Faculty Bibliography

OBJECTIVES/OBJECTIVE:The gut microbiome plays a crucial role in regulating systemic immunity and has been implicated in several chronic inflammatory diseases. Intestinal expansions of Ruminococcus gnavus (RG), a dominant gut commensal, correlate with disease flares in lupus nephritis (LN), but the underlying mechanism remains unknown. METHODS:In a Pilot cohort of patients with biopsy-proven LN, subsetted by gut microbiota community, immune status was characterised using bulk-blood RNA sequencing libraries, serum levels of representative host proteins, and levels of immunoglobulin (Ig)G antibodies to the novel lipoglycan (LG) produced by pathogenic RG strains. A Validation LN cohort was evaluated for blood transcriptomic profiles and levels of anti-LG antibodies. In murine models, mechanistic hypotheses were tested after RG gut colonisation or after intraperitoneal injection with an LG preparation, with outcomes determined by transcriptomic analyses, platelet functional readouts, and tissue histology. RESULTS:In a Pilot cohort of patients with LN, RG gut expansions were associated with high-level platelet, neutrophil, and monocyte activation. Serum levels of platelet factor 4 and release of neutrophil extracellular traps (NETs) were significantly higher in patients with high serum IgG antibody against the novel RG-specific LG, a marker of in vivo immune exposure. An LN Validation cohort confirmed these correlates and showed that anti-LG antibodies serve as a surrogate for thromboinflammatory profile in this LN-associated endotype. In mice, gut colonisation with LG-producing RG strains or a single LG injection caused megakaryocytosis and platelet activation; RG colonisation with LG-producing strains induced tubulointerstitial injury with NETosis. In vivo responses to LG toxin were Toll-like receptor 2-dependent. CONCLUSIONS:Gut expansions of the RG pathobiont may contribute to autoimmune pathogenesis through the LG toxin and cause LN flares through thromboinflammatory mechanisms in this previously unrecognised LN endotype.

Animals live in a world of microbes and must distinguish pathogens from benign commensals. A new study shows how animals use enteric neurons to sense components of the bacterial cell wall and how a pathogen-derived molecule blocks this mechanism.

Postnatal maturation of the mammalian heart requires a vast increase in respiratory enzymes. The mitochondria-specific lipid cardiolipin (CL) is essential for respiratory chain integrity but has no defined function in heart maturation. Here, we determined how the two steps of CL biogenesis, de novo synthesis and acyl chain remodeling, affect the maturation of cardiac mitochondria in mice. Cardiomyocyte-restricted deletion of the CL synthase Crls1 in late gestation does not affect CL levels at birth but blocks the increase in the tissue concentration of CL observed during normal postnatal maturation. Deletion of Crls1 prevents the postnatal rise in cristae density and in the intramitochondrial concentration of respiratory proteins. This inhibits cardiac development, precipitates heart failure, and causes death by the age of 2 weeks. In contrast, ablation of CL remodeling by cardiomyocyte-restricted deletion of Tafazzin does not disrupt mitochondrial maturation or cardiac development, although it has a similar effect on the CL concentration and profoundly alters the CL species composition. Our data show that CL synthesis, but not CL remodeling, controls expression of the respiratory chain by a mechanism independent of the CL concentration.

BACKGROUND/UNASSIGNED:Alterations in microtubule dynamics have been shown to affect cardiomyocyte membrane stiffness and modulate ion channels, including the cardiac sodium channel. While conditions, such as heart failure and Duchenne muscular dystrophy, are associated with increased detyrosination of microtubules and reduced sodium current, a potential role for microtubule detyrosination in arrhythmogenic cardiomyopathy has not been explored. We here investigated the impact of microtubule detyrosination on membrane stiffness, cardiac sodium channel distribution, and function in mouse and human models of arrhythmogenic cardiomyopathy. METHODS/UNASSIGNED:-c.2013delC, and isogenic control human-induced pluripotent stem cell-derived-cardiomyocytes were incubated for 2 to 4 hours with compounds known to decrease microtubule detyrosination (parthenolide, 10 µmol/L; EpoY, 20 µmol/L) or vehicle (dimethyl sulfoxide). Immunocytochemistry, mechano-scanning ion conductance microscopy, patch-clamp analysis, and stochastic optical reconstruction microscopy were performed. RESULTS/UNASSIGNED:-c.2013delC human-induced pluripotent stem cell-derived-cardiomyocytes displayed increased microtubule detyrosination and reduced sodium current compared with isogenic control human-induced pluripotent stem cell-derived-cardiomyocytes, which were both prevented by parthenolide and EpoY. CONCLUSIONS/UNASSIGNED:Increased microtubule detyrosination secondary to loss of PKP2 impacts cardiomyocyte (dys)function beyond the desmosome, contributing to both electrical and mechanical alterations in the setting of arrhythmogenic cardiomyopathy. Our findings identify microtubule detyrosination as a novel therapeutic target in pathophysiological conditions, such as arrhythmogenic cardiomyopathy, aimed at improving both contractile and electrical function.

The small-intestinal epithelium must simultaneously enable functions that are spatially compartmentalized along the length of the organ: nutrient absorption and protection against environmental insults. Although regional differences within the intestine have been recognized for centuries, only now has a comprehensive framework emerged to define this organization at molecular, cellular and functional levels. In this Review, we highlight the epigenetic and transcriptional features of small-intestinal zonation across longitudinal and apical-basal axes, and we examine the molecular mechanisms that establish regional gene expression profiles in epithelial cells during development and that maintain these distinctions into adulthood. We integrate these molecular insights with physiological data to present a refined model of the functional landscape of nutrient absorption. Finally, we discuss gastrointestinal diseases that target specific intestinal regions, underscoring the importance of understanding local tissue environments within this highly regionalized organ.

BACKGROUND:Alterations in periarticular lipid composition are implicated in musculoskeletal diseases, yet short-term reliability of MRI-based triglyceride composition mapping in the knee is not fully established. PURPOSE/OBJECTIVE:To evaluate 1-week repeatability of proton-density fat fraction (PDFF) and triglyceride fatty-acid composition-saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA)-in periarticular knee tissues. STUDY TYPE/METHODS:Prospective. POPULATION/METHODS:). FIELD STRENGTH/SEQUENCE/UNASSIGNED:3T; 12-echo 3D spoiled gradient-echo acquisition for chemical shift-encoded fat quantification and a proton density-weighted SPACE sequence for segmentation (0.6 mm isotropic). ASSESSMENT/RESULTS:Participants underwent repeated MRI 1 week apart. Femoral and tibial bone marrow, patella, Hoffa's fat pad, prefemoral fat pad, quadriceps fat pad, posterior fat pad, and subcutaneous adipose tissue were segmented and rigidly aligned. Voxelwise spectral fitting was used to estimate PDFF and fatty acid composition, including SFA, MUFA, and PUFA components. Repeatability metrics included bias, within-subject standard deviation (wSD), within-subject coefficient of variation (wCV%), coefficient of repeatability, and intraclass correlation coefficient (ICC). STATISTICAL TESTS/METHODS:Paired t-tests assessed systematic differences (α = 0.05); ICCs used a two-way random-effects, absolute-agreement model (ICC(2,1)). RESULTS:PDFF showed lowest variability across all regions (wCV: 1.5%-5.9%; ICC: 0.33-0.96). SFA demonstrated similar stability (wCV: 2.4%-12.6%; ICC: 0.19-0.87). MUFA exhibited anatomy-dependent reliability (wCV: 4.1%-21.1%; ICC: 0.17-0.97), with highest repeatability in subcutaneous adipose tissue (ICC: 0.97) and Hoffa's fat pad (ICC: 0.85). PUFA displayed the greatest variability (wCV: 3.6%-52.8%; ICC: 0.10-0.94), with the greatest instability in periarticular fat pads. No paired comparisons were significant (all p > 0.05; range p = 0.14-0.98). Regional ordering remained consistent across sessions. DATA CONCLUSION/CONCLUSIONS:A 12-echo chemical shift-encoded MRI protocol provides repeatable PDFF and SFA measurements over 1 week. MUFA reliability varies by tissue, while PUFA remains least stable. EVIDENCE LEVEL/METHODS:2 (Prospective cohort). TECHNICAL EFFICACY STAGE/UNASSIGNED:2 (Reproducibility/feasibility evaluation).

We present MelOD (Melanoma Omics Dashboard), a free, web-based interactive platform integrating preprocessed data from 16 melanoma studies, including eight bulk transcriptomics, six single-cell RNA-seq, and two proteomics datasets. MelOD provides user-friendly visualization and analysis tools, differential expression, dimensionality reduction, clustering, correlation, and survival analysis without requiring local computational resources. Several datasets include annotations for immunotherapy response, facilitating exploration of resistance and response signatures. Built on RShiny with optimized handling of large datasets, MelOD supports real-time hypothesis generation, cross-study validation, and community dataset contributions. Freely accessible online, MelOD lowers barriers to multi-omics research in melanoma and related fields.

This study evaluates the repeatability of a 3D simultaneous