Chinmay M. Trivedi

Roberts syndrome is caused by biallelic ESCO2 pathogenic variants, but the mechanisms linking ESCO2 loss to embryonic endothelial failure remain poorly defined. Endothelial cells must maintain identity and resist endothelial-mesenchymal transition (EndMT), yet conventional transcriptomics measures gene abundance rather than isoform composition. Here, using endothelial-specific Esco2 deletion in a mouse model relevant to Roberts syndrome, we show that Esco2 loss causes yolk sac vascular remodeling failure, pathological EndMT, diversion from hemogenic endothelial fate, hemogenic endothelial depletion, impaired hematopoietic output, and embryonic lethality. Short-read single-cell RNA-seq revealed broad endothelial reprogramming, whereas single-cell long-read isoform sequencing uncovered a hidden layer of isoform dysregulation that conventional gene-level analysis failed to resolve. Esco2-deficient endothelium exhibited transcriptome-wide isoform switching, disruption of a multi-tier splicing-factor network, and predicted broad loss or rewiring of protein-coding output. Chromatin occupancy profiling localized Esco2 to exonic regions near alternatively spliced loci, supporting a cotranscriptional route to spliceopathy. Whole-genome sequencing showed that local DNA variation was insufficient to explain these changes, supporting a predominantly posttranscriptional mechanism. These findings identify isoform control as a disease-relevant layer of endothelial identity maintenance in Roberts syndrome.

Aortic valve stenosis is a progressive and increasingly prevalent disease in older adults, with no approved pharmacologic therapies to prevent or slow its progression. Although genetic risk factors have been identified, the contribution of epigenetic regulation remains poorly understood. Here, we demonstrated that histone deacetylase 3 (HDAC3) maintains aortic valve structure by suppressing mitochondrial biogenesis and preserving extracellular matrix integrity in valvular interstitial fibroblasts. Human stenotic valves displayed elevated acetylation of histone H3 at lysine 27 (H3K27ac) and reduced HDAC3 activity in diseased regions. Mice lacking HDAC3 in aortic valves developed aortic valve stenosis, disrupted collagen organization, increased H3K27ac, and premature mortality. Mechanistically, HDAC3 loss led to activation of nuclear hormone receptor-regulated mitochondrial gene programs, increased oxidative phosphorylation, and reactive oxygen species-induced damage. Treatment with metformin, a mitochondrial complex I inhibitor, restored redox balance, preserved collagen structure, and improved valve function in Hdac3-deficient mice. Supporting these experimental findings, retrospective clinical analysis revealed a significantly lower prevalence and slower progression of aortic valve stenosis in patients treated with metformin. These results uncovered a potentially previously unrecognized role for HDAC3 in coordinating epigenetic and metabolic homeostasis in the aortic valve, suggesting that targeting mitochondrial dysfunction may offer a therapeutic strategy for noncalcific aortic valve disease.

Purpose of Review This review delves into recent advancements in understanding generalized and organ-specific lymphatic development. It emphasizes the distinct characteristics and critical anomalies that can impair lymphatic function. By exploring developmental mechanisms, the review seeks to illuminate the profound impact of lymphatic malformations on overall health and disease progression. Recent Findings The introduction of genome sequencing, single-cell transcriptomic analysis, and advanced imaging technologies has significantly enhanced our ability to identify and characterize developmental defects within the lymphatic system. As a result, a wide range of lymphatic anomalies have been uncovered, spanning from congenital abnormalities present at birth to conditions that can become life-threatening in adulthood. Additionally, recent research highlights the heterogeneity of lymphatics, revealing organ-specific developmental pathways, unique molecular markers, and specialized physiological functions specific to each organ. Summary A deeper understanding of the unique characteristics of lymphatic cell populations in an organ-specific context is essential for guiding future research into lymphatic disease processes. An integrated approach to translational research could revolutionize personalized medicine, where treatments are precisely tailored to individual lymphatic profiles, enhancing effectiveness and minimizing side effects.

Over the past several centuries, the integration of contemporary medical techniques and innovative technologies, like genetic sequencing, have played a pivotal role in enhancing our comprehension of congenital vascular and lymphatic disorders. Nonetheless, the uncommon and complex characteristics of these disorders, especially considering their formation during the intrauterine stage, present significant obstacles in diagnosis and treatment. Here, we review the intricacies of these congenital abnormalities, offering an in-depth examination of key diagnostic approaches, genetic factors, and therapeutic methods.

Viral myocarditis, an inflammatory disease of the heart, causes significant morbidity and mortality. Type I interferon (IFN)-mediated antiviral responses protect against myocarditis, but the mechanisms are poorly understood. We previously identified A Disintegrin And Metalloproteinase domain 9 (ADAM9) as an important factor in viral pathogenesis. ADAM9 is implicated in a range of human diseases, including inflammatory diseases; however, its role in viral infection is unknown. Here, we demonstrate that mice lacking ADAM9 are more susceptible to encephalomyocarditis virus (EMCV)-induced death and fail to mount a characteristic type I IFN response. This defect in type I IFN induction is specific to positive-sense, single-stranded RNA (+ ssRNA) viruses and involves melanoma differentiation-associated protein 5 (MDA5)—a key receptor for +ssRNA viruses. Mechanistically, ADAM9 binds to MDA5 and promotes its oligomerization and thereby downstream mitochondrial antiviral-signaling protein (MAVS) activation in response to EMCV RNA stimulation. Our findings identify a role for ADAM9 in the innate antiviral response, specifically MDA5-mediated IFN production, which protects against virus-induced cardiac damage, and provide a potential therapeutic target for treatment of viral myocarditis.

Patients afflicted with STING gain-of-function mutations frequently present with debilitating interstitial lung disease ( ILD ) that is recapitulated in mice expressing the STING ^V154M mutation ( VM ). Prior radiation chimera studies revealed an unexpected and critical role for non-hematopoietic cells in the initiation of ILD. To identify STING-expressing non-hematopoietic cell types relevant to ILD, we generated a conditional knock-in ( CKI ) model in which expression of the VM allele was directed to hematopoietic cells, fibroblasts, epithelial cells, or endothelial cells. Only endothelial cell-targeted expression of the mutant allele resulted in the recruitment of immune cells to the lung and the formation of bronchus-associated lymphoid tissue, as seen in the parental VM strain. These findings reveal the importance of endothelial cells as instigators of STING-driven lung disease and suggest that therapeutic targeting of STING inhibitors to endothelial cells could potentially mitigate inflammation in the lungs of SAVI patients or patients afflicted with other ILD-related disorders. Summary: Patients with STING gain-of-function (GOF) mutations develop life-threatening lung autoinflammation. In this study, Gao et al. utilize a mouse model of conditional STING GOF to demonstrate a role for endothelial STING GOF in initiating immune cell recruitment into lung tissues of SAVI mice.

Adaptive thermogenesis by brown adipose tissue (BAT) dissipates calories as heat, making it an attractive anti-obesity target. Yet how BAT contributes to circulating metabolite exchange remains unclear. Here, we quantified metabolite exchange in BAT and skeletal muscle by arteriovenous metabolomics during cold exposure in fed male mice. This identified unexpected metabolites consumed, released and shared between organs. Quantitative analysis of tissue fluxes showed that glucose and lactate provide ~85% of carbon for adaptive thermogenesis and that cold and CL316,243 trigger markedly divergent fuel utilization profiles. In cold adaptation, BAT also dramatically increases nitrogen uptake by net consuming amino acids, except glutamine. Isotope tracing and functional studies suggest glutamine catabolism concurrent with synthesis via glutamine synthetase, which avoids ammonia buildup and boosts fuel oxidation. These data underscore the ability of BAT to function as a glucose and amino acid sink and provide a quantitative and comprehensive landscape of BAT fuel utilization to guide translational studies.