Defective endometrial decidualization is one major cause of female infertility, yet the underlying mechanisms remain elusive. Here, we identified that protein arginine methyltransferase 5 (PRMT5) which was upregulated during decidualization and by progesterone stimulation, is markedly down-regulated in the endometria of patients with recurrent implantation failure (RIF), along with a global reduction of symmetric dimethylarginine (sDMA). Uterine stromal-specific ablation of Prmt5 in mouse severely impaired decidualization leading to infertility. A multi‑omics analysis in human endometrial stromal cells (EnSCs) revealed that PRMT5 promoted decidualization primarily by catalyzing sDMA at arginine 346 (R346) of the orphan nuclear receptor Nur77, which directs its proper chromatin occupancy. Targeting the PRMT5-Nur77 methylation axis, we designed a peptide, Pep‑Nur77-R346K, which rescued the decidualization of multiple preclinical models: PRMT5 deficient human EnSCs, both genetic knockout (Prmt5d/d) and pharmacologically inhibited mouse models, an estrogen deficient mouse model, and, more importantly, the primary RIF EnSCs. In a retrospective cohort of 114 participants, the correlated reductions of endometrial PRMT5/Nur77-R346me2s was confirmed, which demonstrated robust predictive value for pregnancy outcome. Our work establishes the PRMT5‑Nur77 methylation axis as a key regulator of endometrial receptivity, and highlights both a novel diagnostic biomarker and a peptide‑based therapeutic potential for fertility.

Epilepsy affects approximately 50 million people worldwide, yet more than half of individuals with a presumed genetic cause still lack a molecular diagnosis despite the identification of over 1,000 monogenic epilepsy genes. This diagnostic gap is unlikely to be resolved by improved variant detection alone, suggesting that variants affecting the same biological pathway may combine to cause disease. By studying epilepsy-associated actin regulatory genes, we identified a conserved "actin-mitochondria-glutamate (AMG) pathway". We demonstrate that reduced actin polymerization promotes DRP1-mediated mitochondrial fission, increases reactive oxygen species (ROS) levels, and enhances glutamatergic transmission, leading to seizures. The glial innate immune pathway, a recently recognized contributor to epilepsy, is activated when the AMG pathway is affected. Reducing mitochondrial fission with the DRP1 inhibitor Mdivi-1, or suppressing ROS with N-acetyl-L-cysteine amide (NACA), significantly alleviates seizures. Importantly, digenic heterozygous loss‑of‑function variants in AMG‑pathway genes combine to cause seizures, and individuals with epilepsy of unknown etiology show an increased burden of such variants when compared to the controls. Modeling patient‑specific digenic combinations in Drosophila confirms that many combinations promote seizure susceptibility. Together, these findings establish the AMG pathway as a mechanistic framework for identifying digenic etiologies in epilepsy and highlight potential therapeutic targets.

Hepatic stellate cell (HSC) activation can lead to liver fibrosis, for which there are no effective treatments. Aberrant cytoskeletal reorganization is a central driver of HSC activation. Non-muscle myosin II (NM II) is known to regulate cytoskeleton remodeling via its actin cross-linking and contractile properties. However, the molecular players controlling actomyosin assembly and contractility in HSCs during liver fibrosis remain poorly defined. Here, we identified integrin β-like 1 (ITGBL1) as a gatekeeper of HSC quiescence by negatively regulating actomyosin contractility-driven mechanotransduction in HSCs. ITGBL1 expression was markedly elevated in activated HSCs found in patient and mouse fibrotic livers. Unexpectedly, HSC-specific Itgbl1 deficiency worsened liver fibrosis, whereas ITGBL1 overexpression in HSCs limited it, suggesting a protective role for ITGBL1 against a pathogenic HSC activation. Multi-omics and functional analyses revealed that ITGBL1 impaired F-actin filament organization in HSCs by disrupting myosin heavy chain 9 (MYH9, also named NM II heavy chain A)-dependent actomyosin assembly. In line, HSC-specific Myh9 deficiency or silencing of Myh9 in HSCs alleviated liver fibrosis. Taken together, our findings unveil the ITGBL1-MYH9 interaction acts as a critical mechano-regulatory brake that maintains cytoskeletal equilibrium and mechanical homeostasis in HSCs, providing a promising therapeutic strategy to combat liver fibrosis.

Cholesterol overload contributes to metabolic dysfunction-associated steatohepatitis (MASH) progression. One major pathway that limits hepatic cholesterol accumulation is export via VLDL secretion. While sterol regulatory element-binding protein (SREBP) activity is suppressed by insulin-induced gene 1 (INSIG1) under high sterol conditions, VLDL secretion nonetheless persists to prevent lipotoxicity and liver injury, presenting an unresolved paradox in cholesterol sensing and lipoprotein export. Here, we identified a cholesterol-responsive interaction between nuclear factor erythroid 2 related factor-1 (NFE2L1) and INSIG1 that preserved cholesterol homeostasis by sustaining VLDL secretion. Liver-specific NFE2L1 deletion elevated INSIG1 abundance, suppressed SREBP1 activation, and impaired VLDL secretion, leading to hepatic cholesterol accumulation and liver injury. Mechanistically, NFE2L1 bound to INSIG1 via its N-terminal homology box 2 (NHB2) domain; free cholesterol strengthened this interaction to promote INSIG1 degradation, thereby enabling SREBP1 activation and VLDL export. In NFE2L1-deficient mice, WT NFE2L1, but not a mutant NFE2L1 form unable to interact with INSIG1 (NHB2-deleted mutant, ΔNHB2), restored SREBP1 activity and VLDL secretion. Lipidomics analysis revealed that NFE2L1 deficiency reduced serum triglyceride composition, which was restored exclusively by WT NFE2L1. In a murine MASH model, NFE2L1 overexpression activated SREBP1/2, lowered hepatic cholesterol, and attenuated liver injury, inflammation, and fibrosis, without elevating atherogenic lipoproteins owing to compensatory LDL receptor upregulation. Together, these findings explain how VLDL secretion capacity was maintained under cholesterol excess and identify the NFE2L1/INSIG1 axis as a sterol-responsive safeguard for hepatic lipid homeostasis and a potential therapeutic target for MASH.

Alternative splicing is a pervasive mechanism that expands the coding potential and functional complexity of the human genome. Dysregulated isoform usage alters gene functions and contributes broadly to human disease across developmental, neurodegenerative, and cancer settings. Technologies for characterizing splicing and isoforms have advanced rapidly, evolving from Sanger sequencing of individual cDNA clones to high-throughput next-generation sequencing of splice junctions, and more recently to long-read sequencing that resolves full-length transcripts at bulk, single-cell, and spatial resolutions. With the growing recognition of their critical roles in human disease, multiple therapeutic modalities have been developed to precisely target splicing and isoform regulation at the DNA, RNA, and protein levels. Clinical-grade small molecules and antisense oligonucleotides that modulate aberrant RNA splicing and isoform switching have become available, offering new hope for previously incurable diseases. Here, we review this crucial yet underexplored layer of transcriptomic regulation in human disease, encompassing regulatory mechanisms, technological advances, therapeutic strategies, and future directions.

Members of the type 2 histone lysine methyltransferase family (KMT2s) are key drivers of enhancer activation and are the most mutated group of epigenetic regulators in different cancer types. Within this family, KMT2C and KMT2D have the highest mutational incidence across various cancers. To evaluate their role in gastric cancer, Wang et al. developed a Pten deficiency-driven genetically engineered mouse model with inducible loss of Kmt2c and Kmt2d in gastric epithelial cells. Through extensive in vitro, in vivo, and in silico analyses, the authors revealed that the concomitant loss of Kmt2c and Kmt2d promotes gastric carcinogenesis while enhancing antigen presentation and sensitivity to immunotherapy and targeted approaches like mTOR inhibition, highlighting the tumor-suppressive roles of KMT2C/D in gastric cancer and uncovering a vulnerability for this dismal condition.

Metabolic dysfunction-associated steatohepatitis (MASH) affects 1.5%-6.5% of the global population, yet its mechanisms remain incompletely understood. Cholesterol overload is a key driver of MASH, suggesting that targeting cholesterol sensing may offer therapeutic benefits. In this issue, Deng et al. identified nuclear factor erythroid 2-related factor 1 (NFE2L1) as a critical regulator linking cholesterol sensing to VLDL-mediated lipid export. Mechanistically, NFE2L1 interacts with insulin-induced gene 1 (INSIG1) and promotes its degradation in hepatocytes. This cholesterol-dependent NFE2L1-INSIG1 interaction sustains SREBP activation and VLDL secretion to maintain hepatic and systemic lipid homeostasis. Moreover, the study by Deng et al. indicates that hepatic NFE2L1 overexpression decreases INSIG1 abundance and ameliorates MASH progression, highlighting its therapeutic potential.

Oral antibiotics can predispose to joint inflammation, but this phenomenon remains poorly understood. Here, we leverage mouse models of alphavirus-induced arthritis to investigate the roles of gut commensals, metabolites, and host immune mechanisms in promoting musculoskeletal inflammation. Mice treated with a short course of oral antibiotics exhibited worsened arthritis after chikungunya (CHIKV) or Mayaro virus infections. This phenotype was associated with loss of short-chain fatty acids (SCFAs), greater intestinal permeability, and activation of gut-associated immune cells and required TLR4 signaling, MyD88 expression, monocytes, antigen-specific and bystander CD4+ T cells, and proinflammatory cytokines. Administration of exogenous SCFAs or colonization of mice with bacterial species that generate SCFAs mitigated CHIKV-induced joint inflammation. scRNA-seq revealed that gut-derived SCFAs ameliorate the inflammatory phenotype of synovial CD4+ T cells, infiltrating monocytes, and resident osteoclast-like cells. Thus, antibiotic-triggered gut dysbiosis exacerbates alphavirus arthritis by shaping the inflammatory profile of both infiltrating and resident immune cells in joint tissues.

Cholesterol biosynthesis is indispensable for CNS development and function. The developing brain relies almost entirely on intrinsic sterol synthesis to support membrane biogenesis, axonal outgrowth, synaptogenesis, and myelination. Pathogenic variants in sterol biosynthetic enzymes, including DHCR7 and DHCR24, result in complex neurodevelopmental disorders such as Smith-Lemli-Opitz syndrome and desmosterolosis. In addition to cholesterol-lowering drugs (statins), some other pharmacological agents such as antipsychotics, antidepressants, and beta blockers can also inhibit cholesterol biosynthesis due to off-target effects. This inhibition produces dual pathophysiological effects: cholesterol depletion and accumulation of its precursor, 7-dehydrocholesterol, an exceptionally oxidizable molecule that spontaneously generates toxic oxysterols. Given the intense demand for cholesterol synthesis in the developing brain, prenatal exposure to sterol biosynthesis-inhibiting medications may have far-reaching effects. In this Review, we describe convergent biochemical, genetic, and epidemiologic data that implicate developmental sterol dysregulation as a modifiable risk factor for neurodevelopmental pathology and underscore the urgent need for routine sterol pathway safety assessment in drug development and prenatal pharmacotherapy.

Type 1 regulatory (Tr1) T cells are a major source of IL-10-mediated immune regulation, yet their phenotypic definition and role in human disease remain incompletely understood. In this issue of the Journal of Clinical Investigation, Nideffer et al. provide insight into human Tr1 cells during pediatric Plasmodium falciparum (Pf) infection. The authors identified Tr1 cells as a major component of the malaria-specific CD4+ T cell response, producing both IL-10 and IFN-γ. They proposed that, in this context, Tr1 cells may be better identified by CD127 downregulation combined with CXCR6 expression than by other surface markers. Importantly, Tr1 cells exhibited suppressive function and were associated with reduced symptomatic disease but also with prolonged infection. Together, these findings refine current models of Tr1 cell identity and establish a more rigorous framework for marker validation using single-cell transcriptomics while highlighting the role of Tr1 cells in balancing immunity and immunopathology during infection.

BACKGROUNDObesity and weight loss in adults have been associated with distinct metabolome and gut microbiome features, but the extent to which those associations apply to adolescent stages remain unclear.METHODSThe Pediatric Obesity Microbiome and Metabolism Study (POMMS) enrolled 220 adolescents aged 10-18 with severe obesity (OB) and 67 individuals who were healthy weight controls (HWCs). Blood, stool, and clinical measures were collected at baseline and after a 6-month obesity intervention for the OB group. Metabolomic profiling in serum using targeted quantitative mass spectrometry and microbiome profiling in stool were performed, and those features were assessed for associations with BMI, insulin resistance, and inflammation. Fecal microbiome transplants (FMT) were performed on germ-free mice using samples from both groups to assess effects on weight gain and metabolic pathways.RESULTSAdolescents with OB exhibited higher serum branched-chain amino acid (BCAA) but lower branched-chain ketoacid (BCKA) levels compared with HWC. This pattern was sex- and age-dependent and differed from adults with obesity who show elevated levels of both BCAA and BCKA. Longitudinal analysis identified metabolic and microbial features correlated with changes in health measures during the intervention. The fecal microbiomes of adolescents with OB and HWC had similar diversity but differed in membership and functional potential. FMT from both OB and HWC donors had similar effects on mouse body weight, but specific taxa were linked to weight gain in recipients of FMT.CONCLUSIONAdolescents with OB have unique metabolomic adaptations and microbiome signatures compared with their HWC counterparts and adults with OB.TRIAL REGISTRATIONClinicalTrials.gov Identifier: NCT03139877 (Observational Study) and NCT02959034 (Repository).FUNDING SUPPORTAmerican Heart Association Grants: 17SFRN33670990, 20PRE35180195; National Institute of Diabetes and Digestive and Kidney Diseases Grant: R24-DK110492.

Beyond serving as a structural organ, the skeleton undergoes continuous remodeling and functions as an endocrine organ by secreting bioactive factors that regulate the physiology of distant tissues. Indeed, the concept of a "bone-vascular axis" has long been recognized, supported by epidemiological evidence linking osteoporosis and low bone mass to increased cardiovascular morbidity and mortality. Emerging findings now extend this paradigm to the brain, suggesting that bone- and bone marrow-derived signals influence cerebrovascular structure, function, and aging. Given that cerebrovascular dysfunction is a central driver of age-related cognitive decline, dementia, and neurodegenerative diseases, understanding this "bone-cerebrovascular axis" may offer novel opportunities for prevention and intervention. Here, we outline the cellular and molecular mechanisms underlying age-associated neurovascular impairment and summarize the biology of major bone and bone marrow cell populations, with emphasis on age-related alterations in their secretome. A central focus of this Review is the emerging evidence that age-related skeletal alterations exert systemic effects on the cerebrovasculature, highlighting how bone- and bone marrow-derived factors shape neurovascular health and pathology, which may subsequently contribute to CNS aging and neurodegeneration. A deeper understanding of these systemic interactions reframes brain aging within a whole-body context and may uncover innovative biomarkers and therapeutic strategies to mitigate neurodegeneration and other age-associated disorders.

Resistance to antiangiogenics is a major challenge in cancer therapy. These agents can either normalize or exacerbate tumor vascular abnormality and hypoxia. The mechanisms of resistance remain unclear in the latter setting. By integrating data from mouse models and clinical trials, we showed that hypoxia-inducing anti-VEGF therapy upregulated programmed cell death ligand 1 (PD-L1), yet failed to sensitize tumors to PD-L1 blockade. Mechanistically, early hypoxic stress triggered epithelial osteopontin (SPP1) production, which recruited monocytes and skewed macrophages toward M2 states, suppressing T cell cytotoxicity. Pharmacological SPP1 depletion impeded the development of hypoxia, reduced M2 infiltration, restored T cell activity, and enabled synergy between antiangiogenics and anti-PD-L1. Genetic dissection - tumor-epithelial Spp1-KO grafts and bone marrow chimeras generated by lethal irradiation and reconstitution with Spp1-/- or WT hematopoietic donors - showed that myeloid SPP1 contributed only marginally compared with epithelial SPP1. These findings identified SPP1 as a central mediator of resistance to hypoxia-inducing antiangiogenics, contributed to a comprehensive model of antiangiogenic resistance, and supported SPP1-targeted strategies to personalize immunotherapy and antiangiogenic therapy according to tumor hypoxia.

Malignant cells must rapidly synthesize nucleotides to grow and proliferate. Antimetabolite chemotherapies throw a wrench in this process by administering decoy molecules resembling nucleotide precursors that cells cannot use, such as 6-mercaptopurine (6MP) and methotrexate. While this approach remains an essential tool in the treatment of lymphoblastic leukemias and B cell non-Hodgkin lymphomas, approximately 1 in 3 patients will eventually develop therapy-resistant malignancies. In this issue of the JCI, Yang et al. investigated the metabolic adaptations that enable therapy-resistant tumors to grow in the presence of these drugs. Using their previously described mouse model of MYC-driven large B cell lymphoma, they identified that increased expression of the vesicular oligopeptide and histidine transporter SLC15A3 drives dipeptide accumulation in therapy-resistant cells. In lieu of finding other ways to make more nucleotides, these adaptations force cell growth by boosting mTOR signaling. This cunning adaptation, however, is also a vulnerability that can be targeted clinically.