Faculty Bibliography

The Drosophila corneal lens is an apical extracellular matrix structure with a biconvex shape that enables it to focus light onto the underlying photoreceptors. Here, we investigated how this shape is influenced by the source of one of its major components, the polysaccharide chitin. Knocking down the chitin synthase Krotzkopf verkehrt strongly reduced the thickness and curvature of the corneal lens. Conversely, enhancing chitin export by overexpressing Rebuf expanded and distorted the corneal lens. We found that the cone and primary pigment cells in the center of each ommatidium produce most of the chitin, and preventing chitin synthesis by these central cells reduced corneal lens curvature. Increasing chitin export from central cells increased the thickness of the central corneal lens, while increasing export from peripheral lattice cells made the edges thicker. The wild-type biconvex shape thus results from high levels of chitin production by central cells relative to peripheral cells, indicating that localized chitin secretion is critical for normal corneal lens curvature.

Epstein-Barr virus (EBV) plays a role in the pathogenesis of a wide variety of acute and chronic diseases. Cutaneous manifestations of EBV include exanthems, chronic infections, malignancies, and small vessel vasculitides. Clinically and histologically, many of these conditions can imitate each other, making diagnosis challenging. In this report, we present a case of a child who developed Gianotti-Crosti syndrome with histopathologic features of anti-neutrophil cytoplasmic antibody (ANCA) vasculitis in the setting of acute EBV infection. Furthermore, we review the literature on EBV-induced cutaneous small vessel vasculitis and discuss pathogenic mechanisms.

BACKGROUND & AIMS/UNASSIGNED:Atherosclerotic cardiovascular disease (ASCVD) is the leading cause of death in patients with metabolic dysfunction-associated steatohepatitis (MASH). No therapy targets both diseases simultaneously, and a roadblock for discovering new treatments is the lack of animal models that recapitulate both diseases, especially in females. METHODS/UNASSIGNED:mice (n = 8-13) were fed a western diet (WD), modified choline-deficient high-fat diet (mCDHFD), or modified MASH-inducing diet (mMASHD) containing equivalent physiological levels of cholesterol. Comprehensive multiomics including metabolomics, lipidomics, and transcriptomics, alongside histopathological and biochemical analyses, were integrated to characterize concurrent MASH and atherosclerosis. Transcriptomics was validated in other mouse models and integrated with human data (n = 79). RESULTS/UNASSIGNED:0.04). Lipidomic analyses revealed dysregulated polyunsaturated fatty acid, steryl ester, and dihexosylceramide metabolism. Integration of mouse and human transcriptomes revealed similarities in metabolic and proinflammatory/proatherogenic pathways. CONCLUSION/UNASSIGNED:This sex-based multiomics analysis establishes a murine model of concurrent MASH and atherosclerosis, reveals sex-specific dietary responses, and identifies metabolic and transcriptional pathways with potential utility as biomarkers and therapeutic targets. IMPACT AND IMPLICATIONS/UNASSIGNED:mice, we found that different diets containing equivalent physiological levels of cholesterol induce sex-specific responses, with a modified choline-deficient high-fat diet effectively modeling both diseases in both sexes, while a western diet is effective only in males. Multiomics analyses identified key metabolic and inflammatory pathways linking MASH and atherosclerosis that mirror transcriptomic signatures found in humans, and highlight circulating cholesterol, CCL2, and sphinganine as potential biomarkers. These findings establish a translational model and reveal sex-specific metabolic pathways that will advance our understanding of the shared pathophysiology of MASH and atherosclerosis, and facilitate the development of dual therapeutic approaches, addressing an urgent unmet clinical need.

BACKGROUND:Pathogenic variants in plakophilin-2 (PKP2) cause arrhythmogenic cardiomyopathy (ACM) with intracellular calcium dysregulation as a major component of its arrhythmia phenotype. Recent adeno-associated viral (AAV) based Pkp2 (AAV-PKP2) gene therapy has shown promising results in a few different PKP2-associated ACM models. Fibroblast growth factor 21 (FGF21) has multiple cardioprotective effects and has recently emerged as a promising therapeutic agent for cardiovascular disease. OBJECTIVES/OBJECTIVE:To assess the efficacy and impact on calcium regulation of a novel AAV8-based FGF21 gene therapy on adult cardiac-specific, tamoxifen-activated PKP2 knockout (PKP2-cKO) mice. METHODS:Experiments were performed using a PKP2-cKO murine model. AAV8-FGF21 was delivered to adult mice by a single tail vein injection 7 days before tamoxifen-activated PKP2-cKO. Cardiac functions were monitored by echocardiography and electrocardiography. Intracellular calcium transients were investigated in acute isolated adult mouse cardiomyocytes and calcium fluorescent signals were acquired with the IonOptix system. RESULTS:Loss of PKP2 expression caused cardiac mechanical dysfunction and pro-arrhythmic phenotype in adult mouse models. AAV-mediated delivery of FGF21 mitigated the progression of biventricular structural changes, decreased the occurrence of adrenergic arrhythmias, and rescued intracellular calcium imbalance in the setting of PKP2 haploinsufficiency. In contrast, acute in vitro FGF21 treatment for 1 hour had no effect on intracellular calcium transients. CONCLUSIONS:These beneficial effects of AAV8-FGF21 on the PKP2-ACM phenotype suggest a therapeutic landscape for various targeted cardiomyopathies.

Ribosomes are central to protein synthesis in all organisms. In mammals, the ribosome functional core is highly conserved. Remarkably, two rodent species, the naked mole-rat (NMR) and tuco-tuco, display fragmented 28S ribosomal RNA (rRNA), coupled with high translational fidelity and long lifespan. The unusual ribosomal architecture in the NMR and tuco-tuco has been speculated to be linked to high translational fidelity. Here, we show, by single-particle cryo-electron microscopy, that despite the fragmentation of their rRNA, NMR and tuco-tuco ribosomes retain their core functional architecture. Compared to ribosomes of the guinea pig, a phylogenetically related rodent without 28S rRNA fragmentation, ribosomes of NMR and tuco-tuco exhibit poorly resolved density for certain expansion segments. In contrast, the structure of the guinea pig ribosome shows high similarity to the human ribosome. Enhanced translational fidelity in the NMR and tuco-tuco may stem from subtle, allosteric effects in dynamics, linked to rRNA fragmentation.

An animal's survival hinges on its ability to integrate past information to modify future behavior. The nematode Caenorhabditis elegans adapts its behavior based on prior experiences with pathogen exposure, transitioning from attraction to avoidance of the pathogen. A systematic screen for the neural circuits that integrate the information of previous pathogen exposure to modify behavior has not been feasible because of the lack of tools for neuron type-specific perturbations. We overcame this challenge using methods based on compressed sensing to efficiently determine the roles of individual neuron types in learned avoidance behavior. Our screen revealed that distinct sets of neurons drive exit from lawns of pathogenic bacteria and prevent lawn re-entry. Using calcium imaging of freely behaving animals and optogenetic perturbations, we determined the neural dynamics that regulate one key behavioral transition after infection: stalled re-entry into bacterial lawns. We find that key neuron types govern pathogen lawn-specific stalling but allow the animal to enter nonpathogenic Escherichia coli lawns. Our study shows that learned pathogen avoidance requires coordinated transitions in discrete neural circuits and reveals the modular structure of this complex adaptive behavioral response to infection.