Cell Death Discovery

Despite continuous progress in diagnosis and therapy, breast carcinoma (BC) remains a major health problem. Triple-negative (Estrogen Receptor-/Progesterone Receptor-/HER2-) breast cancer (TNBC) is the most aggressive subtype due to its high metastatic potential and resistance to chemotherapy. The Y-box binding protein 1 (YB-1) transcription factor, a protein present in both cytoplasm and nucleus, is a driver of TNBC malignancy as it stimulates its cancer stem cell phenotype and disrupts cell cycle progression. Here, we hypothesized that YB-1-containing sEVs deliver YB-1 to the nuclear compartment of recipient cancer cells and play a major role in the activation of the metastatic process. We found a selective enrichment of YB-1 in sEVs from MDA and 4T1 cells, with [~]65% and 50% of all sEVs positive for YB-1 by d-STORM. Administration of sEVs from wild-type MDA and 4T1 to their YB-1 knockout counterparts resulted in nuclear translocation of sEV-associated YB-1 and increased tumorsphere formation. Pharmacological blockade of the nuclear transport machinery based on the inhibition of the formation of the "VOR" complex (VAP-A-ORP3-Rab7) by PRR851 impaired both nuclear translocation and the YB-1-induced increase in tumorsphere formation. YB-1 phosphorylation at S102 was required for nuclear localization. In fact, loss of YB-1 phosphorylation inhibited tumorsphere growth and stemness of cancer cells and YB-1-positive sEVs restored the oncogenic behavior of cancer cells expressing phospho-mutant YB-1. Moreover, PRR851 inhibited the nuclear translocation of the phosphorylated form of YB-1 and the oncogenic behavior of the TNBC cells. These data support the conclusion that the nuclear translocation of sEV-associated phosphorylated YB-1 is an important factor in the malignant behavior of TNBC and a potential therapeutic target.

Analyses of human breast carcinomas (BCs) and premalignant breast lesions show that the loss of RASSF1A is an early event in the development of ER+ BCs, which correlates linearly with malignant progression. This observation suggests that RASSF1A inhibition is important for the development and progression of ER+ BCs. In addition to RASSF1A, concurrent caveolin-1 (Cav-1) inhibition may further promote ER+ breast carcinogenesis. In the present study, transgenic Rassf1a-/- and Cav-1(-/-) single as well as Rassf1a-/-, Cav-1(-/-) double knockout mice were used to investigate the impact of single or combined Rassf1a and Cav-1 inactivation on BC initiation. Loss of either one or both proteins led to different, pre-malignant histopathological alterations within the mammary glands of the mice, but not to fully developed BC, confirming that Rassf1a and Cav-1 are both important for maintaining the integrity of mammary gland epithelial structure, but suggesting that further intracellular changes or extracellular factors are required for the development of luminal BC when both genes are lost.

The endoplasmic reticulum (ER) and its muscle-specialized form, the sarcoplasmic reticulum (SR), are crucial organelles in muscle cells, involved notably in protein synthesis, calcium regulation and muscle contraction. A well-known process involved in ER remodeling and homeostasis is ER-phagy, also called reticulophagy, a selective form of autophagic process in which ER-phagy receptors mediate the delivery of ER portions to lysosomes for degradation. SH3KBP1 is an adaptor protein involved in membrane trafficking. Recently, it was shown to control ER morphology and SR formation in striated skeletal muscle. In this study, we demonstrate that SH3KBP1 can bind to LC3B and CKAP4 proteins, bridging ER to autophagosome membranes, and is degraded by autophagy, in developing muscle fibers. Moreover, SH3KBP1 down-regulation impacts basal autophagy efficiency and ER-phagy stimulation; it also impairs the turnover of numerous ER-resident proteins. Our work highlights a new role for SH3KBP1 as a soluble ER-phagy receptor in striated skeletal muscle.

Internal-tandem-duplication of the receptor tyrosine kinase FLT3 (FLT3-ITD) generates ligand-independent signaling and is highly recurrent in acute myeloid leukemias (AMLs). One way signaling pathways can quickly influence cell fates is by phosphorylating key fate-determining proteins to trigger their proteolysis. We investigated the master transcription factor (MTF) driver of granulo-monocytic lineage-fates, CEBPA, for regulation by this mechanism because we found high CEBPA mRNA but little CEBPA protein in FLT3-ITD versus FLT3-wildtype AML cells, and inhibiting FLT3-ITD signaling with tyrosine kinase inhibitors (TKI) rapidly rescued CEBPA protein. Mass spectrometry analyses of CEBPA and its interactome demonstrated prominent interactions with major ubiquitin-proteosome pathway (UPP) components UHRF1 and USP7. TKI treatments decreased CEBPA and USP7 phosphorylations at serine 21 and serine 18 respectively alongside shifts in CEBPA interactions from degradative ubiquitin-ligase UHRF1 toward protective deubiquitinase USP7. The rescued CEBPA activated granulocytic-differentiation. Supporting that the serine-phosphorylations were phospho-degrons, UPP-inhibitors (bortezomib, MG132) increased phosphorylated and total CEBPA and USP7. The MTF regulator of apoptosis p53 is a known USP7 client, therefore, we also evaluated p53 status: TKIs and UPP-inhibitors stabilized USP7 and p53, triggering apoptosis in addition to granulocytic-differentiation specifically in FLT3-ITD but not FLT3-wildtype AML cells. UPP-inhibitors produced these consequences in TKI-resistant FLT3-ITD AML cells also. These data predicted genetic loss-of-function to CEBPA or TP53 is redundant in the FLT3-ITD context, borne out by mutual exclusivity of the mutations in clinical series. In summary, FLT3-ITD signals for CEBPA and p53 proteolysis to block lineage-maturation and apoptosis, positioning UPP-inhibitors as therapeutic candidates acting downstream of TKIs. KEY POINTSO_LIThe oncoprotein kinase FLT3-ITD signals for CEBPA and p53 proteolysis and hence suppresses lineage-differentiation and apoptosis C_LIO_LIProteosome-inhibitors are candidate remedies to restore CEBPA and p53, acting downstream of presently used FLT3-ITD kinase inhibitors C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=171 SRC="FIGDIR/small/738455v1_ufig1.gif" ALT="Figure 1"> View larger version (56K): org.highwire.dtl.DTLVardef@6ae211org.highwire.dtl.DTLVardef@12003bforg.highwire.dtl.DTLVardef@d62eb9org.highwire.dtl.DTLVardef@1958693_HPS_FORMAT_FIGEXP M_FIG C_FIG

Retinopathy of prematurity (ROP) is caused by hyperoxic exposure of prematurely born infants. The mouse model of oxygen-induced retinopathy (OIR) recapitulates pathological features of both phase I and phase II ROP. We here looked at the retinal proteins that change in response to hyperoxia in phase I of the mouse model of OIR. Using tandem mass tag labeled proteomics, we found several differentially expressed proteins (DEPs) in phase I of OIR. Of all the DEPs, we investigated the role of previously unknown protein NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 4-like 2 (NDUFA4L2). NDUFA4L2 protein and its paralog NDUFA4 are both mitochondrial complex I proteins; however, here we demonstrate that NDUFA4L2 changes in both phases of OIR, with no changes in its paralog NDUFA4, implying its unique function in pathophysiology of the disease. We demonstrate that NDUFA4L2 is an oxygen-sensitive protein and regulates retinal endothelial cell migration by rescuing isocitrate dehydrogenase flux impaired by hyperoxia in phase I of OIR.

Breast cancer is a heterogeneous disease whose clinical management relies heavily on accurate molecular subtyping. The murine E0771 mammary carcinoma cell line is widely used in preclinical studies, yet its molecular identity remains controversial, with reports variably classifying it as luminal B or triple-negative. In this study, we performed an integrated molecular and functional characterization of two independently sourced E0771 cell line stocks to resolve this discrepancy. Both stocks were genetically authenticated and exhibited concordant phenotypes. Immunohistochemical and molecular analyses demonstrated absence of oestrogen and progesterone receptors, classifying E0771 as triple-negative. Functionally, E0771 cells showed no transcriptional response to oestrogen and displayed resistance to endocrine therapy both in vitro and in vivo. Collectively, our results establish E0771 as an oestrogen-independent, basal-like triple-negative breast cancer model, supporting its appropriate use in studies of hormone-resistant breast cancer biology.

Efferocytosis, the recognition, engulfment, and degradation of apoptotic cells by phagocytes, is essential for tissue homeostasis and development, and its failure contributes to chronic inflammation and neurodegeneration. The amyloid precursor protein (APP), a central pathogenic factor in Alzheimers disease, retains physiological functions independent of amyloid production that remain poorly understood. Here, we identify a conserved, non-amyloidogenic role for APP in regulating apoptotic cell degradation via the endolysosomal pathway. Using Drosophila APPL as a model, structure-function analysis demonstrated that the intracellular internalization domain of APPL, but not its secreted ectodomain, is required for efficient apoptotic cell degradation. Immunoprecipitation coupled with mass spectrometry revealed a physical interaction between APPL and the microtubule severing ATPase Spastin, mediated by the microtubule-interacting and trafficking domain of Spastin. APPL interacts with Spastin on endosomal microtubules and modulates the dynamics of the Spastin-ESCRT-III complex, enabling Spastin to sever microtubules and promote endosomal tubule fission. Loss of APPL disrupts this process, causing aberrant endosomal tubulation and impaired lysosome biogenesis. Furthermore, it compromises the function of residual lysosomes, characterized by reduced acidity, diminished proteolytic activity, and increased lysosomal damage, which ultimately impairs the degradation of engulfed apoptotic cells. Critically, this phenotype is evolutionarily conserved in C. elegans and mice. Together, these findings establish a conserved APP-Spastin axis that regulates endolysosomal homeostasis and apoptotic cargo digestion. This reveals a critical non-amyloidogenic function of APP in maintaining tissue homeostasis through efficient efferocytosis, with broad implications for inflammatory and neurodegenerative disorders that warrant further investigation.

Stem cells proliferate rapidly to maintain fast tissue turnover during regeneration. However, the feedback mechanisms in stem cells that prevent hyperproliferation remain unclear, and their dysregulation can lead to organ failure and cancer. Here, we identified nuclear factor-Y (NF-Y) as the transcriptional repressors to maintain the stem cell quiescence during intestinal homeostasis. We found that NF-Y negatively regulates intestinal stem cell (ISC) proliferation through preferentially occupying the promoters of EGFR signaling pathway components Egfr/Mkp3/Raf/Ras/pointed, via the action of histone acetyltransferase Nejire (Nej)/p300 dependent transcription regulation. While the loss of NF-Y enhances ISC proliferation, cell death and sensitivity to stress and tumor induced mortality. Moreover, NF-Y acts together with Nej to restrict Egfr expression and suppress ISC hyperproliferation. Together, these results demonstrate NF-Y acts with Nej serve as a key negative feedback module to orchestrate transcription initiation and termination of growth signaling in the control of stem cell activity in homeostatic and disease conditions.

Necroptosis is best known as a lytic, proinflammatory cell-death pathway mediated by RIPK3 and MLKL. Effective wound repair requires the rapid resolution of inflammation, and ongoing necroptotic activity would only exacerbate tissue damage, delaying healing. However, damaged skin presents a trigger-rich environment for necroptotic signalling, an apparent paradox that remains unresolved. Using genetic ablation and pharmacological inhibition across multiple wound models, we show that inhibiting necroptosis accelerates wound closure, revealing that necroptotic signalling normally restrains repair. Surprisingly, we found that MLKL activation in wild-type keratinocytes induces differentiation and membrane repair rather than cell lysis. This adaptive, non-lethal mode of necroptotic signalling preserves barrier integrity but slows re-epithelialisation. Our findings redefine epidermal necroptotic signalling as a stress-responsive program that modulates keratinocyte fate in a trigger-rich environment. Temporarily dampening this pathway may enhance regeneration after barrier loss without compromising immune defence, revealing necroptosis as a tunable mechanism balancing tissue repair and inflammation.

Extensive experiments document that SPARCL1, a secreted protein that is produced primarily by astrocytes in brain and endothelia throughout the body and that is also known as Hevin, enhances synapse formation. However, the mode of action of SPARCL1 at synapses remains unclear owing to divergent results in the literature. Here, we use cultured neurons from newborn male and female mouse embryos to show that the C-terminal follistatin-like and Ca2+-binding domains of SPARCL1, which account for only 35% of the total SPARCL1 sequence, are sufficient to potently enhance synapse numbers. SPARCL1 acts at nanomolar concentrations at which SPARCL1 does not robustly bind to neurexins, neuroligins or neurexin/neuroligin complexes but avidly interacts with all teneurins. Strikingly, the follistatin-like domain of SPARCL1 on its own strongly binds to teneurins but is unable to stimulate synapse formation. Only when combined with the SPARCL1 Ca2+- binding domain does the follistatin-like domain induce synapses, suggesting that SPARCL1 enhances synapse numbers by binding to teneurins via its C-terminal follistatin-like domain and by activating synapse formation via its Ca2+-binding domain. SIGNIFICANCE STATEMENTSPARCL1 (also known as Hevin) is a synaptogenic factor that is produced primarily by astrocytes in brain, and that enhances synapse formation. How SPARCL1 acts at synapses, however, remains unclear because divergent results describe its binding partners at synapses and the sequences involved in its synaptogenic activity remain unclear. In the present study, we show that SPARCL1 avidly binds to the presynaptic teneurins adhesion molecules, that this binding is mediated by its small follistatin-like domain, and that its synaptogenic activity requires both its follistatin-like and its Ca2+-binding EC domains. Thus, our results suggest that SPARCL1 is recruited to developing synapses by binding of its follistatin-like domain to teneurins and then induces synapse assembly via its Ca2+-binding domain.

RNA-binding protein LARP4 plays an important role in T cell activation and differentiation, but its role in B cell biology and the pathogenesis of systemic lupus erythematosus (SLE) remains unclear. This study found that LARP4 was specifically highly expressed in B cells of SLE patients and was positively correlated with disease activity. By constructing T cell-specific and B cell-specific conditional knockout mice, we found that deletion of LARP4 in B cells, but not in T cells, significantly alleviated pristane-induced and Bm12-induced lupus nephritis. Further analysis showed that LARP4 deletion selectively inhibited B cell differentiation into plasma cells, but did not affect germinal center B cell formation. Integrated transcriptomic and metabolomics analyses revealed that this effect is due to reduced phosphatidic acid synthesis and decreased mTORC1 activity caused by mitochondrial oxidative phosphorylation dysfunction. Furthermore, we used LIPEP, a LARP4 inhibitory peptide that effectively mimicked the therapeutic effects of LARP4 gene knockout in the MRL/lpr spontaneous lupus model and outperformed cyclophosphamide in reducing glomerular immune complex deposition and improving extrarenal dermatitis. These results indicates that LARP4 is a key metabolic checkpoint regulating B cell differentiation into Plasma cells and suggest that it may be a potential therapeutic target for SLE.

Bipolar androgen therapy (BAT) exploits the paradoxical vulnerability of castration-resistant prostate cancer (CRPC) cells to rapid cycling between castrate and supraphysiologic androgen concentrations, but clinical BAT uses testosterone, which can also activate wild-type androgen receptor (AR) in androgen-responsive tissues, causing systemic side effects. 5{beta}-dihydrotestosterone (5{beta}-DHT) is a naturally occurring testosterone metabolite generally considered androgenically inactive because it binds wild-type AR weakly, yet its activity against clinically relevant AR mutants has not been systematically evaluated. Here, we tested whether 5{beta}-DHT and related 5{beta}-reduced testosterone metabolites activate AR signaling and growth programs in prostate cancer models that carry AR mutations. In C4-2 cells, 5{beta}-DHT and 3{beta}-etiocholanediol (3{beta}-ecdiol) increased canonical AR target genes, including KLK3 and TMPRSS2, with weaker activity than testosterone, whereas other 5{beta} metabolites showed limited activity. In androgen-responsive LNCaP and C4-2 models, 5{beta}-DHT and 3{beta}-ecdiol promoted cell growth under androgen-depleted conditions, and this effect was suppressed by enzalutamide, supporting AR dependence. RNA-seq confirmed that 5{beta}-DHT and 3{beta}-ecdiol induced androgen-response gene sets substantially overlapping with testosterone, albeit at lower transcriptional magnitude. Further, we found that 5{beta}-DHT, but not 3{beta}-ecdiol, suppresses cell proliferation of LNCaP, C4-2, and PC-3 cells stably expressing the clinically relevant AR gain-of-function mutants W742C and H875Y through activating AR-induced senescence-like features after high-dose exposure, consistent with the therapeutic logic of BAT. These findings identify 5{beta}-DHT as an overlooked mutant-AR agonist capable of BAT-like tumor suppression and propose it as a testosterone surrogate in BAT with potentially reduced systemic androgenic side effects. HighlightsO_LI5{beta}-DHT and 3{beta}-ecdiol promote AR-dependent prostate cancer cell growth C_LIO_LIBoth are weaker AR agonists than testosterone by RNA-seq and qPCR C_LIO_LISupraphysiologic 5{beta}-DHT suppresses growth via AR-mediated senescence C_LIO_LIGrowth suppression extends to AR mutants W742C and H875Y C_LIO_LI5{beta}-DHT may be a lower-androgenicity testosterone surrogate for BAT C_LI

WNT11, a non-canonical WNT ligand, plays well-defined roles in development and tissue architecture; however, its function in cancer remains ambiguous. Here, we characterize WNT11 as a context-dependent suppressor of cancer stemness, invasion, and in vivo tumor formation in human epithelial cancer models. We show that WNT11 upregulation reduces the expression of stemness-promoting genes, suppresses epithelial-to-mesenchymal transition, and inhibits sphere formation and tumor growth. Conversely, downregulation of WNT11 enhances these aggressive malignant properties of cancer cells. Mechanistically, we found that the ability of WNT11 to inhibit RAC1 GTPase activation is essential for its regulation of invasion and self-renewal. In cells unresponsive to WNT11, the connectivity between WNT11 and RAC1 activity is disengaged. Direct manipulation of RAC1 activity in these cells recapitulates the phenotype and molecular signature of WNT11-responsive cells, establishing RAC1 as a critical effector of WNT11-mediated tumor suppression. Taken together, these findings identify the cellular context in which WNT11 suppresses RAC1 activation as a key determinant of its anti-tumor effects and provide a mechanistic framework for understanding the diverse, and sometimes opposing, roles of WNT11 reported in cancer.

How tissue-resident T cells are organized to provide immune surveillance in healthy peripheral tissues and how this organization changes with age remains largely unknown. Here we use intravital imaging in zebrafish to identify a previously undescribed, appendage-specific mode of adaptive immune organization: fin-resident T cells undergo coordinated collective "streaming" migration within connective tissue compartments. T cells colonize the developing fin prior to lymphatic or blood vessel formation, indicating that initial residency can be established independently of classical immune conduits. However, collective streaming is not immediate; it emerges during juvenile maturation, coincident with maturation of fin architecture, and is restricted to T cells rather than other leukocyte populations. After fin amputation, young adults restore streaming within regenerated tissue once spatial compartments are re-established, whereas middle-aged fish following thymic involution repopulate the fin yet fail to promptly recover coordinated streaming and show broader tissue dispersion and altered motility in comparable times. Transcriptomic profiling across ages, regenerative states, and immune-altered microenvironments reveals coupled regulation of stromal remodeling programs and antigen presentation pathways, including differential expression of MHC class I and II components with strong microenvironmental dependence. These data define an age-regulated, tissue-instructed program that organizes resident T cell dynamics and immune potential in situ, providing a framework for understanding how tissue specific stromal environments constrain immune surveillance. Significance StatementT cells patrol most organs, but we know surprisingly little about how they are arranged inside healthy tissues over an animals lifetime. By imaging zebrafish in vivo, we discovered that fin-resident T cells do not move independently: they organize into coordinated "streams" that migrate collectively through fin connective tissue. This collective behavior appears during juvenile maturation, re-forms after regeneration in young adults, and is delayed or disrupted in older fish as age-related thymus decline reduces new T cell production. In parallel, aging and the tissue microenvironment reshape the expression of genes involved in antigen presentation. These results reveal a tissue-specific, age-regulated architecture for adaptive immune surveillance that links aging to impaired immune organization during regeneration.

Background. Post acute sequelae of COVID 19 (PASC) is clinically heterogeneous and mechanistically unresolved, and single-analyte studies have struggled to explain it. Methods. We profiled matched plasma proteomics, metabolomics and whole-blood transcriptomics at acute infection and convalescence (mean 86 days later) in a Belgian cohort, using linear mixed models, multiomic gene-set enrichment, and a degree-matched differential-correlation approach to quantify how each node's interactions were rewired between patients who developed PASC and those who recovered; seven axis proteins were additionally quantified by multiplex immunoassay as orthogonal validation. Findings. Single omic testing yielded few FDR significant features, yet multi-omic enrichment showed sustained complement cascade involvement from acute illness to follow-up in PASC. Correlation networks re-organised topologically toward C3 and lost the immunoglobulin V gene coexpression seen in recovery. The most rewired nodes, heparin cofactor II (SERPIND1), alpha 1 antitrypsin (SERPINA1), complement factor H related 5 (CFHR5), prothrombin/thrombin (F2) and immunoglobulin V gene transcripts (notably IGLV3 21), changed in their co-expression structure rather than in abundance. In multiplex validation, acute CRP was elevated in patients who developed PASC (FDR = 0.012), whereas the directly measured abundances of the network-nominated proteins were unchanged. Interpretation. These trajectory aware, cross omic networks nominate a thrombo inflammatory axis in which complement and coagulation regulation remain dysregulated in PASC at the level of wiring rather than abundance, providing a systems framework for validation and for exploring interventions at the complement coagulation platelet interface.

Glioblastoma (GBM) is a highly lethal brain cancer with limited therapeutic durability, where the majority of patients develop recurrent or persistent disease after standard chemoradiotherapy. Meanwhile, tRNA-derived fragments (tRFs) have become increasingly relevant to cancer biology; however, their clinical relevance in GBM remains undefined. Here, we report that a specific family of tRFs, 5-tRNA halves (tiR5s) dominates the small RNA landscape of GBM patient tumors and associates with worse overall survival, post-therapeutic disease persistence, and pro-invasive proteogenomic pathways across two independent GBM patient cohorts. This association between elevated tiR5 levels and therapeutic resistance re-emerges in radiation-resistant GBM xenograft models. Our findings reveal that tiR5s are an underappreciated molecular feature of highly aggressive GBM tumors, supporting further investigation into their biological roles and prognostic utility in GBM. HighlightsO_LItiR5s are the predominant tRF family in primary GBM patient tumors C_LIO_LIElevated tiR5 expression distinguishes primary GBM tumors that develop persistent disease after first-line therapy C_LIO_LIRadiation-resistant GBM PDX models show elevated tiR5 expression C_LIO_LIElevated tiR5 expression associates with poor overall patient survival and pro-invasive molecular programs in GBM patient tumors C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/738483v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@184ddc1org.highwire.dtl.DTLVardef@1faadc2org.highwire.dtl.DTLVardef@a5ae02org.highwire.dtl.DTLVardef@1431506_HPS_FORMAT_FIGEXP M_FIG C_FIG

Microcomputed tomography (micro-CT) is a useful tool that can be utilised for 3D structural characterisation and volumetric quantification of small biological specimens. Its potential application is particularly valuable within the field of cardiac development, where phenotypic profiling at the whole organ, cell, and molecular level is often most informative within the same sample. Consequently, this study sought to develop a multimodal imaging protocol to enable 3D phenotypic characterisation of embryonic avian hearts (iodine-based contrast X-ray imaging) prior to immunohistochemistry-based cell and molecular analysis. Micro-CT parameters were tested to establish an optimal protocol for 3D analysis of embryonic cardiac specimens across multiple developmental timepoints. Optimised parameters provided reliable and reproducible 3D analysis of cardiac macrostructures. Sodium thiosulphate treatment of X-ray imaged hearts effectively reversed the iodine-based contrast stain whilst maintaining antigen availability of nuclear, membranous, and cytoplasmic targets in traditional downstream imaging studies. Together, this study demonstrates a robust and highly efficient multimodal imaging strategy to comprehensively characterise cardiac morphology in avian embryos and may serve as a versatile foundation for a broad range of bioimaging applications within the wider scientific community.

Traumatic brain injury (TBI) is one of the leading causes of emergency room visits in children under 10. Children are potentially more vulnerable to the adverse effects of TBI, given that their brains are still developing at the time of injury. Indeed, early life TBI has been linked to cognitive, social, and mood-related impairments later in life. The neuroimmune system has been implicated in adult TBI mechanisms and plays numerous key roles in brain development, making it an interesting candidate for linking pediatric TBI and prolonged behavioral alterations. Here we establish a rat model of mild pediatric TBI to investigate the relationship between early life TBI, acute responses of neuroimmune cells, and chronic behavioral dysregulation. At postnatal day 15, which is roughly equivalent to toddler age, male and female rat pups received a TBI via lateral fluid percussion injury. At 3 days post injury, TBI increased microglia and astrocyte coverage locally in the Perilesional Cortex but not in more distant corticolimbic regions. However, the hippocampus and prefrontal cortex did exhibit increased expression of the phagocytic marker CD68 in microglia, suggesting widespread glial activation even in the absence of gross coverage change. TBI also impacted mast cells, early-response innate immune cells, increasing their number and degranulation in multiple regions. In the juvenile and early adult periods, TBI impaired cognitive function, reduced sociability, and increased avoidance, with no change in anxiety-like behavior. Later in adulthood, TBI continued to impact cognitive behavior, increasing risky decision-making and impairing optimization months after injury. Together, these results suggest that pediatric TBI causes lasting cognitive and social dysregulation, possibly via acute neuroimmune alterations following injury at a critical period of brain development.

UNC-6/Netrin is a conserved regulator of dorsal-ventral axon and cell migrations. UNC-6 is composed of a Laminin N-terminal domain (LN), three epidermal growth factor repeats (EGF), and a Netrin C terminal domain (NC). Here, we identified missense mutations in distinct UNC-6 domains and assessed their roles in dorsal VD/DD motor axon guidance and ventral AVM axon guidance. A missense mutation in a conserved residue of the LN domain (G289D) resulted in dorsal and ventral axon guidance defects similar to unc-6 null. A distinct missense mutation in the LN domain (S120F) was hypomorphic and strongly perturbed ventral AVM axon guidance with minimal effects on dorsal VD/DD axon guidance, showing that S120F is predominantly required for ventral guidance. Missense mutations altering conserved cysteine residues involved in di-sulfide bonding in the EGF domains were analyzed. EGF1(C321G) caused both ventral and dorsal axon guidance defects albeit weaker than unc-6 null, indicating that EGF1 is required for both. EGF2(C347Y) strongly affected dorsal VD/DD axon guidance similar to unc-6 null, with weaker perturbation of ventral AVM axon guidance. Previous results revealed that EGF3(C410Y) specifically disrupted dorsal axon guidance, a result that we confirmed. Our studies using missense mutations in the endogenous unc-6 locus complement previous structure-function studies using transgenic expression, and identify domains specifically required for ventral AVM guidance (S120Y in the LN domain) and dorsal VD/DD axon guidance (C410Y in EGF3). The crystal structure of UNC-6 indicates conserved N-linked glycosylation at N114 and N128. Mutation of these sites in UNC-6 had no effect on dorsal ventral axon guidance, showing that they do not play a major role. However, the N114 and N128 mutations interacted genetically with unc-40 and unc-5 mutations, indicating that these glycosylation sites indeed have a role in UNC-6 signaling. Our results will inform studies on how these distinct UNC-6 domains interact with guidance receptors (e.g. UNC-40/DCC and UNC-5) and other extracellular molecules to mediate dorsal-ventral axon guidance.

Rheumatoid arthritis is a chronic inflammatory joint disease in which progressive destruction of cartilage and bone drives long-term disability. Current disease-modifying therapies target the immune and cytokine networks that sustain synovial inflammation, but none is directed at the chondrocyte, the resident cell responsible for maintaining cartilage matrix. Chondrocyte survival and matrix homeostasis depend on {beta}1-integrin-mediated adhesion to the extracellular matrix, and dysregulated integrin signalling has been implicated in cartilage injury. Here we test the hypothesis that allosteric modulation of {beta}1 integrin, rather than simple adhesion blockade, is chondroprotective. Using the monoclonal antibody JB1a, which binds an epitope in the hybrid domain of {beta}1 integrin and stabilises the receptor in a low-affinity conformation, we show that intra-articular administration produces both functional and structural amelioration of Freunds complete adjuvant (FCA)-induced arthritis in mice. JB1a abolished the FCA-induced increase in joint diameter and hyperalgesia and markedly reduced synovial inflammation, pannus formation and cartilage erosion, with no effect on the contralateral joint and no observed adverse effects. These changes were accompanied by a reduction in chondrocyte apoptosis in vivo. In primary human articular chondrocytes, JB1a abolished interleukin-1{beta} (IL-1{beta})-induced caspase 3/7 activation, reduced IL-8 secretion, and restored the sinusoidal oscillation of intracellular ATP that was otherwise abrogated by IL-1{beta}. In contrast, the adhesion-blocking, integrin-clustering antibody 6S6 activated caspase 3/7 and amplified IL-1{beta}-induced IL-8 secretion, indicating that the therapeutic effect is a property of the specific mode of receptor engagement rather than of adhesion blockade per se. These findings identify {beta}1-integrin conformational state as a determinant of chondrocyte energy homeostasis and survival, and nominate allosteric {beta}1-integrin modulation as a mechanistically distinct, chondrocyte-directed therapeutic strategy in inflammatory arthritis.