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Geometrical preference of anchoring sites in the unicellular organism <i>Stentor coeruleus</i>

Organisms often inhabit environments comprising complex structures across various scales. Animals rely on visual information from surrounding geometrical structures for navigation. Even at the microscale, various microsediments form complex structures in microbial habitats. The movement of microorganisms is passively affected by collisions and hydrodynamic interactions with surrounding structures. However, the influence of microenvironmental geometry on behavioral changes of unicellular organisms that lack visual perception remains unclear. Here, we developed geometrically structured chambers to investigate anchoring site preferences in the swimming ciliate Stentor coeruleus . Our experiments revealed that S. coeruleus preferentially anchored in narrow regions characterized by specific geometrical features, including corner angle, depth, and curvature at the corner end. Before anchoring, free-swimming S. coeruleus changed its behavior to move along the boundary wall of the chambers, accompanied by Ca 2+ -induced asymmetrical body deformation. To further investigate how S. coeruleus moves along the wall continuously, we conducted a hydrodynamic simulation and revealed that the asymmetric morphology causes asymmetric propulsive forces, explaining wall-following behavior through physical interactions with a wall. Thus, morphological change near a wall causes wall-following behavior, facilitating the identification of these narrow anchoring sites. Our findings indicate that environmental geometry drives behavioral transitions in S. coeruleus through simple biophysical processes, enabling spatial selection without visual cues. Overall, these results suggest that microgeometry plays a key role in shaping ecological niches for unicellular microorganisms.

Natural History of Patients With Histologically Proven Acute Eosinophilic Myocarditis

BACKGROUND: No large registries of patients with acute eosinophilic myocarditis (EM) are available. However, EM is perceived as a cardiac disease with high mortality, affecting mainly young and middle-aged adults according to small series and case reports. Awareness of the clinical presentation, associated systemic conditions, treatments, and outcomes of this uncommon condition is an unmet need. METHODS: In this international, multicenter, retrospective cohort study, 53 centers screened 193 patients with histologically proven acute EM between 1992 and 2023. After the exclusion of patients with insufficient data (n=10), symptoms lasting &gt;30 days (n=19), or histological diagnosis not confirmed after review (n=8), 156 patients were included. RESULTS: Median age at presentation was 48 years (first to third quartile, 34–59 years) with male predominance (67.3%), and only 2 were pediatric cases (≤16 years of age; 1.3%). The main signs and symptoms at presentation were dyspnea (75.6%), fever (61.3%), and chest pain (53.2%). Unexpectedly, peripheral eosinophilia was reported in only 57.4% of cases, with a median cell count of 630 eosinophils/μL. The median left ventricular ejection fraction at presentation was 32% (first to third quartile, 25%–48%). The disorders most frequently associated with EM were eosinophilic granulomatosis with polyangiitis (22.4% of cases) and hypersensitivity forms (14.1%). Idiopathic/undefined forms accounted for 44.9% of cases, and miscellaneous causes accounted for 18.6%. In-hospital death or need for heart transplantation (HTx) occurred in 23 patients (14.7%; 22 deaths and 1 HTx), despite 43.6% being treated with temporary mechanical circulatory support and 92.9% being treated with immunosuppressive agents. Estimated rates of death or HTx at 1 and 3 years were 19.0% and 23.8%. Increased age, decreased left ventricular ejection fraction on admission, and no immunosuppressive therapy during hospitalization were independent predictors of death or HTx. A nonsignificant higher occurrence of deaths or HTx was observed in the hypersensitivity form (46.1%) compared with the eosinophilic granulomatosis with polyangiitis–associated form (13.1%) at 3 years ( P =0.15). CONCLUSIONS: Acute EM can often present without peripheral eosinophilia, and rates of in-hospital and midterm mortality or HTx are high. Endomyocardial biopsy is required to reach the final diagnosis of EM because relying on peripheral eosinophilia can lead to missing diagnosis. In-hospital immunosuppression is associated with HTx-free survival, although tailored immunosuppressive therapies are needed to improve outcomes. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT06447935.

Unraveling the maturation pathway of a eukaryotic virus through cryo-EM

Virus maturation is a fundamental biological process involving large-scale structural reorganizations that drive functional activation and lead to infectivity. Understanding the steps from the initial procapsid assembly to mature virions is essential, both for comprehending viral life cycles and for developing antiviral therapies. However, capturing these steps has been challenging due to the transient and elusive nature of intermediate states. The nonenveloped, T = 4, ssRNA-containing, Nudaurelia capensis omega virus (NωV) is a highly accessible model system that exemplifies the maturation process of a eukaryotic virus. During maturation, the particle shrinks in outer diameter from 482 Å (pH 7.6) to 428 Å (pH 5.0). It is possible to mimic the maturation process in vitro by lowering the pH of a population of procapsids produced in heterologous systems. Indeed, by controlling the pH in vitro, it is possible to produce homogenous populations of intermediate NωV virus-like particles (VLPs) that occur too fleetingly to be observed in vivo. Here, we report structural models, based on cryoelectron microscopy (cryo-EM), of five intermediates in the NωV maturation process. The structures of the intermediate particles reveal unique, quaternary position-dependent trajectories and refolding of subunit N and C-terminal regions, including the formation of the autocatalytic cleavage site at N570. The detailed structures reported here, coupled with previously determined structures of the procapsids and mature particles, allow the maturation pathway to be described in detail for a eukaryotic virus.

Bradycardia in Athletes: Prevalence, Mechanisms, and Risks

BACKGROUND: Sinus bradycardia is a well-recognized physiological adaptation in endurance athletes, primarily attributed to sinus node remodeling or increased vagal modulation. Although genetic influences on resting heart rate (HR) have been observed, the genetic contribution to athletic bradycardia has not been elucidated. METHODS: We phenotyped current and former elite endurance athletes in the Pro@Heart cohort study using multimodal cardiac imaging, cardiopulmonary exercise testing, and Holter monitoring. Genetic susceptibility to bradycardia was assessed using a validated HR-associated polygenic risk score (HR-PRS), in which lower scores are associated with a lower HR, and compared with healthy nonathletic controls. Clinical and genetic features of bradycardic endurance athletes with minimum HR ≤40 bpm on a Holter monitor (bradycardic athletes [BAs]) were compared with non-BAs). A healthy cohort of nonathletes from the ASPREE study (Aspirin in Reducing Events in the Elderly) were used for genetic comparisons. RESULTS: Among 465 endurance athletes (median age, 23 [18–49] years, 75% men), 175 (38%) had a minimum HR on a Holter monitor ≤40 bpm, of whom 7 (2% of total) had a HR ≤30bpm. Pauses ≥2 s were observed in 115 (25%) athletes, of whom 12 (3% of total) had pauses ≥3 s. Mobitz I second-degree atrioventricular block was observed in 15 (3% of total) athletes. BAs were younger and fitter and exhibited greater athletic cardiac remodeling than non-BAs. Mean HR-PRS was significantly lower in all athletes compared with ASPREE nonathletes ( P &lt;0.001) and in BAs compared with non-BAs ( P =0.006). When the distribution of HR-PRS within our athletic cohort was considered, athletes with scores in the bottom quartile had a lower minimum HR (median HR, 41 [35–45] bpm versus 45 [40–49] bpm, P &lt;0.001) and higher bradycardia burden (14 [2–37]% versus 2 [0%–25]%, P &lt;0.001) than those with scores in the top quartile. After adjusting for age, sex, fitness, and indexed right atrial volume, HR-PRS was independently associated with lower minimum HR and increased the odds of resting bradycardia by 2-fold (odds ratio [OR], 2.2 [95% CI, 1.3–3.9]; P= 0.004). Neither bradycardia nor pauses were associated with increased risk of adverse outcomes over 5.5 years. CONCLUSIONS: Resting bradycardia (HR ≤40 bpm) and pauses of 2 to 3 s are present in a significant proportion of endurance athletes and are well tolerated. Our data suggest that both fitness and genetic variation contribute to sinus node function in endurance athletes. Intriguingly, HR-PRS differed between athletes and nonathletes, raising the possibility that genetics may be a determinant of athleticism.

When alternative becomes essential: The role of mitochondrial glycerol-3-phosphate dehydrogenase

Complex I is known as the primary entry point for electrons within the mitochondrial electron transport system (ETS). However, the glycerol-3-phosphate (G3P) shuttle, composed of cytosolic and mitochondrial G3P dehydrogenase (cG3PDH and mtG3PDH, respectively), transfer reducing equivalents from the cytosol to the mitochondrial matrix. The mtG3PDH feeds electrons into the ETS via FADH 2 oxidation, but with theoretically lower energy conversion efficiency than complex I. It is thus believed to be an “alternative” pathway, only supporting mitochondrial respiration when complex I fails. mtG3PDH also plays an important role in reactive oxygen species (ROS) production. To investigate the role of this understudied protein in mitochondrial bioenergetics and redox homeostasis, we generated Drosophila melanogaster mutant lines for mtG3PDH (GPO1) using a CRISPR/Cas9-based approach and determined several physiological and metabolic parameters. A drastically higher mortality rate was observed among the GPO1 flies, as well as a lethargic behavior characterized by an inability to climb. These results are in accordance with an impaired mitochondrial efficiency (ATP/O) mainly due to decreased ATP production (~60% decrease) and O 2 consumption (~33% decrease), rather than elevated ROS. In fact, GPO1 flies produced ~70% less ROS than controls, likely due to the reduced direct and reverse electron transfer-related ROS production from mtG3PDH. These results support an essential role of mtG3PDH in mitochondrial bioenergetic, challenging its alternative aspect, and confirming its importance in mitochondrial redox homeostasis.

Letter by Zhao Regarding Article, “Device-Related Complications in Transvenous Versus Subcutaneous Defibrillator Therapy During Long-Term Follow-Up: The PRAETORIAN-XL Trial”

Absolute hand determination of glycofibrils from natural sources in cryo-EM

Glycans are not only one of the four fundamental macromolecular classes that constitute life, but also the most abundant among these four across the Earth. However, compared with proteins and nucleic acids, our understanding of the structures and functional mechanisms of glycans remains limited. Moreover, it is generally challenging to obtain high-resolution three-dimensional structures of glycans. Recent studies have demonstrated the potential of the CryoSeek strategy in enabling high-throughput structural determination of glycans, thereby presenting novel avenues for their structural investigation. Meanwhile, unlike proteins, near atomic resolution density maps of glycofibrils do not inherently facilitate the determination of absolute hand, which is a prerequisite for building atomic models of glycofibrils. Existing absolute hand determination methods have severe limitations in the case of glycofibrils from natural sources. In this study, we introduce Ahaha, a straightforward and efficient method for determining such absolute hand in cryogenic electron microscopy. With their absolute hand measured by Ahaha, we built atomic models of four glycofibrils derived from a natural water sample, facilitating the study of glycans. The online service of Ahaha is available at https://cryoseek.org/ahaha .

Endothelial Transcription Factor EB Protects Against Doxorubicin-Induced Endothelial Toxicity and Cardiac Dysfunction

BACKGROUND: Doxorubicin (DOX), an effective chemotherapeutic drug for various cancers, has been demonstrated to induce cardiovascular toxicity in cancer survivors. Endothelial cell (EC) dysfunction is recognized to play a critical role in the onset and severity of cardiotoxicity associated with DOX. TFEB (transcription factor EB), a master regulator of autophagy and lysosome biogenesis, regulates cardiovascular homeostasis. In the present study, we aimed to test whether endothelial TFEB protects against EC damage and alleviates cardiac dysfunction induced by DOX treatment. METHODS: EC-specific TFEB transgenic mice, EC-specific TFEB knockout mice, and their corresponding littermate controls were administered DOX intravenously. Survival curves were generated, and cardiac functions were measured in mice. The effects of TFEB on mitochondrial reactive oxygen species production, autophagic flux, and apoptosis were evaluated in human and mouse cardiac microvascular ECs treated with DOX. RNA sequencing, single-cell RNA sequencing, and chromatin immunoprecipitation with quantitative polymerase chain reaction (ChIP-qPCR) was performed to dissect molecular mechanisms in DOX-treated ECs in vitro and in vivo. Mice with endothelium-specific deficiency of Dab2 gene (Disabled homolog 2) were subjected to measurement of cardiac function and fibrosarcoma growth under DOX treatment. RESULTS: EC-specific TFEB transgenic mice showed significantly reduced mortality and improved cardiac function, together with attenuation of perivascular fibrosis after DOX treatment. By contrast, EC-specific TFEB knockout exacerbated DOX-induced cardiac dysfunction in mice. Furthermore, we observed that TFEB enhanced autophagy and reduced oxidative stress in cardiac microvascular ECs treated with DOX. In addition, TFEB preserved EC barrier integrity, alleviated proinflammatory cytokine release from cardiac microvascular ECs, and maintained the EC–cardiomyocyte communication, contributing to the protective effects of EC TFEB on cardiomyocyte function. Mechanistically, DAB2, a clathrin- and cargo-binding endocytic adaptor protein, was identified as a TFEB target gene in ECs. Accordingly, DAB2 knockdown attenuated the inhibitory effects of TFEB on apoptosis and the secretion of proinflammatory cytokines from cardiac microvascular ECs. In vivo, EC-specific Dab2 deficiency abolished the protective effect of EC TFEB on DOX-induced cardiac dysfunction. CONCLUSIONS: Taken together, endothelial TFEB protects against EC damage and cardiac dysfunction, constituting a potential target for treating cardiotoxicity induced by DOX. Our study provides new mechanistic insights into cardiotoxicity associated with chemotherapy.

In the wake of USAID cuts, we can create a Demographic and Health Survey Program founded on more equitable data infrastructure and stronger research integrity

Letter by Shi and Zeng Regarding Article, “Partnership Model of Regionalized Care for Congenital Heart Disease in Resource-Limited Settings: Results From the ASSIST Project”

Terrestrial ecosystem nitrogen cycling in response to field warming: Global patterns and future trends

Nitrogen cycling regulates terrestrial ecosystem productivity and carbon sequestration, yet its response to climate warming remains uncertain. Here, we compiled the most comprehensive dataset to date, integrating 7,941 observations from 413 field warming experiments worldwide with random forest regression and Community Land Model (CLM) simulations. Field warming significantly accelerated nitrogen cycling, increasing N 2 O emissions (+24.7%), mineralization (+25.8%), nitrification (+51.7%), and denitrification (+41.1%). Soil inorganic nitrogen also increased, while plant nitrogen remained largely unchanged. Elevated natural abundance of 15 N indicated that warming alleviates nitrogen limitation and promotes more open nitrogen cycles. Soil moisture, ecosystem type, and warming magnitude were key drivers. N 2 O emission and nitrification further intensified with increased warming magnitude in random forest analyses. In contrast, CLM5-BGC simulated weak responses in N 2 O emissions and nitrification and negative changes in nitrogen mineralization, substantially diverging from field observations. These discrepancies highlight the omission of microbial processes and the oversimplification of large-scale ecosystem feedbacks, respectively. Uniquely, this study provides a direct comparison among empirical data, random forest regression, and CLM simulations, revealing discrepancies and their potential causes. Collectively, our findings demonstrate that terrestrial nitrogen cycling is more responsive to climate warming than previously recognized and underscore the importance of integrating multiple analytical approaches to synthesize cross-scale ecological data.

Letter by Yu and Li Regarding Article, “The Impact of Fontan Circulatory Failure on Heart Transplant Survival: A 20-Center Retrospective Cohort Study”

Efficient evaluation of optical quantum modules via two-photon high-dimensional interference

The rapid advancement of quantum information technology has increased the demand for precise testing and calibration of quantum modules, especially in optical quantum circuits where module reliability directly impacts system performance. To address this need, we propose a two-photon quantum module evaluation method based on high-dimensional Hong–Ou–Mandel interference. Our method uses multi-degree-of-freedom photon encoding to enable rapid and accurate evaluation of optical quantum modules. Compared to traditional methods such as quantum process tomography and direct fidelity estimation, our method not only simplifies implementation but also significantly minimizes the measurement resources required. Notably, the resource demands remain invariant as the system dimensionality scales, ensuring efficient evaluation even in high-dimensional quantum systems. We validated this method on a programmable silicon photonic chip, demonstrating its ability to accurately evaluate optical quantum module performance while significantly reducing resource consumption. This quantum module evaluation method holds promise for broader applications in the field of optical quantum information technologies.

Bradycardia in Athletes: New Insights

Phenotypic CRISPR screens identify NLRX1 as an essential activator of the human mitochondrial permeability transition

The mitochondrial permeability transition (mPT) is an evolutionarily conserved destructive process that permeabilizes the inner mitochondrial membrane in response to calcium overload. The molecular mechanism underlying the mPT is not established. To unambiguously identify essential proteins, we designed two phenotypic assays for mitochondrial calcium overload and applied them to FACS-based CRISPR screening in human cells, ultimately evaluating 19,113 genes. The first screen studied mitochondrial membrane potential (MMP) collapse in response to calcium overload. Top-ranked genes were the essential proteins of the mitochondrial calcium uniporter complex, MCU and EMRE, reflecting that the calcium-induced MMP collapse results from mitochondrial calcium entry and not the mPT. The second screen measured the permeability of the inner mitochondrial membrane. Here, the fluorescent interaction of a membrane impermeant ~600 Da dye and a mitochondrial-targeted HaloTag protein was studied under mPT activating conditions; calcium overload and the thiol-reactive molecule phenylarsine oxide. With secondary validation, we identified four protein-encoding genes that delayed or prevented the mPT under knockout: NF2, REST, BPTF, and NRLX1. Knockout of the nonmitochondrial proteins BPTF, NF2, or REST increased mitochondrial calcium retention capacity (CRC). However, calcium release or sensitivity to cyclosporin A (CsA) persisted, indicative of mPT sensitizers. Only knockout of the mitochondrial matrix protein, NLRX1, increased CRC, abolished calcium release, and was CsA-insensitive. This top-ranked hit of the mitochondrial permeability screen meets the definition of an essential mPT activator. Integral membrane proteins, including all previously proposed mPT candidates, were not essential activators.

Abundance of Naturally Occurring Mononuclear Diploid Cardiomyocytes Is Associated With Cardiac Regeneration

Differential disease tolerance mediates sex-biased illness severity in sepsis

Sepsis in humans, as well as mouse models of infection, demonstrates sex-biased outcomes in which males tend to have a higher incidence, higher severity, and higher mortality compared to females. Despite this important sex-bias in sepsis outcomes, little is known about its mechanistic drivers nor therapeutic implications. Much of the foundational data on sepsis pathogenesis is derived from animal studies that included only male subjects, potentially contributing to the notable paucity of successful mouse-to-human translation of sepsis therapeutics. In this study, we demonstrate that male-biased illness severity and organ dysfunction in mouse models of bacterial sepsis are mediated by impaired disease tolerance in males, involving impaired tolerogenic shifts in mitochondrial oxidative metabolism compared to females. Microbiological and immunological analyses of sepsis between males and females revealed that sex-biased disease tolerance was independent of infection resistance mechanisms, as well as canonical immune/inflammatory dysregulation. Therapeutic potentiation of mitochondrial tolerance with doxycycline neutralized sexual dimorphism of illness severity and organ dysfunction through a male-predominant treatment effect. These data reveal that biological sex is a fundamental determinant of illness severity and treatment responsiveness in sepsis through modulation of disease tolerance, which may be harnessed therapeutically to address sex-biased outcomes in sepsis.

Correction to: Histone Lactylation–Mediated Metabolic Remodeling in Vascular Smooth Muscle Cells Aggravates Aortic Aneurysm and Dissection by Promoting Lactate Accumulation

Class-I myosin responds to changes in membrane tension during clathrin-mediated endocytosis in human induced pluripotent stem cells

Clathrin-mediated endocytosis (CME) is an essential cellular process that needs to operate efficiently across a wide range of conditions. Internalization of the endocytic site involves forces generated by membrane-bound proteins and Arp2/3-mediated branched actin filament assembly to bend the plasma membrane from flat to omega-shaped. In mammalian CME, the requirement for a branched actin filament network varies depending on cell type and differences in membrane tension. However, how the actin network adapts to changes in load in order to ensure robustness of this process over a range of membrane tensions is not understood. Here, we combine live-cell imaging and superresolution microscopy of genome-edited human induced pluripotent stem cells to investigate the role of the mammalian class-I myosin, Myosin1E (Myo1E), in load adaptation. Under normal conditions, sites that recruit Myo1E are rare and exhibit slow CME dynamics. However, as membrane tension increases and CME dynamics are slowed globally, Myo1E is recruited to more sites, likely to increase actin assembly and motor activity, resulting in increased force generation to rescue stalled sites and promote internalization. Loss of Myo1E results in increased Arp2/3 complex lifetime at CME sites under normal conditions, and at high membrane tension, these sites fail to recruit as many Arp2/3 molecules. We propose that Myo1E is recruited to CME sites that have stalled due to increased membrane tension, where it helps build a more effective branched actin network by generating force through motor activity and recruiting additional Arp2/3 complexes to rescue stalled sites.

Correction to: Selective mRNA Translation: A New Player in Ferroptosis After Myocardial Infarction