Anti-IgLON5 disease is an autoimmune disease, in which autoantibodies (AABs) against the neuronal cell surface protein IgLON5 lead to profound brain dysfunction and Tau pathology. How α-IgLON5 AABs cause neuronal Tau protein pathology and neurodegeneration remains unclear. We find that patient-derived α-IgLON5 AABs cluster IgLON5 proteins with other cell surface proteins, leading to neuronal hyperactivity that triggers pathological Tau missorting and phosphorylation, typically observed early in Tau-related neurodegenerative diseases. In wild-type mice, α-IgLON5 AABs induce hippocampal Tau phosphorylation and neuroinflammatory responses. Our findings establish a causal link between the α-IgLON5 AABs and Tau pathology in anti-IgLON5 disease patients and highlight the role of neuronal hyperactivity as a disease-overarching driver of Tau pathology and provide a potential target for therapeutic intervention.

Insulin/IGF-1 signaling (IIS) is a master regulator of metabolism, stress resilience and cell homeostasis in multicellular organisms. In the nematode Caenorhabditis elegans, DAF-2 regulates dauer diapause, animal growth and lifespan extension in a DAF-16/FOXO-dependent manner. Here we investigated IIS in animals expressing pathogenic variants of BCL-11, an evolutionarily conserved transcription factor that has been implicated in human neurodevelopmental disorders. We found that hypomorphic bcl-11 mutations have a limited impact on C. elegans growth and survival under standard growth conditions. On the contrary, BCL-11 deficiency compromises the cytoprotective properties of daf-2 signaling upon animal exposure to stress. During embryonic development, daf-16 loss of function rescues egg hatching defects in daf-2;bcl-11 mutants, suggesting a transcriptional interplay between BCL-11 and DAF-16 in IIS-deficient animals. Together, our data suggest that BCL-11 actively regulates transcription during development, while in adult animals it is recruited in response to environmental insults to enhance stress resilience.

Although genome-wide association studies (GWAS) have uncovered many genetic variants linked to brain structure, much of its heritability still remains unexplained. Short tandem repeats (STRs) are rarely considered in GWAS but may account for part of this “missing heritability”. While the causal association of large pathogenic repeat expansions with a range of brain disorders is well established, the role of non-pathogenic STR variations in the general population is largely unknown. In this study, we systematically assessed the relationship between STR variations and brain imaging-derived phenotypes across the adult lifespan in the general population. We used targeted deep sequencing to genotype approximately 3,000 polymorphic STRs across 2,958 individuals (mean age: 54.1 years, range: 30–90 years, 57.1

Aging, a major risk factor for numerous diseases, is associated with significant transcriptional changes across organs. However, the age of onset, extent of transcriptomic changes and how they unfold are not fully understood. We performed bulk RNA sequencing on eight organs (brain, heart, kidney, liver, lung, skeletal muscle, spleen, and testis) from male C57BL/6J mice across much of the murine lifespan covering 3-, 5-, 8-, 14-, 20- and 26-month-old animals. Our analysis revealed that age-related transcriptomic shifts vary in both timing and extent, with early shifts in lung, spleen, and testis; mid-life changes in heart, kidney, and skeletal muscle; and later alterations in brain and liver. The extent of age-related transcriptomic changes ranged from very low (testis) to high (kidney, liver, spleen). A linear mixed-effects model identified genes with tissue-specific aging trajectories. By integrating hub gene analysis and functional enrichment, we uncovered aging signatures that are either tissue-specific or shared across multiple organs, including those related to immune response, mitochondrial dysfunction, extracellular matrix remodeling, and cellular senescence. This study provides a systems-level resource for advancing aging research.

T follicular helper (Tfh) cells and T follicular regulatory (Tfr) cells play critical roles in regulating the activity of the germinal center (GC), which is essential for the generation of high-affinity antibodies. In the GC, Tfh cells help B cells to proliferate and to differentiate into memory B cells and long-lived plasma cells. In contrast, Tfr cells, a specialized subset of regulatory T cells (Tregs), modulate the humoral immune response by suppressing excessive or autoreactive B-cell activity. Here, we established an in vitro differentiation protocol for mouse CD4⁺ T cells that yielded CXCR5⁺FoxP3⁺ Tfr cells that exhibited a Bcl6hiPD-1hiCD25loGITRint phenotype and were distinct from Treg and Tfh cells. Functionally, in vitro-generated Tfr cells potently suppressed Tfh cell-driven B-cell class switching to IgG1 and downregulated the expression of B-cell costimulatory ligands. While in vitro-generated Bcl6-deficient Tfh cells were impaired in providing help to B cells for efficient class switching to IgG1, in vitro-generated Bcl6-deficient Tfr cells failed to inhibit Tfh cell-driven B-cell class switching to IgG1. Mechanistically, we showed that Tfr cells emerged from FoxP3+ precursors in low-IL-2 environments through a TGF-β- and c-Maf-dependent pathway, allowing for reprogramming and reinforcement of the follicular regulatory cell program in CD4+ T cells in vitro.

Triggering receptor expressed on myeloid cells 2 (TREM2) is a central regulator of microglial activity and loss-of-function coding variants are major risk factors for late onset Alzheimer’s disease (LOAD). To better understand the molecular and functional changes associated with TREM2 signalling in microglia, we generated a TREM2 reporter mouse. In APP transgenic animals, bulk RNA-sequencing of isolated microglia sorted based on reporter expression highlighted TREM2 level-related changes in major immunometabolic pathways, and enrichment of genes in oxidative phosphorylation and cholesterol metabolism in microglia with increased TREM2 expression. Metabolic and lipidomic profiling of sorted microglia showed that, independent of Aβ pathology, TREM2 expression correlated with signatures consistent with increased cellular redox, energetics, and cholesterol homoeostasis. In accordance, metabolic activity correlated with phagocytic capacity. Finally, we performed chronic treatment with a TREM2 agonist antibody and identified a window of TREM2 expression where microglia are most responsive, thereby informing clinical applications of TREM2 agonists. TREM2 is an important AD risk factor playing essential roles in the microglial response to amyloid pathology. Here, authors show using a TREM2 reporter mouse that TREM2 levels are critical for efficacy of TREM2 agonism informing current clinical efforts.

Postmortem tissue is a vital resource for transcriptomic studies of human microglia, yet the influence of postmortem delay (PMD) on microglial states, particularly in aging, remains insufficiently understood. Here, we examined the impact of PMD in young and aged male mice, with a particular focus on aging-associated primed microglia. We performed bulk RNA sequencing on Dectin-1-high and -low microglia isolated after PMDs of 0, 6, or 12 h, with Dectin-1 serving as a marker of primed microglia. PMD did not obscure aging-associated signatures or reduce viability, but consistently altered gene expression profiles. Upregulated pathways included mitochondrial, heat-shock, and apoptosis regulation responses, while actin cytoskeleton regulation was downregulated. These effects differed between young and aged animals, and between primed and non-primed microglia, with attenuation in primed subsets. Reanalysis of human single-cell and single-nucleus datasets confirmed that PMD-associated signatures identified in our dataset, particularly those in aging-related Dectin-1low microglia, correlate with PMD in human datasets and display similar enrichment patterns. Morphological analysis in fixed brain tissue from the same animals revealed that postmortem delay reduced the cell shape complexity of cortical microglia in young mice, mimicking morphological changes in the aged brain. In contrast, the morphology of aged microglia remained unchanged by postmortem delay. Taken together, these findings suggest that postmortem delay introduces subtle yet consistent transcriptional and morphological changes in microglia that can confound the interpretation of aging- and disease-related phenotypes. These results highlight the importance of controlling for postmortem effects in studies using human postmortem tissue.

Methylation of histone (H) 3 lysine (K) 4 (H3K4) has a well-established role in innate immune responses, but the contribution of H3K4 methyltransferases Kmt2c and Kmt2d in innate immunity is incompletely understood. Using conditional knockout mouse models, we investigated how Kmt2c- and Kmt2d-deficiencies affect innate immune cell function. Through functional, transcriptomic, and metabolic analyses, we delineate the consequences of disrupted epigenetic regulation on macrophage biology. Our findings reveal that loss of Kmt2c or Kmt2d in macrophages leads to impaired pro-inflammatory cytokine response and phagocytotic capacity, as well as skewed energy metabolism toward glycolysis, highlighting the critical role of H3K4 methylation-dependent chromatin regulation in shaping innate immune cell behavior. This study provides the first comprehensive characterization of innate immune system dysfunction in mouse models with conditional Kmt2c and Kmt2d deletions and offers mechanistic insight into how epigenetic regulators control fundamental immune processes.

Stem-cell-based in vitro models offer promising potential to elucidate human brain cell functions and interactions under physiological and pathological conditions. However, harnessing this potential is impaired by low reproducibility, maturity, or cell-type diversity of existing models. Especially, prolonged incorporation of mature microglia and studies of neuroinflammation have proven challenging. Here, we developed a 3D cortical brain tissue model (3BTM) containing neurons, astrocytes, and microglia with high reproducibility, maturity, and viability. 3BTMs show morphological, functional, and proteomic maturation of all cell types, leading to high similarity to their in vivo counterparts. Incorporated microglia survive for over 6 months and display mature morphology, functions, and gene expression. Importantly, when engineered to model Alzheimer's disease (AD) pathology, 3BTMs recapitulate key disease hallmarks including amyloid deposition, increased phospho-Tau levels, and neuroinflammation, with microglia shifting their transcriptional landscape to disease-relevant signatures. Treatment of AD 3BTMs with anti-Aβ immunotherapy cleared deposits and largely reversed disease signatures in glia. Together, our model offers unprecedented possibilities for studying physiological and pathological states of human brain tissue and translational applications. ### Competing Interest Statement J.K., C.C.G., and D.P. have filed a patent application covering generation, maintenance, and applications of 3BTMs. D.P. is an advisor to ISAR Bioscience GmbH, Planegg. All other authors declare no competing interests. Deutsche Forschungsgemeinschaft, https://ror.org/018mejw64, EXC2145, ID 390857198, EXC2151, ID 390873048, TRR 274/1,2 project Z01 – ID 408885537 BrightFocus Foundation, ADR AD2019604S Centers of Excellence in Neurodegeneration, CoEN6005 Bundesministerium für Bildung und Forschung, FKZ: 16LW0473, FKZ: 01ED2402A Ministry of Culture and Science of North Rhine-Westphalia

Abstract Major histocompatibility complexes (MHC) govern antigen presentation and T-cell receptor (TCR) selection. Accurate in vivo modeling of human immunity therefore requires physiological human MHC–TCR interactions. Humanized NOD-scid-IL2Rγc null (NSG) mice engrafted with human CD34⁺ hematopoietic stem cells are widely used to provide preclinical platforms for the development of advanced therapies; however, interactions between murine MHC and human TCR can promote xenoreactivity and alter T-cell development. Here, we investigated how elimination of murine MHC together with different conditioning regimens shapes human T-cell maturation in vivo . CD34⁺ cells from ten cord blood donors were transplanted into conventional NSG mice or murine MHC-deficient NSG derivatives (DKO) following either sublethal irradiation or myeloablative busulfan conditioning. Integrated analyses combining flow cytometry, plasma cytokine profiling, and bulk and single-cell TCR sequencing revealed marked differences in T-cell differentiation across models. Busulfan-conditioned DKO mice developed highly proliferative, activated, and cytotoxic T cells together with clonally expanded TCR repertoires. In contrast, irradiated NSG mice preferentially accumulated naïve, NKT, and regulatory T-cell populations. Busulfan-conditioned DKO mice showed no evidence of xenogeneic graft-versus-host disease and represent a refined enabling platform for human T-cell development and provide a foundation for future preclinical evaluation of advanced gene and cell therapies.

Abstract Naturally occurring pain and itch disorders in the domestic dog represent an important and underexploited opportunity for translational sensory neuroscience. These conditions largely mirror human disease, highlighting the need for detailed comparative understanding of canine somatosensory neurobiology. Here, we present a single-cell transcriptomic characterisation of the canine dorsal root ganglion (DRG), providing molecular insights into sensory neuron diversity in a species of direct veterinary and biomedical relevance. We develop a novel mechanical dissociation and fluorescence-activated cell sorting strategy enabling purification of intact whole neurons from adult canine DRG, followed by deep, full-length RNA sequencing using FLASH-seq. This approach yields high-quality transcriptional profiles with molecular depth analogous to deep neuronal profiling in human DRG, enabling resolution of neuronal identities and subtype-specific gene programs. Using these data, we identify canine sensory neuron clusters conforming to conserved principles of DRG molecular organization observed across species, including peptidergic and noncanonical peptidergic nociceptors, low-threshold mechanoreceptors, proprioceptors, and thermosensory populations. Cross-species comparisons with human and mouse DRG datasets reveal broad conservation of pain- and itch-relevant pathways and therapeutic targets, alongside biologically meaningful divergence. We further identify species-specific differences in subtype-restricted expression of the pharmacologically relevant receptors IL31RA and SSTR2 , which we validate using in situ hybridization and contextualize with human spatial transcriptomic data. Finally, we provide evidence that domestication-associated genes are nonrandomly enriched in specific sensory neurons, suggesting that evolutionary history may have shaped somatosensory function. These data represent a resource for comparative sensory neuroscience and inform translational interpretation of pain and itch therapeutics across species.

T follicular helper (Tfh) cells are a specialized subset of CD4⁺ T cells that localize to germinal centers (GC), where they provide critical help to B cells through the delivery of IL-21 and other cytokines. Here, we demonstrate that the tight control of the chromatin remodeler Special AT-rich sequence-binding protein 1 (Satb1) is key for this process, as overexpression of Satb1 drives lymphoproliferation and expansion of the T cell and B cell compartments in secondary lymphoid organs. Specifically, Satb1 overexpression induces a pronounced shift towards Tfh cell differentiation and increased GC formation accompanied by an increase in non-classed switched GC B cells and auto-antibody secretion. These findings highlight the importance of the precise regulation of Satb1 in fine-tuning CD4⁺ T cells and B cells responses and suggest a potential role for dysregulation of Satb1 in the pathogenesis of autoimmune disease such as systemic lupus erythematodes (SLE). ### Competing Interest Statement The authors have declared no competing interest. German Research Foundation (DFG), SFB1454 project number 432325352, IGK2168/2 project number 272482170, EXC2151 project number 390873048 European Union’s Horizon 2020 research and innovation program, project number 101163024, POLIS

Circulating innate lymphoid cells (cILCs) comprise a complex mixture of subsets with effector functions and progenitor potential toward mature ILCs and natural killer (NK) cells. Here, we dissected cord blood (CB) cILC complexity using single-cell RNA sequencing (RNA-seq) combined with developmental and functional analyses. cILC1s comprise six different subsets, with four showing different maturation degrees and two resembling NK cell progenitors. Despite previously described transcriptional similarity to T cells, the developmental potential of cILC1s was restricted to NK cells using an artificial thymic organoid (ATO) model. cILC2s could be divided into four main subsets: CD161+, CD117+, activated cILC2s, and cytotoxic cILC2s. Finally, a CD161+CD28+CD117low ILC3 subset was identified that secreted IFNγ upon co-stimulation with a CD28 superagonist, suggesting an alternative activation stimulus for cILC3s. Altogether, this in-depth analysis provides a detailed picture of cILC diversity in immunologically naive CB and constitutes a versatile resource for further exploration of their translational potential.

Microglia are highly plastic cells that are capable of integrating subsequent insults. As the majority of Alzheimer’s Disease (AD) patients also show cerebrovascular pathology, we here aimed to dissect the interactions between AD and ischemic brain injury on the microglial response to amyloid beta (Aβ) pathology. Unexpectedly, ischemic stroke in the context of cerebral β-amyloidosis drives the emergence of a neuroprotective microglial phenotype characterized by an ApoE-enriched transcriptional state and enhanced lipid handling. These microglia promote the rapid formation of highly compact Aβ plaques that are relatively inert and strikingly reminiscent of those observed in cognitively resilient AD patients. Our findings thus reveal that the microglial response to Aβ pathology is not a fixed trajectory toward dysfunction, but retains a capacity for beneficial reprogramming when engaged by the appropriate stimulus. Beyond characterizing this comorbid state, our data identify specific molecular pathways, centered on ApoE, complement activation, and lysosomal processing, that may be amenable to therapeutic targeting to promote protective microglial function in AD.

The role of the peripheral immune system in Alzheimer’s Disease (AD) remains insufficiently resolved, limiting the understanding of systemic disease effects and mechanisms. Here, we employed three high-resolution single-cell techniques, including flow cytometry, single-cell RNA- and ATAC-sequencing, to investigate peripheral immunity in AD dementia and earlier stages of the AD trajectory in over 100 patients. We identified reduced humoral immune responses in AD, characterized by a diminished B cell compartment displaying an impaired activation phenotype. Classical monocytes expanded in mild cognitive impairment and early AD dementia, acquiring a NF-kB/AP-1-mediated low-grade inflammation phenotype. Our findings link peripheral dysregulation in innate and adaptive immunity at cell frequency, transcriptional and epigenetic levels to the AD trajectory and provide insights into distinct phenotypes that define AD progression in contrast to healthy aging across cohorts. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by the National Dementia Strategy for Germany. MDB is supported by the Helmholtz Association and the German Research Foundation (DFG) (SFB1454 project number 432325352, IGK2168/2 project number 272482170). LB, ACA, MB, TU, JLS and MDB are members of the excellence cluster ImmunoSensation2 (EXC2151 project number 390873048). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All participants or their representatives provided informed consent. Ethics committees of the medical faculties of all participating sites - the ethical committees of Berlin (Charité, University Medicine), Bonn, Cologne, Göttingen, Magdeburg, Munich (Ludwig-Maximilians-University), Rostock, and Tübingen - gave ethical approval for this work. The process was led and coordinated by the ethical committee of the medical faculty of the University of Bonn. The registration number of the trial at the ethical committee in Bonn is 117/13 (please refer to Jessen, F., Spottke, A., Boecker, H., Brosseron, F., Buerger, K., Catak, C., Fliessbach, K., Franke, C., Fuentes, M., Heneka, M.T., et al., 2018. Design and first baseline data of the DZNE multicenter observational study on predementia Alzheimers disease (DELCODE). Alzheimers Res Ther 10, 15. 10.1186/s13195-017-0314-2). The ethics committee of the medical faculty of the University of Bonn gave ethical approval for the analysis of single-cell RNA-seq data under 227/19. DELCODE and DESCRIBE were conducted in accordance with the Helsinki Declaration from 1975. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes scRNA-seq, scATAC-seq and MCFC data are deposited at the DZNE Clinical Research Platform. Code will be deposited at Zenodo and will be available as of the date of publication. Any additional information required for data reanalysis is available from the lead contact upon request.

Incomplete genotype-phenotype correlations challenge the management of non-SCID FOXN1 immunodeficiency. We describe the detailed clinical course of three distinct newborns with four novel FOXN1 mutations identified by TRECNBS. For comprehensive immune characterization advanced flow cytometry-based immunophenotyping was employed alongside high-resolution single-cell RNA sequencing. In our cohort, we detected heterozygous FOXN1 mutations in P1 (c.1178delG; p.Gly393Alafs*157) and P2 (c.830+1G>T; p.?), and compound heterozygous FOXN1-mutations in P3 (c.1318C>T; p.Gln440* and c.668T>G; p.?). Despite slow and partial recovery from T-cell lymphocytopenia in P3, clinical signs for classical 'nude SCID` were incomplete. Compared to a healthy cord blood control, a distinct B-cell population was identified in the FOXN1-deficient patients expressing immature B-cell markers and lower HLA-II mRNA levels. In summary, our cohort of three newborns with four novel FOXN1 variants highlights heterogeneous immunological courses and broader thymic dysfunction implications in this rare disease. Structured management strategies are essential for those identified by NBS-programs.

Stem-cell-based in vitro models offer promising potential to elucidate human brain cell functions and interactions, but limitations in reproducibility, maturation and cell-type diversity persist. Especially, prolonged incorporation of mature microglia and studies of neuroinflammation have proven challenging. Here, we developed a human induced pluripotent stem cell-based three-dimensional cortical brain tissue model (3BTM) containing neurons, astrocytes and microglia with high reproducibility, maturity and viability. 3BTMs show morphological, functional and proteomic maturation of all cell types, leading to high similarity to their in vivo counterparts. Incorporated microglia survive for over 6 months and display mature morphology, functions and gene expression. Importantly, when engineered to model Alzheimer's disease pathology, 3BTMs recapitulate key disease hallmarks, including amyloid deposition, increased phospho-tau levels and neuroinflammation, with microglia shifting their transcriptional landscape to disease-relevant signatures. Treatment of Alzheimer's disease 3BTMs with anti-Aβ immunotherapy cleared deposits and largely reversed disease signatures in glia. Together, our microglia-containing model provides a platform for studying physiological and pathological states of human brain tissue.

The brain-nose interface is an anatomical junction where olfactory neurons from the olfactory bulb traverse the cribriform plate into the nasal mucosa, providing minimally invasive access to the central nervous system (CNS). We hypothesized that nasal fluid from this region could enable detection of neurology-relevant proteins using targeted multiplex assays. Using nosecollect, a targeted nasal sampling device, nasal fluid proximal to brain-nose interface was collected from cognitively impaired patients, alongside matched cerebrospinal fluid (CSF) and plasma. After nasal sample-specific dilution optimization and intra-assay precision evaluation, all matrices were profiled with the Olink Target 96 Neurology and NUcleic acid Linked Immuno-Sandwich Assay CNS disease 120 (NULISAseq CNS Disease 120) panels. Nasal fluid showed technically repeatable detection (intra-assay coefficient of variation <10% for more than 60% of proteins). Target detectability in nasal fluid (Olink 89/92; NULISA 121/131 proteins) was comparable to plasma and exceeded CSF. Numerous disease-relevant proteins were observed in nasal fluid, including brain-derived tau species, phosphorylated tau, alpha-synuclein, axonal and synaptic markers, and glial-microglial mediators. To our knowledge, this is the first neurology-focused characterization of the nasal proteome from the vicinity of brain-nose interface using targeted multiplex platforms and the first to profile matched nasal fluid, CSF, and plasma, supporting nasal fluid from brain-nose interface as an additional source for biomarker development. ### Competing Interest Statement MoB, MaB, SK, RM, MSN and SM are employees at Noselab GmbH, Munich Germany. HW and GW are previous employees at Noselab GmbH. MA is founder and employee of Noselab GmbH. This study is funded by Noselab GmbH, Munich. ### Clinical Trial NCT05791552 ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Participants were enrolled in the clinical study with Ethics Committee approval by Ethik-Kommission der Bayerischen Landesaerztekammer (approval number 21112; date of approval: 03-FEB-2022), and the study has been registered on ClinicalTrials.gov (ClinicalTrials.gov identifier: [NCT05791552][1]). This study was conducted in accordance with the principles of the Declaration of Helsinki. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors and completion of a data use agreement. Noselab GmbH, Munich, Germany [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT05791552&atom=%2Fmedrxiv%2Fearly%2F2026%2F06%2F17%2F2026.06.16.26355519.atom

Animal lifespan depends on coordinated gene expression networks that regulate metabolic adaptation, proteostasis, and stress resilience in response to environmental challenges. Histone variants are key regulators of chromatin dynamics, orchestrating nucleosome remodeling, DNA accessibility, and gene expression. While the role of histone H3.3 in aging and animal survival has been explored across model systems, the contribution of other replication-independent histone variants remains less well-defined. Here, we demonstrate that the evolutionarily conserved histone variant HTZ-1/H2A.Z is essential for organismal survival. In the nematode Caenorhabditis elegans, loss of HTZ-1/H2A.Z disrupts gene expression programs associated with longevity, including those activated in insulin/IGF-1 deficient daf-2 mutants and in mitochondrial Complex I deficient animals. Together, our findings show that HTZ-1/H2A.Z regulates gene expression programs that coordinate metabolic and proteostatic pathways, thereby fine-tuning stress responses and promoting lifespan in animals.

Aging-associated loss of chromatin compaction is linked to derepression of retrotransposable elements (RTEs) in mouse and human tissues. Whether such RTE transcription contributes to the microglia activation that is common in aged brains is unknown. Here, we show that DAXX, a histone chaperone and RTE repressor, is downregulated during aging, preserves microglia homeostasis and inhibits cellular senescence. Loss of Daxx in young-adult microglia drives a reactive phenotype marked by chromatin decompaction at RTEs, loss of homeostatic markers, cell cycle re-entry and behavioral changes. This state leads to DNA damage and microglial depletion, followed by replacement with DAXX-deficient/Apoehigh microglia displaying features of senescence. Sustained induction of senescence relies on promyelocytic leukemia protein, a DAXX-interacting factor and interferon target. Together, these findings highlight the importance of heterochromatin maintenance in preserving adult microglial identity and plasticity, with broader implications for brain homeostasis, healthy aging and behavior.