast, risk‐conferring PLCG2 M28L microglia shared similarities with PLCG2 KO microglia, with functionally reduced TREM2 expression, blunted inflammatory responses, and increased proliferation and cell death. Uniquely, PLCG2 P522R microglia showed elevated cytokine secretion after lipopolysaccharide (LPS) stimulation and were protected from apoptosis. These findings demonstrate that PLCG2 variants drive distinct microglia transcriptomes that influence microglial functional responses that could contribute to AD risk and protection. Targeting PLCG2‐mediated signaling may represent a powerful therapeutic strategy to modulate neuroinflammation. The impact of Alzheimer's disease protective‐ and risk‐associated variants of phospholipase C gamma 2 (PLCG2) on the transcriptome and function of induced pluripotent stem cell (iPSC) –derived microglia was investigated. PLCG2 risk variant microglia exhibited a basal transcriptional profile similar to PLCG2‐deficient microglia but significantly different from isotype control and the transcriptionally similar PLCG2 protective variant microglia. PLCG2 risk variant and PLCG2‐deficient microglia show decreased levels of triggering receptor expressed on myeloid cells 2 (TREM2). The differential transcriptional pathways of protective and risk‐associated PLCG2 variant microglia functionally affect proliferation, apoptosis, and immune response. Protective PLCG2 microglia show resilience to apoptosis and increased cytokine/chemokine secretion upon exposure to lipopolysaccharide (LPS).

Understanding diseases as the result of continuous transitions from a healthy system is more realistic than understanding them as discrete states. Here, we designed the spectrum formation approach (SFA), a machine learning-based method that extracts key features contributing to disease state continuity. We applied the SFA to transcriptomic data from patients with progressive liver disease and neurodegenerative movement disorders to examine its effectiveness in identifying biologically relevant gene sets. The SFA identified transcription factors that potentially regulate liver inflammation and voluntary movement. In neurodegenerative disorders, the SFA also identified genes regulated by ETS-1, with unclear effects on movement. In functional assessment using human iPSC-derived neurons, ETS-1 overexpression disrupted dopamine receptor balance, reduced GABA-producing enzyme levels, and promoted cell death. These findings suggest that the SFA enables the discovery of regulatory factors capable of modifying disease states and provides a framework for the continuity-based interpretation of biological systems. Subject terms: Diseases, Pathogenesis, Signs and symptoms

Brain organoids derived from human pluripotent stem cells (hPSCs) hold immense potential for modeling neurodevelopmental processes and disorders. However, their experimental variability and undefined organoid selection criteria for analysis hinder reproducibility. As part of the Bavarian ForInter consortium, we generated 72 brain organoids from distinct hPSC lines. We conducted a comprehensive analysis of their morphological and cellular characteristics at an early stage of their development. In our assessment, the Feret diameter emerged as a reliable, single parameter that characterizes brain organoid quality. Transcriptomic analysis of our organoid identified the abundance of unintended mesodermal differentiation as a major confounder of unguided brain organoid differentiation, correlating with Feret diameter. High-quality organoids consistently displayed a lower presence of mesenchymal cells. These findings provide a framework for enhancing brain organoid standardization and reproducibility, underscoring the need for morphological quality controls and considering the influence of mesenchymal cells on organoid-based modeling. Subject terms: Mesenchymal stem cells, Induced pluripotent stem cells, Stem-cell differentiation

Differentiation of embryonic stem cells and induced pluripotent stem cells (iPSCs) into endoderm derivatives, including thyroid, thymus, lungs, liver, and pancreas, has broad implications for disease modeling and therapy. We utilize and expand a model development approach previously outlined by the authors to construct a model for the directed differentiation of iPSCs into definitive endoderm (DE). Assuming discrete intermediate stages in the differentiation process with a homogeneous population in each stage, three lineage models with two, three, and four populations and three growth models are constructed. Additionally, three models for error distribution are defined, resulting in a total of 27 models. Experimental data obtained in vitro are used for model calibration, model selection, and final validation. Model selection suggests that no transitory state during differentiation expresses the DE biomarkers CD117 and CD184, a finding corroborated by existing literature. Additionally, space-limited growth models, such as logistic and Gompertz growth, outperform exponential growth. Validation of the inferred model with leave-out data results in prediction errors of 26.4%. Using the inferred model, it is predicted that the optimal differentiation period is between 1.9 and 2.4 days, plating populations closer to 300 000 cells per well result in the highest yield efficiency, and that iPSC differentiation outpaces the DE proliferation as the main driver of the population dynamics. We also demonstrate that the model can predict the effect of growth modulators on cell population dynamics. Our model serves as a valuable tool for optimizing differentiation protocols, providing insights into developmental biology.

INTRODUCTIONPolygenic risk score (PRS) identifies individuals at high genetic risk for Alzheimer's disease (AD), but its utility in predicting cognitive trajectories and AD pathologies remains unclear. We optimized PRS (optPRS) for AD, investigated its association with cognitive trajectories and AD phenotypes of cerebral organoids.METHODSUsing genome‐wide association study (GWAS) summary statistics from a European population, we developed optPRS to predict AD in Korean individuals (n = 1634). We analyzed the association between optPRS and cognitive trajectories (n = 771). We generated induced pluripotent stem cell–derived cerebral organoids from patients with high (n = 3) and low (n = 4) optPRS to evaluate amyloid beta (Aβ) and phosphorylated tau (p‐tau) levels.RESULTSOptPRS predicted AD dementia and Aβ positivity, independent of apolipoprotein E (APOE). Higher optPRSs correlated with rapid cognitive decline. Cerebral organoids from the high optPRS group exhibited increased Aβ insolubility and p‐tau levels.CONCLUSIONOptPRS predicted cognitive decline and AD phenotypes of cerebral organoids, supporting its use in risk assessments and drug‐screening platform.Highlights Optimized polygenic risk scores (optPRSs) improve the prediction of Alzheimer's disease (AD) dementia and amyloid beta positivity (Aβ+).High optPRS is associated with faster cognitive decline, particularly in Aβ+.Induced pluripotent stem cell (iPSC)–derived cerebral organoids from high optPRSs show high Aβ insolubility and phosphorylated tau (p‐tau).PRS genetic risk stratification provides insight into AD progression and pathology.

Autism Spectrum Disorder (ASD) is a neurodevelopmental condition that affects communication, social interaction, and behavior. Calcium (Ca2+) signaling dysregulation has been frequently highlighted in genetic studies as a contributing factor to aberrant developmental processes in ASD. Herein, we used ASD and control induced pluripotent stem cells (iPSCs) to investigate transcriptomic and functional Ca2+ dynamics at various stages of differentiation to cortical neurons. Idiopathic ASD and control iPSC lines underwent the dual SMAD inhibition differentiation protocol to direct their fate toward cortical neurons. Samples from multiple time points along the course of differentiation were processed for bulk RNA sequencing, spanning the following sequential stages: the iPSC stage, neural induction (NI) stage, neurosphere (NSP) stage, and differentiated cortical neuron (Diff) stage. Our transcriptomic analyses suggested that the numbers of Ca2+ signaling-relevant differentially expressed genes between ASD and control samples were higher in the iPSC and Diff stages. Accordingly, samples from the iPSC and Diff stages were processed for Ca2+ imaging studies. Results revealed that iPSC-stage ASD samples displayed elevated maximum Ca2+ levels in response to ATP compared to controls. By contrast, in the Diff stage, ASD neurons showed reduced maximum Ca2+ levels in response to ATP but increased maximum Ca2+ levels in response to KCl and DHPG relative to controls. Considering the distinct functional signaling contexts of these stimuli, this differential profile of receptor- and ionophore-mediated Ca2+ response suggests that aberrant calcium homeostasis underlies the pathophysiology of ASD neurons. Our data provides functional evidence for Ca2+ signaling dysregulation during neurogenesis in idiopathic ASD.

Long-term imaging formats are ideal for capturing dynamic neuronal network formation in vitro, yet fluorescent techniques are often constrained by the impact of phototoxicity on cell survival. Here we present a live-imaging protocol that was optimised via quantitative analysis of 3 target culturing conditions on neuromorphological health: extracellular matrix (human- versus murine-derived laminin), culture media (Neurobasal™ versus Brainphys™ Imaging media), and seeding density (1 × 105 versus 2 × 105 cells/cm2). A cortical neuron reporter line was differentiated from human embryonic stem cells by transduction of Neurogenin-2 and green fluorescent protein, then fluorescently imaged in 8 different microenvironments daily for 33 days. Alongside viability analysis by PrestoBlue assay and gene quantification by digital polymerase chain reaction, an automated image analysis pipeline was developed to characterise network morphology and organisation over time. Brainphys™ Imaging medium was observed to support neuron viability, outgrowth, and self-organisation to a greater extent than Neurobasal™ medium with either laminin type, while the combination of Neurobasal™ medium and human laminin reduced cell survival. Further, a higher seeding density fostered somata clustering, but did not significantly extend viability compared to low density. These findings suggest a synergistic relationship between species-specific laminin and culture media in phototoxic environments, which is positively mediated by light-protective compounds found in Brainphys™ Imaging medium.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13287-025-04591-0.

MYCN amplification without concurrent RB1 mutations characterizes a rare yet highly aggressive subtype of retinoblastoma; however, its precise developmental origins and therapeutic vulnerabilities remain incompletely understood. Here, we modeled this subtype by lentiviral-mediated MYCN overexpression in human pluripotent stem cell-derived retinal organoids, revealing a discrete developmental window (days 70–120) during which retinal progenitors showed heightened susceptibility to transformation. Tumors arising in this period exhibited robust proliferation, expressed SOX2, and lacked CRX, consistent with origin from primitive retinal progenitors. MYCN-overexpressing organoids generated stable cell lines that reproducibly gave rise to MYCN-driven tumors when xenografted into immunodeficient mice. Transcriptomic profiling demonstrated that MYCN-overexpressing organoids closely recapitulated molecular features of patient-derived MYCN-amplified retinoblastomas, particularly through activation of MYC/E2F and mTORC1 signaling pathways. Pharmacological screening further identified distinct therapeutic vulnerabilities, demonstrating distinct subtype-specific sensitivity of MYCN-driven cells to transcriptional inhibitors (THZ1, Flavopiridol) and the cell-cycle inhibitor Volasertib, indicative of a unique oncogene-addicted state compared to RB1-deficient retinoblastoma cells. Collectively, our study elucidates the developmental and molecular mechanisms underpinning MYCN-driven retinoblastoma, establishes a robust and clinically relevant human retinal organoid platform, and highlights targeted transcriptional inhibition as a promising therapeutic approach for this aggressive pediatric cancer subtype.

BackgroundDiabetic peripheral neuropathy (DPN) is one of the most prevalent and debilitating complications of diabetes, marked by chronic neuroinflammation, immune dysregulation, and progressive neuronal degeneration. Current treatments offer limited efficacy, largely focusing on symptomatic relief rather than addressing the underlying disease mechanisms. There is a critical need for disease-modifying therapies that target the molecular basis of DPN.ResultsIn this study, we developed a novel targeted nanotherapeutic system—ZH-1c-EVs@SIN—composed of neural stem cell-derived extracellular vesicles (NSC-EVs) modified with the ZH-1c aptamer and loaded with the anti-inflammatory compound sinomenine (SIN). This system was specifically designed to target microglia and inhibit the WNT5a/TRPV1 signaling pathway. Transcriptomic profiling of microglia revealed key gene networks implicated in DPN pathology and responsive to SIN treatment. Functional assays demonstrated that ZH-1c-EVs@SIN facilitated a shift in microglial phenotype from pro-inflammatory M1 to anti-inflammatory M2, significantly reduced inflammatory cytokine expression, and restored levels of neuronal regulatory proteins. Nanoparticle tracking analysis and transmission electron microscopy confirmed optimal vesicle size and morphology, while fluorescence imaging showed efficient uptake by microglia. In vivo studies in a murine model of DPN revealed marked improvements in pain-related behavior and histopathological signs of nerve damage.ConclusionZH-1c-EVs@SIN represents a promising therapeutic strategy for DPN, offering targeted immunomodulation and enhanced neural repair via regulation of the WNT5a/TRPV1 signaling axis. This nano-delivery platform introduces a novel and precise approach to intervening in diabetic neuropathy and may be applicable to other neuroinflammatory conditions.Graphical abstractMechanism of ZH-1c-EVs@SIN Mediating the WNT5a/TRPV1 Pathway to Improve Immune-Inflammatory Homeostasis in the Treatment of DPN in Mice. Supplementary InformationThe online version contains supplementary material available at 10.1186/s12951-025-03678-3.