Blood

Severe hemolysis is a life-threatening condition with limited therapeutic options. Although haptoglobin and hemopexin sequester hemoglobin and heme, these protective systems are rapidly saturated during acute hemolysis, leading to the accumulation of cytotoxic free heme. In this study, we identify scavenger receptor BI (SR-BI) as a critical mediator of free heme clearance. SR-BI binds heme and facilitates its hepatic uptake under pathological conditions. Mice lacking hepatic SR-BI exhibit impaired heme clearance and increased susceptibility to heme- and hemolysis-induced lethality. Pharmacological upregulation of hepatic SR-BI via imatinib or adenoviral delivery confers protection against heme toxicity. Using a humanized model of sickle cell disease (SCD), we further demonstrate that sickle hepatopathy significantly reduces hepatic SR-BI expression compared to non-SCD littermates, potentially increasing vulnerability to heme-induced injury. Notably, adenoviral-mediated SR-BI upregulation rescues SCD mice from heme toxicity. These findings reveal a previously unrecognized mechanism of heme detoxification via hepatic SR-BI and identify a promising therapeutic target for hemolytic disorders. One-Sentence SummaryIdentification of scavenger receptor BI as a targetable scavenger of heme in hemolysis

Multiple myeloma (MM) is a clonal plasma cell malignancy characterized by bone marrow infiltration, monoclonal immunoglobulin production, and microenvironmental dysregulation that leads to systemic organ damage. The advent of B-cell maturation antigen (BCMA)-directed chimeric antigen receptor (CAR) T-cell therapy has induced unprecedented responses and durability for patients with relapsed/refractory MM. These outcomes are rarely observed with prior salvage strategies, although relapse remains the predominant long-term challenge for most patients. The two currently approved BCMA CAR-T cell products use viral vectors to semi-randomly insert the CAR gene, which results in heterogeneous genomic composition and variability in efficacy, safety, and product consistency. To address these challenges, we integrated targeted CRISPR genome engineering with precise CAR transgene insertion at the T-cell receptor alpha constant (TRAC) locus, 1XX CAR signaling architecture to enhance potency and durability, and non-viral manufacturing with a single-stranded DNA repair template to improve efficiency and yield. This approach confers physiological CAR expression, reduces insertional mutagenesis, and improves persistence by mitigating tonic signaling and exhaustion. Our GMP manufacturing process consistently achieved high CAR integration (37.7-72.7%) and yields across all full-scale runs and met predefined release criteria for identity, purity, safety, and quality. In NSG mouse models of MM, the UCCT-BCMA-1 product exhibited exceptionally potent tumor control, CAR-T cell expansion 100-1000-fold greater than that of lentiviral constructs, and durable clearance of myeloma cells after multiple rechallenges. These findings establish a CRISPR-edited, fully non-viral manufacturing platform for next-generation 1XX-BCMA CAR-T therapies with enhanced persistence, safety, and efficacy. One Sentence SummaryCRISPR-engineered, TRAC-targeted 1XX-BCMA CAR-T therapy with improved safety, potency, and persistence in relapsed and refractory multiple myeloma.

Human Fc receptor-like 5 (FCRL5) is a low-affinity IgG Fc receptor expressed on various B cell subsets and a potential therapeutic target. We discovered that commonly used Fc-silencing mutations, designed to prevent interactions between the Fc{gamma} receptors on immune cells and the Fc domain of therapeutic IgG, do not prevent binding to FCRL5. As a result, unintended interactions between Fc-silent therapeutic IgG and human B cells may occur. We isolated a well-expressed variant of the Fc-binding portion of human FCRL5 by directed evolution and used structural modeling to guide the engineering of a human IgG1 Fc variant with approximately 100-fold higher affinity for FCRL5, enabling us to produce FCRL5:Fc complexes in solution. Native mass spectrometry, size exclusion chromatography, and the crystal structure of the FCRL5- IgG1 Fc complex solved at 3.4 [A] indicate that the two proteins bind in a 1:1 stoichiometry. Furthermore, the structure revealed that FCRL5 binds to IgG1 Fc in a manner completely distinct from that of previously characterized Fc-binding proteins, such as Fc{gamma} receptors, explaining why most Fc-silencing mutations do not disrupt FCRL5 binding. We demonstrate that selective cross-linking of FCRL5 with the B cell receptor (BCR) in cis, using Fc-engineered antibodies with either physiological or enhanced FCRL5 affinity, inhibits Ca2+ flux in FCRL5-expressing B cells. We compare this effect with the selective co-ligation of Fc{gamma}RIIb with the BCR. Our work demonstrates that FCRL5 interacts with human IgG Fc in a distinctive manner and that engagement of FCRL5 by Fc-silent therapeutic IgG could influence B cell function.

Diffuse Large B-cell lymphoma (DLBCL) is the most common aggressive lymphoma in the Western world. First-line immunochemotherapy fails in approximately 30-40% of patients, with refractory and relapse patients presenting a dismal prognosis. Currently, these high-risk patients cannot be accurately identified at diagnosis. Using statistical modeling and machine learning approaches applied to large public DLBCL datasets, we identified a novel predictive signature based on the reactivation of eight normally silent tissue-dependent genes associated with survival. We then developed a multiplex RT-MLPseq based assay, compatible with formalin-fixed paraffin-embedded (FFPE) samples and transferable into routine clinical practice, enabling analysis of expression of these eight genes and validated their prognosis impact in an independent real-life cohort. This signature could be integrated with current prognostic indices and molecular classifications to improve patient stratification and guide treatment selection toward a personalized theragnostic approach, thereby enhancing management of non-responder patients.

BackgroundExcessive accumulation of fibrillar collagen causes pathological scarring and fibrosis. A promising anti-fibrotic strategy targets the extracellular assembly of collagen fibrils rather than intracellular synthesis pathways. We previously developed a chimeric monoclonal antibody targeting the C-terminal telopeptide of the 2(I) chain of human collagen I that effectively disrupts fibrillogenesis. This study details the engineering of a humanized antibody variant optimized for therapeutic application, augmented with a collagen-binding peptide (CBP) to enhance targeted retention in fibrotic tissues. MethodsA humanized ACA was engineered by in silico homology modeling, complementarity-determining region grafting, and sequence optimization to eliminate chemical liabilities. Variants were expressed in mammalian cells and evaluated for binding kinetics and specificity. To improve spatial localization, the CBP was fused to the antibody. The lead variant was assessed for in vitro cytotoxicity, matrix retention, and in vivo efficacy using a rabbit model of post-traumatic knee arthrofibrosis. ResultsThe humanized ACA variants maintained high specificity and affinity for the 2Ct target domain. Fusing the CBP to the C-terminus of the light chain (C-cbpACA) successfully enhanced matrix retention without compromising target engagement or causing cellular toxicity. In the rabbit arthrofibrosis model, intra-articular C-cbpACA delivery significantly reduced flexion contracture and decreased total collagen deposition in the joint capsule compared to untreated controls. ConclusionWe successfully engineered a clinically viable, humanized, and matrix-targeted anti-fibrotic antibody that specifically inhibited extracellular collagen assembly and exhibited enhanced localization within fibrotic tissues. This construct represents a promising therapeutic strategy for mitigating pathological scarring and improving post-traumatic functional outcomes.

Aberrant expression of Long Interspersed Element-1 (LINE-1/L1) retrotransposons is increasingly linked to genomic instability in cancer, particularly in the context of compromised p53 function. The endonuclease (EN) domain of the LINE-1 ORF2 protein (ORF2p) generates DNA strand breaks, yet its role in shaping downstream chromatin and transcriptional responses remains poorly defined. Here, we investigate the impact of ORF2p-EN activity on DNA damage response signalling and epigenomic remodeling in isogenic wild-type and p53-deficient A375 melanoma cells using a L1 expression system. ORF2p-EN expression induced activation of ATM dependent DNA damage signalling, as evidenced by increased {gamma}H2AX accumulation. This response was accompanied by altered levels of the DNA repair factor XRCC5, consistent with engagement of non-homologous end joining pathways. Notably, EN-associated DNA damage correlated with increased p300 activity and enhanced H3K27ac enrichment at regulatory regions, suggesting coupling between DNA damage signalling and chromatin acetylation. Pharmacological inhibition of ATM attenuated both {gamma}H2AX accumulation and H3K27ac levels, supporting a model in which chromatin remodeling occurs downstream of DNA damage signalling. Collectively, our findings position ORF2p endonuclease activity as an initiating source of DNA damage that is functionally linked to chromatin remodeling and transcriptional reprogramming, with p53 acting as a critical modulator of this axis. These results provide mechanistic insight into how LINE-1 activation may contribute to oncogenic gene expression programs in cancer.

The heat shock transcription factor HSF1 is best known as a master regulator of the proteotoxic stress response, yet its functions in animal development remain incompletely defined. In Drosophila melanogaster, heat shock factor (HSF) is essential for viability, but the mechanisms by which it promotes development are unclear. Here, we show that Hsf null larvae arrest at the early 2nd instar stage and exhibit a significant reduction in basal levels of the chaperone HSP83. Tissue-specific knockdown of Hsf revealed widespread and organ-specific requirements, including defects in endoreplication and cell growth in larval prothoracic and salivary glands, adult wing defects following larval imaginal disc perturbation, follicle degeneration in the ovary, and melanotic tumor upon hemocyte depletion. In these tissues, loss of HSF typically leads to reduced HSP83 levels, and restoration of HSP83 expression partially or fully rescues these defects. These findings identify HSP83 as a critical downstream effector of HSF and demonstrate that HSF promotes development largely by maintaining basal chaperone expression. Together, our results establish HSF as a key regulator of developmental progression and highlight a central role for proteostasis in supporting tissue growth under non-stress conditions.

TAp63, a member of the p53 family, serves as a central quality control factor in oocytes, safeguarding genomic integrity during the prolonged dictyate arrest of meiosis. In healthy oocytes, TAp63 is maintained in an inactive dimeric state; upon DNA damage, it undergoes phosphorylation-dependent tetramerization, enabling transcriptional activation of pathways that determine oocyte fate. While the upstream activation cascade of TAp63 has been well characterized, the mechanisms that regulate its stability during the DNA damage response remain incompletely understood. Here, we identify the kinases HIPK2 and IKK{beta} as key regulators of TAp63 stability. We show that TAp63 interacts with both kinases and is phosphorylated at distinct residues, T452 by HIPK2 and S4/S12 by IKK{beta} in vitro and in vivo, in addition to previously described CHK2 and CK1-mediated phosphorylation. Functionally, these phosphorylation events do not primarily contribute to activation, but instead stabilize TAp63 by limiting MDM4-dependent ubiquitination and subsequent proteasomal degradation. Mechanistically, our data support a model in which CHK2 and CK1 initiate TAp63 phosphorylation, while HIPK2 and IKK{beta} act in a complementary manner to maintain protein stability during genotoxic stress. Disruption of HIPK2 or IKK{beta} activity reduces TAp63 stability, whereas their inhibition in vivo attenuates oocyte loss following DNA damage, resulting in increased preservation of the follicle pool. Importantly, these effects are observed across multiple systems, including mouse models and ex vivo goat ovary cultures, supporting an evolutionarily conserved role for this regulatory axis. Together, our findings uncover a previously unidentified layer of TAp63 regulation, in which phosphorylation not only contributes to its activation but also enhances protein stability, thereby fine-tuning oocyte responses to DNA damage. Our results further indicate that HIPK2 and IKK{beta}-mediated phosphorylation modulates oocyte survival under genotoxic stress, highlighting this pathway as a potential target for strategies aimed at limiting oocyte loss.

Meiosis generates haploid gametes from a diploid progenitor. In meiosis I, homologous chromosomes segregate while sister chromatids co-orient toward the same spindle pole. The mechanisms underlying this specialized segregation pattern remain incompletely understood. Here we identify pathways required for meiosis I chromosome segregation through a forward genetic screen in Saccharomyces cerevisiae. We find that meiosis I is highly sensitive to perturbations in diverse components of the segregation machinery and define key functional interfaces within complexes important for this division. These include meiosis I-specific regulators that establish the specialized chromosome pattern, namely the monopolin complex that directs sister kinetochore co-orientation and the Spo13MOKIR-Cdc5Polo module that promotes meiosis I chromosome segregation. In addition, we identify mutations affecting the core segregation machinery, including the spindle pole body, spindle midzone, and outer kinetochore, which can disrupt coupling between the chromosome segregation program and the meiotic spindle cycle. Together, our findings reveal that multiple pathways coordinate chromosome segregation with the meiotic divisions and highlight the unique demands of meiosis I.

Despite considerable advances, the emergence of treatment resistance to tyrosine kinase inhibitors (TKIs) therapy remains a significant challenge in chronic myeloid leukemia (CML). Here, we report the first clinical case of resistance to combined ponatinib and asciminib therapy in a CML patient who relapsed with B lymphoblastic blast crisis. While at presentation the patient harbored the canonical e13a2 BCR::ABL1 fusion, at relapse his disease harbored the T315I mutation together with a novel e6a3 BCR::ABL1 fusion, arisen by internal deletion in the original translocated allele. Structural modeling and biochemical analyses demonstrated that deletion of exon 2-encoded residues of ABL1 destabilizes the autoinhibited conformation, resulting in a hyperactive kinase with increased propensity for B-cell differentiation. Functional studies revealed that both BCR::ABL1e6a3 and BCR::ABL1e6a3/T315I conferred resistance to ponatinib and asciminib, alone or in combination. BCR::ABL1e6a3 demonstrated enhanced sensitivity to active-state selective inhibitors dasatinib and bosutinib, whereas BCR::ABL1e6a3/T315I remained resistant. Combined drug sensitivity assays showed that axitinib restored inhibitory activity when combined with ponatinib or asciminib. Strikingly, a combination of axitinib and asciminib with low dose ponatinib fully suppressed enzymatic activity of BCR::ABL1e6a3/T315I and cellular proliferation. These data show that treatment with asciminib and ponatinib can select for mutations with notably elevated enzymatic activity, effectively targeted by an axitinib-based triple combination. These data highlight the remarkable mutability of the BCR::ABL1 kinase, including through novel isoforms and provides a strong rationale for the clinical assessment of a triple inhibitor combination as a strategy to overcome resistance to dual ponatinib and asciminib therapy.

Certain regulatory DNA regions remain accessible even under conditions of widespread chromatin compaction. These regions are often marked by specific protein factors and histone modifications that help maintain their accessibility. Here, we examine the genomic landscape of acetyl-methyllysine (Kacme), a recently discovered histone post-translational modification. Across multiple systems, Kacme is highly enriched at sites of accessible chromatin, including active promoters, enhancers, silencers, and CTCF-binding sites. We find that Kacme is selectively retained at loci that resist condensation during mitosis, marks XIST and escapee regions on the inactive X chromosome in female cells and demarcates the boundaries of broad heterochromatin domains. Kacme-marked insulator elements block heterochromatin spreading and protect adjacent genes from transcriptional repression, even when H3K27me3 levels are pharmacologically elevated through KDM6A/6B inhibition. Taken together, our findings establish the chromatin features associated with Kacme and support a model in which Kacme helps safeguard chromatin accessibility at loci that resist compaction.

Sarcoidosis is a heterogenous disease of unknown etiology characterized by non-caseating granulomas. Disease prevalence and presentation vary significantly by ancestry and ranges from acute, self-resolving disease to severe, chronic disease. Following previous reports suggesting B cells in the development and pathogenesis of sarcoidosis, we present here results of single-cell RNA sequencing, supporting B cell involvement in sarcoidosis through altered immediate early response, rewiring of MAPK signaling, and ancestry-specific preferential expansion of B cell receptors. Peripheral blood mononuclear cells were obtained from individuals of African or European Ancestry (AA and EA, respectively) including 48 healthy controls, 59 sarcoidosis patients, and 28 systemic lupus erythematosus (SLE) patients. SLE samples were used as a disease control. Differential expression analysis highlighted many differentially expressed genes (DEGs) with almost 5x more in the AA sarcoidosis versus AA control group compared to the EA sarcoidosis versus EA control group. B cells had the most DEGs of all cell types and expression patterns were similar between ancestries, however, sarcoidosis had an opposite transcription pattern than SLE, demonstrating an alternative immune response to acute activation than that seen in a prototypical autoinflammatory disease. This trend was maintained when examining specialized B cell subsets, with the most pronounced effect in the AA sarcoidosis versus AA control comparison. Our results strongly support further investigation of the role of humoral immune response in sarcoidosis and the potential to highlight patient groups likely to benefit from existing B cell therapies.

During ageing, hematopoietic stem cells (HSCs) have reduced regenerative potential, skewed differentiation toward the myeloid lineage, and heightened susceptibility to clonal expansion and malignancy. While epigenetic alterations are well documented, the impact of aging on higher-order 3D chromatin architecture remains poorly understood. Here, we examined the 3D genome organisation of aged murine HSCs using in-situ Hi-C then integrated this with gene expression and chromatin accessibility data to build HiC-informed gene regulatory networks (GRNs). Aged HSCs display erosion of topologically associating domain (TAD) boundaries, A/B compartment switching, and reorganised enhancer-promoter loops associated with lineage-inappropriate gene expression. Our GRN analysis identifies a hierarchy of transcription factors, including a c-Maf-Lyl1-Mnt axis that orchestrates the transition from a youthful to aged state and a Gfi1-Sox4 axis in young HSCs that regulates Bach1. This study provides a structural blueprint for aging HSCs and defines specific regulatory targets for potential reprogramming interventions to restore hematopoietic youthfulness.

53BP1 nuclear bodies are dynamic and are endowed with properties that resemble biomolecular condensates, but molecular determinants that underlie transition of 53BP1 oligomerisation to its higher-order assembly at DNA double-strand breaks (DSBs) remain to be established. We found that 53BP1 condensation is stimulated by phosphatidylinositol 3-phosphates (PI(3)Ps) in vitro, and is effected via its C-terminal phospho-binding BRCTs. Consistently, mutational inactivation of 53BP1 BRCTs not only compromised PI(3)P binding, but also suppressed its ability to undergo optodroplet formation in vivo. We further show that swift 53BP1 oligomerisation following DNA damage precedes its stable assembly on DSB-flanking chromatin, requires its BRCT domain, and is suppressed by sequestration of nuclear PI(3)Ps. Taken together, we propose that PI(3)P binding underlies maturation of 53BP1 higher-order assembly on the damaged chromatin.

ABSTRACT/SUMMARYThe transition from mitosis to meiosis represents a fundamental cell-fate decision that requires coordinated remodeling of transcriptional and metabolic programs. While key transcriptional regulators of meiotic entry have been defined, how metabolic flux directly governs this process remains unclear. Here, we identify a monocarboxylate transporter1 (MCT1)-dependent metabolic checkpoint that controls meiotic progression in mammalian spermatogenesis. Through integrative single-cell transcriptomics, metabolic profiling, and computational perturbation modeling, we show that Stra8-driven meiotic initiation is coupled to a metabolic switch favoring monocarboxylic acid metabolism, prominently involving MCT1 (encoded by Slc16a1). Germ cell-specific deletion of Slc16a1 results in a complete arrest at the pachytene stage, characterized by defective homologous recombination, persistent DNA damage, and failure to activate the meiotic transcriptional program. Multi-omic analyses reveal that loss of MCT1 induces a metabolic stress-like state, suppresses expression of key meiotic regulators, and disrupts progression through the pachytene checkpoint. Mechanistically, we demonstrate that MCT1-mediated lactate influx drives histone H4 lysine 12 lactylation (H4K12la) at promoters of meiotic genes, thereby epigenetically licensing their expression. In the absence of MCT1, H4K12la deposition is lost at meiotic loci and redistributed toward stress-response pathways. Together, our findings suggest MCT1-mediated metabolism as an instructive signal that integrates metabolic state with epigenetic regulation to govern meiotic cell-fate progression, defining a previously unrecognized metabolic checkpoint at pachytene.

Acentrosomal microtubule (MT) organization is essential in many differentiated cells, yet the mechanisms that generate and maintain these networks remain poorly understood. Here, we identify Wdr62 as a conserved regulator of acentrosomal MT organization during Drosophila oogenesis. Wdr62 localizes to cortical non-centrosomal microtubule-organizing centers (ncMTOCs) and is required for proper localization of the conserved components Shot and Patronin. Loss of Wdr62 disrupts MT organization and oocyte polarity and reduces MT growth events during mid-oogenesis. Genetic analyses further reveal that Wdr62 functionally cooperates with Patronin and the MT-severing enzyme Katanin 80 to organize the acentrosomal MT network. Our data support a model in which Wdr62 promotes stabilization of MT minus ends through Patronin while Katanin-mediated severing generates new MT seeds that amplify the MT network. Moreover, Wdr62 and Patronin function together during assembly of the acentrosomal meiotic spindle, and their loss compromises fertility. Given that WDR62 mutations are associated with human disease in cell types that rely on acentrosomal MT organization, such as neurons, these findings provide insight into how disruption of WDR62-dependent MT organization may contribute to disease beyond female infertility.

Germline pathogenic variants in BRCA1 and BRCA2 confer disproportionately elevated cancer risks in breast and ovarian tissues, yet the basis for this tissue specificity remains incompletely understood. Here, we integrate bulk-tumor aneuploidy analysis across 340,824 cancer cases from three independent cohorts (TCGA, ICGC PCAWG, and FoundationCore) with single-cell whole-genome sequencing from two independent studies to investigate whether tissue-specific patterns of chromosomal deletion contribute to this phenomenon. We find that breast and ovarian cancers are consistently enriched for deletions of chromosome arms 17q and 13q--harboring the BRCA1 and BRCA2 genes, respectively--relative to other solid tumor types, and that mutational timing analysis independently places these deletions among the earliest somatic events in these cancers. Phylogenetic reconstruction of single-cell data reveals that in pre-malignant breast tissue from germline BRCA1/2 carriers, chr17q and chr13q deletions appear as localized subclonal events within small clades against a largely diploid background. In established malignancies, these same deletions are found within dominant clonal lineages accompanied by widespread genomic instability--consistent with clonal sweeps originating from early deletion events. These findings suggest that breast and ovarian cellular environments confer a selective advantage for chr17q and chr13q deletions, providing a mechanism that may contribute to the tissue-specific cancer risk observed in gBRCA1/2 carriers.

Circadian clocks impose temporal architecture on signaling networks, and disruption of this architecture predisposes to cancer metastasis. Through direct pharmacological and genetic perturbation of core clock components, we establish that circadian desynchronization in mouse lung fibroblasts eliminates temporal migration gating, creating constitutive motility responses to TNF- and TGF-{beta}, and identify YAP/TEAD as the obligate, non-redundant convergence node through which clock-regulated ECM mechanical signals and cytokine-driven transcriptional programs jointly drive cellular motility. Chronic jet lag (CJL) in mice generates nocturnal TNF- elevation (ZT12-21) that drives sustained matrix metalloprotease expression while simultaneously reorganizing Hippo and TGF-{beta} signaling toward temporal convergence during daytime hours, enabling YAP/TEAD-dependent transcription to synergize with TGF-{beta} signaling and drive epithelial-to-mesenchymal transition (EMT) programs that normally remain temporally restricted. Functional validation demonstrates CJL doubles metastatic colonization incidence (40% to 90%) following B16F10 melanoma inoculation. Critically, established metastases amplify these molecular changes: metastatic burden under CJL creates maximal TGF-{beta} expression (ZT15-21), constitutive YAP activity, and sustained EMT marker expression, while eliminating M1/M2 macrophage temporal organization. Analysis of TCGA-SKCM metastatic melanoma datasets confirms that clock-disrupted human tumors exhibit selective strengthening of YAP/TAZ, EMT, and inflammatory pathway coupling, establishing that this convergence architecture is conserved in human disease. Together, these findings demonstrate that circadian disruption transforms from a facilitator of initial metastatic colonization into a driver of progressive metastatic burden by eliminating the temporal segregation that normally constrains pro-metastatic programs to discrete, non-overlapping windows, creating self-perpetuating cycles wherein pathway convergence facilitates colonization and established tumors amplify pro-metastatic signaling to maintain permissive microenvironmental conditions.

The transcription factor p63 is critical for epithelial development and implicated in tumorigenesis. However, our understanding of the role of p63 in development and disease has been complicated by its diverse isoforms. As a member of the p53 family member of genes, TP63 encodes for numerous isoforms, including the N-terminal variants TAp63 and {Delta}Np63, which are generated through alternative promoter usage. TAp63 and {Delta}Np63 share various structural domains, including the DNA-binding domain, and primarily differ in their N-terminus which consists of intrinsically disordered regions (IDRs). The isoforms are known to have different functions, including tumor suppression in the case of TAp63 and pro-tumor formation for {Delta}Np63, but how the N-terminus contributes to isoform-specific gene regulatory effects has yet to be elucidated. Using both genomic and TurboID proximity-labeling proteomic approaches, we show that the N-terminus mediates differential interactions with cofactors that have direct effects on isoform function, specifically the regulation of apoptosis. We find that the N-terminus of TAp63 interacts with more transcriptional machinery, leading to stronger transcriptional activity by TAp63 than {Delta}Np63. However, {Delta}Np63 maintains interactions with coactivators, suggesting it can retain some transactivation capabilities. Strikingly, the N-terminus of TAp63 displays enriched interactions with chromatin modifiers, including the histone acetyltransferase KAT2A, that result in TAp63-specific binding at inaccessible sites. We find that an IDR-mediated interaction with KAT2A is involved in regulation of apoptosis by TAp63. Collectively, our results suggest a model in which TAp63 and {Delta}Np63 broadly share genomic occupancy, but differential interactions with cofactors contribute to isoform-specific regulation by TAp63 and {Delta}Np63.

Aging is a major risk factor for joint disease, yet the impact of physiological aging on the synovium remains poorly defined. Here we generate a single-cell atlas of murine ankle synovium across age and identify the sublining stromal-myeloid niche as a major site of age-associated remodeling. Aging shifted fibroblast states toward oxidative stress and matrix-remodeling programs, accompanied by sublining collagen accumulation, reduced cellularity, and loss of THY1+ sublining fibroblasts. In parallel, resident synovial macrophages exhibited altered inflammatory and phagocytic responses together with a preferential decline in TIM4+VSIG4- sublining macrophages, without overt local myeloid expansion despite systemic inflammaging. Macrophage depletion experiments further supported a link between sublining macrophages and extracellular matrix homeostasis. Together, these findings provide a reference framework for synovial aging and uncover niche-specific stromal and macrophage alterations associated with aging.