Biology subjects

Laporte, J.

Publications and source records attributed to Laporte, J..

11 recordsLinked to original sources

bioRxiv2025

DNM2-CMT neuropathy stems from disrupted Schwann cell function and shows limited therapeutic reversibility

Dominant loss-of-function mutations in DNM2 cause Charcot-Marie-Tooth (CMT) neuropathy characterized by sensory and motor deficits associated with myelin and/or axonal abnormalities and muscle atrophy. Increasing DNM2 activity from embryogenesis has been reported to ameliorate neuromuscular phenotypes in the Dnm2K562E/+ CMT mouse; however, this model displays predominantly muscle pathology and limited nerve involvement, precluding rigorous evaluation of neuropathic mechanisms and potential therapies. Here, we performed comprehensive behavioral, electrophysiological, histological and molecular analyses to characterize the Dnm2K562E/SC- mouse, which combines systemic heterozygosity for the common K562E mutation together with Schwann cell (SC)-specific deletion of wild-type Dnm2. This model faithfully reproduces key clinical and pathological features of DNM2-CMT, including motor deficits, reduced general force and coordination, and severe sensory and motor conduction deficits associated with axonal loss, demyelination, and inflammation. Mechanistically, we delineate a coherent pathological sequence that explains the profound functional deficits. In particular, a downregulation of the transcription factor EGR2, a master regulator of myelin gene expression, and of the myelin protein MPZ correlates with demyelination. To evaluate the therapeutic potential of DNM2 supplementation, post-symptomatic intrathecal delivery of AAV9-DNM2 driven by the Schwann cell-specific MPZ promoter was performed at 4 weeks. Although DNM2 expression increased in peripheral nerves ([~]1.9-fold), no significant improvements were observed across behavioural, electrophysiological, structural, or molecular parameters. Together, these findings establish the Dnm2K562E/SC- mouse as a robust preclinical model, recapitulating key features of DNM2-CMT, and provides crucial insight into the biological and temporal constraints that must guide future therapeutic strategies for DNM2-CMT.

neuroscience↗

bioRxiv2025

Muscle-specific DNM2 overexpression improves Charcot-Marie-Tooth disease in vivo and reveals a narrow therapeutic window in skeletal muscle

Charcot-Marie-Tooth disease (CMT) caused by dominant loss-of-function mutations in DNM2, encoding the GTPase dynamin-2, impairs motor and sensory function. However, the respective contributions of muscle and nerve pathology, and the therapeutic potential of increasing DNM2 expression, remain unresolved. We evaluated tissue-targeted and systemic approaches to increase DNM2 in a mouse model carrying the common K562E-CMT mutation. Muscle-specific DNM2 overexpression from embryogenesis in Dnm2K562E/+ mice ameliorated desmin and integrin mislocalization, membrane trafficking defects, mitochondrial abnormalities, and fibrosis in skeletal muscle, resulting in improved locomotor performance despite persistent muscle atrophy. Conversely, systemic postnatal AAV delivery of human DNM2 increased DNM2 in muscle but failed to transduce nerves, and paradoxically worsened the muscle pathology, producing centronuclear myopathy-like features. These findings reveal a primary pathogenic impact of DNM2-CMT mutation within skeletal muscle, independent of nerve involvement. Collectively, they underscore that precise DNM2 dosage is critical for neuromuscular homeostasis and reveal a narrow therapeutic window for safe and effective therapeutic intervention. This paradox, in which efforts to compensate for a loss-of-function neuropathy risk inducing a gain-of-function myopathy, highlights the need for tightly controlled modulation of DNM2 activity in future therapeutic strategies.

neuroscience↗

bioRxiv2025

BIN1 overexpression rescues cardiac but not skeletal muscle defects in a mouse model of caveolinopathy

BackgroundMutations in CAV3, encoding caveolin-3, cause caveolinopathies, rare genetic disorders affecting both skeletal and cardiac muscle. Caveolin-3 contributes to T-tubule formation and excitation-contraction coupling. BIN1 (amphiphysin 2), a membrane-shaping protein critical for T-tubule integrity, has shown therapeutic promise in congenital myopathies and heart dysfunction. To date, there are no therapy for caveolinopathies. MethodsWe evaluated the therapeutic impact of BIN1 overexpression in Cav-3 knockout mice, a model recapitulating key features of human caveolinopathy. We assessed skeletal and cardiac function, T-tubule morphology, mitochondria, and gene expression using histological, physiological, and molecular approaches. ResultsWe found Cav-3-/- mice displayed skeletal muscle weakness, T-tubule disorganization, and mitochondrial abnormalities, alongside cardiac diastolic dysfunction and myofibrillar disarray. While BIN1 overexpression failed to improve skeletal muscle strength, T-tubule structure, or fiber atrophy, it corrected nuclear positioning and partially restored mitochondrial markers. In contrast, BIN1 robustly rescued cardiac performance, restoring end-diastolic volume, cardiac output, and sarcomeric integrity. Expression profiling revealed greater dysregulation of excitation-contraction coupling and atrogene pathways in skeletal than in cardiac muscle. Cavin-4, a BIN1-interacting protein, was selectively dysregulated in Cav3-/- muscle, suggesting a mechanistic barrier to BIN1-mediated rescue in this tissue. ConclusionsThese findings identify tissue-specific differences in the molecular consequences of caveolin-3 loss and demonstrate that BIN1 overexpression effectively rescues cardiac, but not skeletal, manifestations of caveolinopathy. Our results support BIN1 as a promising gene therapy target for inherited cardiomyopathies, while highlighting the need for alternative strategies in skeletal muscle.

pathology↗

bioRxiv2025

Elucidating the molecular landscape of centronuclear myopathies in mouse models: an integrative multi-omics and network analysis

Centronuclear myopathies (CNM) are rare inherited muscle disorders characterized by muscle atrophy, weakness, and altered muscle fiber structure, primarily due to mutations in genes like MTM1, DNM2, and BIN1. The pathomechanisms implicated in CNM are only partially understood, and no curative therapies are available for patients. This study exploits a unique multi-omics dataset and network-based analyses to elucidate the molecular pathways involved in CNM. First, we performed Weighted Gene Co-expression Network Analysis (WGCNA) to identify gene modules correlated with CNM phenotypes. We find that modules correlated to a positive muscular phenotype were enriched for genes involved in muscle contraction, RNA processes and oxidative phosphorylation, while modules associated with impaired muscle structure and function were enriched in immune response, innervation, vascularization processes, and fatty acid oxidation. Next, we integrated transcriptomic, proteomic, and metabolomic data from the Mtm1-/y mouse model with public knowledge bases using a multilayer network approach and explored the network using a random walk with restart approach. This study revealed novel metabolites that could be targeted through dietary supplementation as potential therapeutic strategies. Our findings demonstrate how multi-omics network analyses can reveal new aspects of CNM pathomechanisms and identify avenues for intervention.

bioinformatics↗

bioRxiv2023

Affinity-ranking BIN1 interactions and screening natural BIN1 variants that may cause neuromuscular disorders

Truncation of the protein-protein interaction SH3 domain of the membrane remodeling Bridging Integrator 1 (BIN1, Amphiphysin 2) protein leads to centronuclear myopathy. Here, we assessed the impact of a set of naturally observed, previously uncharacterized BIN1 SH3 domain variants using conventional in vitro and cell-based assays monitoring the BIN1 interaction with dynamin 2 (DNM2) and identified potentially harmful ones that can be also tentatively connected to neuromuscular disorders. However, SH3 domains are typically promiscuous and it is expected that other, so-far unknown partners of BIN1 exist besides DNM2, that also participate in the development of centronuclear myopathy. In order to shed light on these other relevant interaction partners and to get a holistic picture of the pathomechanism behind BIN1 SH3 domain variants, we used affinity interactomics. We identified hundreds of new BIN1 interaction partners proteome-wide, among which many appear to participate in cell division, suggesting a critical role of BIN1 in the regulation of mitosis. Finally, we show that the identified BIN1 mutations indeed cause proteome-wide affinity perturbation, signifying the importance of employing unbiased affinity interactomic approaches.

biochemistry↗

bioRxiv2022

IMPatienT: an integrated web application to digitize, process and explore multimodal patient data.

Medical acts, such as imaging, lead to the production of several medical text report that describes the relevant findings. This induces multimodality in patient data by linking image data to free-text and consequently, multimodal data have become central to drive research and improve diagnosis. However, the exploitation of patient data is challenging as the ecosystem of analysis tools is fragmented depending on the type of data (images, text, genetics), the task (processing, exploration) and domains of interest (clinical phenotype, histology). To address the challenges, we present IMPatienT (Integrated digital Multimodal PATIENt daTa), a simple, flexible and open-source web application to digitize, process and explore multimodal patient data. IMPatienT has a modular architecture to: (i) create a standard vocabulary for a domain, (ii) digitize and process free-text data, (iii) annotate images and perform image segmentation, and (iv) generate a visualization dashboard and perform diagnosis suggestions. We showcased IMPatienT on a corpus of 40 simulated muscle biopsy reports of congenital myopathy patients. As IMPatienT relies on a user-designed vocabulary, it can be adapted to any domain of research and can be used as a patient registry for exploratory data analysis (EDA). A demo instance of the application is available at https://impatient.lbgi.fr/.

bioinformatics↗

bioRxiv2022

BIN1/Amphiphysin 2 and ezrin drive filopodia-like structures in myoblasts

Amphiphysin 2 (BIN1) is a membrane and actin remodeling protein mutated in congenital and adult centronuclear myopathies. Here, we report an unexpected function of this N-BAR domain protein BIN1 in filopodia formation. We demonstrated that BIN1 expression is necessary and sufficient to induce filopodia formation. BIN1 is present at the base of forming filopodia and all along filopodia, where it colocalizes with F-actin. We identify that BIN1-mediated filopodia formation requires IRSp53, which allows its localization at negatively-curved membrane topologies. Our results show that BIN1 bundles actin in vitro. Finally, we identify that BIN1 regulates the membrane-to-cortex architecture and functions as a molecular platform to recruit actin-binding proteins, dynamin and ezrin, to promote filopodia formation.

cell biology↗

bioRxiv2019

Functional analyses of STIM1 mutations reveal a common pathomechanism for tubular aggregate myopathy and Stormorken syndrome

Tubular aggregate myopathy (TAM) is a progressive disorder essentially involving muscle weakness, cramps, and myalgia. TAM clinically overlaps with Stormorken syndrome (STRMK), associating TAM with miosis, thrombocytopenia, hyposplenism, ichthyosis, short stature, and dyslexia. TAM and Stormorken syndrome arise from gain-of-function mutations in STIM1 or ORAI1, both encoding key regulators of Ca2+ homeostasis, and mutations in either gene results in excessive Ca2+ entry. The pathomechanistic similarities and differences of TAM and Stormorken syndrome are only partially understood. Here we provide functional in cellulo experiments demonstrating that STIM1 harboring the TAM D84G or the STRMK R304W mutation similarly cluster and exert a dominant effect on the wild-type protein. Both mutants recruit ORAI1 to the clusters, induce major nuclear import of the Ca2+-dependent transcription factor NFAT, and trigger the formation of circular membrane stacks. In conclusion, the analyzed TAM and STRMK mutations have a comparable impact on STIM1 protein function and downstream effects of excessive Ca2+ entry, highlighting that TAM and Stormorken syndrome involve a common pathomechanism.

molecular biology↗

bioRxiv2018

Differential physiological role of BIN1 isoforms in skeletal muscle development, function and regeneration

Skeletal muscle development and regeneration are tightly regulated processes. How the intracellular organization of muscle fibers is achieved during these steps is unclear. Here we focus on the cellular and physiological roles of amphiphysin 2 (BIN1), a membrane remodeling protein mutated in both congenital and adult centronuclear myopathies, that is ubiquitously expressed and has skeletal muscle-specific isoforms. We created and characterized constitutive, muscle-specific and inducible Bin1 homozygous and heterozygous knockout mice targeting either ubiquitous or muscle-specific isoforms. Constitutive Bin1-deficient mice died at birth from lack of feeding due to a skeletal muscle defect. T-tubules and other organelles were misplaced and altered, supporting a general early role of BIN1 on intracellular organization in addition to membrane remodeling. Whereas restricted deletion of Bin1 in unchallenged adult muscles had no impact, the forced switch from the muscle-specific isoforms to the ubiquitous isoforms through deletion of the in-frame muscle-specific exon delayed muscle regeneration. Thus, BIN1 ubiquitous function is necessary for muscle development and function while its muscle-specific isoforms fine-tune muscle regeneration in adulthood, supporting that BIN1 centronuclear myopathy with congenital onset are due to developmental defects while later onset may be due to regeneration defects.

pathology↗

bioRxiv2018

BIN1 recovers tauopathy-induced long-term memory deficits in mice and interacts with Tau through Thr348 phosphorylation

The bridging integrator 1 gene (BIN1) is a major genetic risk factor for Alzheimers disease (AD). In this report, we investigated how BIN1-dependent pathophysiological processes might be associated with Tau. We first generated a cohort of control and transgenic mice either overexpressing human MAPT (TgMAPT) or both human MAPT and BIN1 (TgMAPT;TgBIN1), which we followed-up from 3 to 15 months. In TgMAPT;TgBIN1 mice short-term memory deficits appeared earlier than in TgMAPT mice; however - unlike TgMAPT mice - TgMAPT;TgBIN1 mice did not exhibit any long-term or spatial memory deficits for at least 15 months. After sacrifice of the cohort at 18 months, immunohistochemistry revealed that BIN1 overexpression prevents both Tau mislocalization and somatic inclusion in the hippocampus, where an increase in BIN1-Tau interaction was also observed. We then sought mechanisms controlling the BIN1-Tau interaction. We developed a high-content screening approach to characterize modulators of the BIN1-Tau interaction in an agnostic way (1,126 compounds targeting multiple pathways), and we identified - among others - an inhibitor of Calcineurin, a Ser/Thr phosphatase. We determined that Calcineurin dephosphorylates BIN1 on a Cyclin-dependent kinase phosphorylation site at T348, promoting the open conformation of the neuronal BIN1 isoform. Phosphorylation of this site increases the availability of the BIN1 SH3 domain for Tau interaction, as demonstrated by nuclear magnetic resonance experiments and in primary neurons. Finally, we observed that the levels of the neuronal BIN1 isoform were decreased in AD brains, whereas phospho-BIN1(T348):BIN1 ratio was increased, suggesting a compensatory mechanism. In conclusion, our data support the idea that BIN1 modulates the AD risk through an intricate regulation of its interaction with Tau. Alteration in BIN1 expression or activity may disrupt this regulatory balance with Tau and have direct effects on learning and memory.

neuroscience↗

bioRxiv2018

BIN1 genetic risk factor for Alzheimer is sufficient to induce early structural tract alterations in entorhinal cortex-dentate gyrus pathway and related hippocampal multi-scale impairments

Genetic factors are known to contribute to Late Onset Alzheimers disease (LOAD) but their contribution to pathophysiology, specially to prodomic phases accessible to therapeutic approaches are far to be understood. To translate genetic risk of Alzheimers disease (AD) into mechanistic insight, we generated transgenic mouse lines that express a [~]195 kbp human BAC that includes only BIN1, a gene associated to LOAD. This model gives a modest BIN1 overexpression, dependent of the number of BAC copies. At 6 months of age, we detected impaired entorhinal cortex (EC)-hippocampal pathways with specific impairments in EC-dentate gyrus synaptic long-term potentiation, dendritic spines of granular cells and recognition episodic memory. Structural changes were quantified using MRI. Their whole-brain functional impact were analyzed using resting state fMRI with a hypoconnectivity centered on entorhinal cortex. These early phenotype defects independent of any changes in A-beta can be instrumental in the search for new AD drug targets.

neuroscience↗