Introduction

In the final stages of mitotic cell division, the narrow cytoplasmic canal that connects the two daughter cells is cut, and this is called abscission. However, sometimes chromatin bridges can arise during anaphase and persist in cytokinesis, and these are often the result of incomplete DNA replication or fusions of dicentric chromosomes. Chromatin bridges activate the abscission checkpoint, which is a mechanism that prolongs abscission in order to provide cells with enough time to resolve DNA bridges, and this has been linked to tumorigenesis. The abscission checkpoint prevents chromosome breakage if the cytoplasmic canal is cut, or tetraploidization in the case of furrow regression.

Methods

We performed point mutations in DNA constructs, reduced the levels of endogenous proteins with siRNAs, and used FISH and TUNEL. We also used confocal and time-lapse microscopy.

Results

We recently showed that the Mre11-Rad50-Nbs1 complex activates the ATM kinase, and this activates the Chk2 kinase in order to promote CPC localization to the midbody in cytokinesis with chromatin bridges. In this study, we show that Topoisomerase IIa (Top2a) localizes on DNA knots, which are regions of tangled DNA near the midbody, and creates abortive Top2ccs that are degraded in the proteasome. The degradation of Top2ccs is necessary for the localization of Rad17 on chromatin bridges. Rad17 then recruits the Mre11-Rad50-Nbs1 complex and activates downstream effector proteins to ensure the integrity of the chromatin bridges. Top2a-deficient cells exhibit reduced localization of the Mre11-Rad50-Nbs1 complex, Chk2, and the CPC complex and an increased frequency of broken DNA bridges. Interestingly, bridges derived from dicentric chromosomes do not possess knots or Top2ccs and are incapable of activating the abscission checkpoint.

Conclusions

We identified a new mechanism that cells use to recognize chromatin bridges during cytokinesis by creating abortive Top2ccs located on DNA knots to safeguard genome integrity and protect against tumorigenesis.

Knee joint injuries, including those affecting the anterior cruciate ligament (ACL), meniscus, and cartilage, present significant challenges in sports medicine and orthopedics. Understanding the cellular and molecular mechanisms underlying these injuries is essential for developing effective therapeutic strategies. This systematic review explores the cell biology of knee joint injuries, focusing on the effects of early mechanical loading. We examine diffierent types of knee injuries, cellular responses to mechanical loading, the signaling pathways involved, and implications for treatment and rehabilitation. This comprehensive synthesis aims to provide insights into optimizing rehabilitation protocols and developing novel therapeutic approaches.

Knee joint injuries are prevalent among athletes and the general population, often resulting from trauma, overuse, or degenerative processes. The knee joint, a complex and critical structure for mobility, is susceptible to various injuries, including ligament tears, meniscal damage, and cartilage degradation. Among these, anterior cruciate ligament (ACL) injuries are particularly common and frequently require surgical intervention. Recent research has underscored the importance of early mechanical loading in the rehabilitation process, which can significantly influence cellular responses, tissue repair, and remodeling. This review systematically examines current knowledge on the cellular mechanisms affected by early mechanical loading in knee joint injuries, providing valuable insights into potential therapeutic strategies.

The BBB is a natural barrier located in the endothelial cells of the cerebral microvessels (BMECs) that restricts exchanges between the bloodstream and the cerebral parenchyma. The integrity of the BBB is vital for preserving cerebral homeostasis, and neuroinflammatory processes alter the physical and/or metabolic properties of this barrier. The brain pericyte, which shares a common basement membrane with BMECs, has been shown to be a major cell type involved in the induction and maintenance of the BBB's main features. This presentation will review the role and intercellular interactions of human brain pericytes (hBPs) with the cells of the neurovascular unit, and particularly BMECs, based on data generated within the lab using proteomics, cell physiology, and studies of extracellular vesicles (EVs). The protein pattern of hBPs is modified once they are cocultured with BMECs, highlighting a metabolic switch induced by BMECs on hBPs. A stimulation of EV biogenesis is observed, indicating a potential need for a hBP-derived cell–cell communication through EVs. The mechanisms of interaction between BMECs and hBP-derived EVs are in favor a clathrin-coated pit-mediated endocytosis. Under inflammation, hBP-derived EVs exhibit a modified protein pattern compared to untreated EVs and induce a dysregulation of trans-endothelial electric resistance (TEER) on BMECs.

Despite their former reputation as a contaminant for BBB modeling in vitro, hBPs remain of importance for maintaining the BBB phenotype. BMECs also modulate the functions and developmental fates of hBPs. This work opens perspectives on the role of hBP-derived EVs on BBB feature regulation.

Metastatic neuroblastoma (NB) is one of the most challenging childhood cancers to treat, with a high rate of relapse despite aggressive therapies. Most NB cells express disialoganglioside GD2, a tumor-specific antigen with limited expression in normal tissues. While GD2-targeting monoclonal antibodies have shown promising clinical success, a significant number of patients still experience relapse. This is thought to be due, in part, to heterogeneous or low GD2 expression, which complicates the effectiveness of immunotherapies. However, studying GD2-targeted treatments and metastasis in NB is hindered by a lack of suitable in vitro models. Current 2D culture systems are limited in their ability to mimic the complex environment of metastatic tumors, and murine NB cells typically lose GD2 expression when cultured. To overcome these challenges, I have developed a novel 3D cell culture system known as "tumorspheres." This model allows NB cells to grow in a more physiologically relevant environment and better replicates the conditions of tumor metastasis. Preliminary results demonstrate that tumorspheres retain high GD2 expression and show significant growth and motility within a matrix scaffold, mimicking in vivo tumor behavior more accurately than traditional 2D models. Importantly, these tumorspheres can be formed from a mix of GD2-positive and GD2-negative cells, enabling the study of antigenic heterogeneity and its impact on therapeutic resistance. Additionally, tumorspheres can be implanted subcutaneously into mice to promote in vivo tumor growth, further enhancing their utility as a model for studying neuroblastoma metastasis and immunotherapy. This new 3D model offers a more representative platform for investigating GD2-targeted therapies and tumor metastasis, with the potential to advance our understanding of treatment resistance and lead to more effective strategies for combating metastatic neuroblastoma.

Introduction
Cockayne syndrome (CS) is a rare, premature aging disorder caused by mutations in the CSA and CSB genes, which affect DNA repair and transcription. CS patients frequently exhibit kidney abnormalities, but the molecular mechanisms underlying renal dysfunction remain poorly understood. Recent studies have implicated NAD+ biosynthesis, a critical pathway for cellular metabolism and the stress response, in CS pathogenesis.

Methods
This study utilized CS mouse models to investigate their renal pathology and the role of NAD+ biosynthesis. RNA sequencing was performed to analyze the differential gene expression, with a focus on NAD+ metabolism. Human kidney proximal tubular epithelial cells (HK-2) were used to validate our findings through siRNA knockdown of CSA/B. Our techniques included immunohistochemistry, NAD+ quantification, Western blotting, and chromatin immunoprecipitation (ChIP).

Results
The CS mice exhibited renal atrophy, fibrosis, and tubular epithelial cell abnormalities. RNA sequencing revealed impaired NAD+ biosynthesis pathways, with significant downregulation of quinolinate phosphoribosyl transferase (QPRT), a key enzyme in de novo NAD+ biosynthesis. Mechanistically, CSA/B deficiency stabilized ATF3, a transcriptional repressor, leading to QPRT downregulation and NAD+ depletion. These findings were confirmed in the HK-2 cells, where CSA/B knockdown recapitulated the effects on the QPRT expression and NAD+ levels.

Conclusions
Our study demonstrates that CS-related kidney dysfunction is driven by impaired NAD+ biosynthesis, mediated through ATF3-dependent QPRT repression. These findings provide novel insights into the molecular basis of renal pathology in CS and suggest potential therapeutic strategies targeting NAD+ metabolism for alleviating renal complications.

Introduction

Extracellular vesicles (EVs), including exosomes, are emerging as key mediators of intercellular communication, transferring bioactive molecules such as microRNAs, proteins, and lipids. Among non-neuronal cells, Schwann cells, oligodendrocytes, and satellite glial cells (SGCs) release EVs with distinct neuroprotective and pain-relieving properties. These EVs play critical roles in modulating inflammation, supporting neuronal repair, and regulating pain pathways, offering innovative therapeutic avenues for chronic pain management and neural repair.

Methods

A scoping review was conducted by systematically searching the PubMed, Scopus, and Web of Science databases. Studies published up to November 2024 were screened to identify evidence on Schwann cell-, oligodendrocyte-, and SGC-derived EVs. A total of 15 key studies were included, focusing on their cargo, functional mechanisms, and therapeutic applications.

Results

Schwann cell-derived EVs are enriched with neuroprotective microRNAs such as miR-21 and miR-146a, which reduce pain by regulating inflammation and promoting neuronal survival. They also carry proteins like brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), enhancing neuronal repair. Oligodendrocyte-derived EVs deliver proteins such as myelin basic protein (MBP) and proteolipid protein (PLP), which are essential for neuronal stability and repair, as well as superoxide dismutase (SOD), which mitigates oxidative stress. SGC-derived EVs, while also carrying miR-21 and miR-146a, modulate neuronal hyperexcitability and inflammation uniquely through cytokines such as interleukin-10 (IL-10), amplifying their pain-relieving effects.

Conclusion

This review highlights the distinctive roles of Schwann cell-, oligodendrocyte-, and SGC-derived EVs in alleviating pain and supporting neural health. It identifies key research gaps, including the need for standardized methodologies and deeper characterization of EV cargo. These findings emphasize the therapeutic potential of EVs as innovative tools for chronic pain treatment and neural regeneration, underscoring their translational value for future research and clinical applications.

Introduction: Access to space has significantly increased over the last decade, and with this comes the need for comprehensive knowledge about the effects exerted by altered gravitational conditions on human physiology and reproductive health. However, it should be highlighted that our knowledge about the effects of altered gravitational force on germ cells is still very poor. In this study, we exploited Reverse-Phase Protein microArrays (RPPAs), a biased (phospho-)proteomic approach, to investigate the impact of simulated microgravity (SμG) and hypogravity (ShG) on two human male germ cell lines, TCam-2 and NT2D1. Methods: TCam-2 and NT2D1 cell lines were exposed to SμG and ShG conditions using a Random Positioning Machine for 3, 24, and 72 hours. RPPA analysis was conducted using a panel of 130 antibodies selected to investigate a broad number of pathways potentially affected by altered gravity conditions. Results: The data analysis revealed that the exposure of both TCam-2 and NT2D1 cells to altered gravity induced significant (phospho-)proteomic changes. In particular, SμG induced early-phase alterations (3–24 hours), mostly characterized by the upregulation of some key regulators of signaling pathways, whereas longer SμG exposure (72 hours) resulted in the downregulation of other signaling proteins. ShG elicited minor changes, mostly characterized by reduced protein expression. The key pathways affected included cytoskeletal dynamics, proliferation, apoptosis, and autophagy. Notably, cell viability was not significantly impacted, suggesting compensating adaptation mechanisms to altered gravitational conditions. Conclusions: These findings indicate that (phospho-)proteomic responses to simulated gravity conditions were transient and non-persistent, demonstrating that human male germ cells exhibit resilience and adaptative capacity to cope with altered gravitational environments. This study provides valuable preliminary insights into the cellular and molecular mechanisms involved in gravity sensing and adaptation, which is crucial for developing countermeasures to ensure reproductive health and functionality during long-duration space missions for astronauts but also for the health of their future offspring.

The regulated production of mitochondrial reactive oxygen species (mtROS) is vital for maintaining optimal liver health. The mtROS-mediated maintenance of cell function(s) is through the induction of oxidative eustress signals, which are transmitted through the site-specific cysteine modifications. By contrast, the sustained overgeneration of mtROS triggers oxidative distress, resulting in the manifestation of metabolic diseases like non-alcoholic fatty liver disease (NAFLD) and the progression of cancer. Therefore, it is crucial to understand precisely how mitochondria generate mtROS, how its production is regulated, and how dysfunction in these regulatory mechanisms may cause NAFLD and its related disorders. Complexes I and III of the electron transport chain (ETC) are viewed as the primary mtROS sources in mammalian cells. However, we recently generated compelling evidence showing that TCA cycle enzyme α-ketoglutarate dehydrogenase (KGDH), and not the ETC, is the main mtROS supplier in hepatocytes. We found that KGDH is a main mtROS source when hepatic mitochondria are fueled with oxidizable substrates and is a main source of oxidative stress in the livers of mice subjected to dietary fat overload. Additionally, we discovered that mtROS generation by KGDH is controlled by reversible protein S-glutathionylation, which is catalyzed by glutaredoxin-2 (Glrx2). In this context, the oxidation of the glutathione (GSH) pool S-glutathionylates KGDH to shut down mtROS generation. This creates a self-contained negative feedback loop for the redox regulation of mtROS production. Recently, we showed that the manipulation of the Glrx2 pathway protects from diet-induced NAFLD development through the dynamic inhibition of KGDH-mediated mtROS hyper-generation by S-glutathionylation. In this presentation, I will elaborate on the importance of these findings in understanding the manifestation of NAFLD and how the targeted and dynamic redox modification of KGDH with mitochondria-targeted drugs can mitigate the onset of this disease through the dynamic inhibition of mtROS hyper-production by redox modifications.

Diabetes mellitus (DM) is a global public health issue causing systemic dysregulations, including severe liver complications. Type 2 diabetes (DM2) patients show elevated annexin A1 (AnxA1) levels, and in murine DM2 models, AnxA1 mitigates insulin resistance effects like hepatosteatosis. However, its role in DM1 is underexplored. This study investigates AnxA1's role in hepatocyte biology in a streptozotocin (STZ)-induced DM mouse model. Male C57BL/6 mice (WT and AnxA1-/-) were divided into control (CTR) and DM groups. DM was induced via STZ injection (65 mg/kg for 5 days). After 12 weeks, livers were collected for analysis. DM WT and AnxA1-/- mice showed weight loss and increased blood glucose, reflecting typical diabetic metabolic disruptions. Morphological evaluations revealed normal hepatocytes in WT CTR mice, while 70% of AnxA1-/- CTR mice showed cytoplasmic vacuolation. In DM groups, 50% of WT mice had vacuolated, damaged hepatocytes, increasing to 75% in AnxA1-/- DM mice, highlighting AnxA1's protective role. Hepatocyte glycogen levels were lower in DM mice, especially AnxA1-/-. Collagen deposition in the centrolobular veins and portal triads was higher in AnxA1-/- DM mice, indicating worsened fibrosis without AnxA1. Both DM WT and AnxA1-/- livers showed reduced fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGF-A), suggesting impaired regeneration. Inflammation varied between genotypes: WT DM mice had higher IL-10 and TNF-α, while AnxA1-/- DM mice showed increased monocyte chemoattractant protein-1 (MCP-1). Oxidative stress markers indicated increased reactive oxygen species (ROS) in AnxA1-/- DM hepatocytes, with differing trends in superoxide dismutase (SOD) and catalase (CAT) activities. Metabolites linked to the tyrosine, malate-aspartate, taurine, and hypotaurine pathways stood out in AnxA1 knockout mice, suggesting that these pathways are key in AnxA1-deficient mice. This highlights AnxA1's role in liver protection under diabetic conditions.

Introduction:
Inherited retinal dystrophies (IRDs) represent a heterogeneous group of genetic disorders characterized by a progressive degeneration of photoreceptors and retinal function, leading to vision loss. Recent research emphasizes the importance of modifier genes in modulating disease phenotypes, with CACNG8, which encodes the TARP γ-8 auxiliary subunit of AMPA receptors, emerging as a potential player. TARP γ-8, essential in modulating AMPA receptor function, may influence neural signaling pathways critical for retinal health. This study integrates genetic, molecular, and structural approaches to elucidate CACNG8's role in IRDs, aligning with key themes of cellular signaling and proteasomal degradation.

Methods:
A cohort of patients diagnosed with IRDs was subjected to targeted genetic screening for CACNG8 variants. Genomic DNA was extracted and analyzed using Sanger sequencing. Computational tools such as AlphaFold3 facilitated molecular docking and 3D structural modeling of wild-type and mutant TARP γ-8 protein complexes. Comparative analyses assessed receptor–ligand binding dynamics, hydrogen bond networks, and structural integrity across various CACNG8 variants, such as p.Arg123Ter and p.Leu96Val-Val102Met. Additionally, in silico predictions evaluated potential disruptions in AMPA receptor signaling pathways.

Results:
This study identified several novel and known variants in CACNG8 associated with altered protein functionality. Structural analysis highlighted significant deviations in receptor–ligand interaction profiles, particularly in mutants like p.Leu96Val-Arg123Ter. These mutations disrupted hydrogen bonding and impaired receptor desensitization recovery, pivotal in retinal synaptic plasticity. Pathway analysis suggested a cascade of signaling defects linked to reduced proteasomal degradation efficiency and impaired protein quality control, likely contributing to neuroretinal degeneration.

Conclusions:
This study positions CACNG8 as a modifier gene within IRD pathophysiology, with specific variants correlating with altered AMPA receptor function and cellular signaling disruption. These findings provide a molecular basis for understanding IRD variability, highlighting the interplay between genetic and proteomic factors in shaping retinal pathology and resonating with emerging themes in cellular neurobiology.