Biology subjects

Gaborit, N.

Publications and source records attributed to Gaborit, N..

7 recordsLinked to original sources

bioRxiv2026

Bone Material Properties Distributions from quantitative Raman analysis: a distribution-based approach to human bone matrix characterization

Background: Bone mechanical competence depends not only on bone mass but also on the spatial organization of mineral and organic matrix properties. Whereas quantitative backscattered electron imaging (qBEI) characterizes mineral heterogeneity using Bone Mineral Density Distributions (BMDDs), no equivalent framework currently exists for describing the biochemical heterogeneity of the bone matrix by Raman microspectroscopy. Methods: We developed a quantitative Raman analysis (qRA) workflow to generate Bone Material Properties Distributions (BMPDs). Raman spectra were acquired along full-thickness line scans crossing successive bone structural units in human trabecular and cortical bone. Pixel-wise Raman-derived biochemical parameters describing collagen organization, advanced glycation end-products, glycosaminoglycans, mineral-to-matrix ratios, carbonate substitution, and mineral crystallinity were converted into normalized frequency distributions and modeled using gaussian functions. BMPDs were generated from undecalcified pMMA-embedded iliac biopsies (n=38) and routinely processed decalcified paraffin-embedded osteomedullary biopsies (n=21). The analytical framework was validated against conventional two-dimensional Raman mapping, and reproducibility, interindividual variability, and demographic influences were evaluated. Results: BMPDs were consistently well described by gaussian functions (typically R2 > 0.95), allowing extraction of three descriptors for each biochemical parameters: Mean, Peak, and Width. One-dimensional line scans showed excellent agreement with conventional two-dimensional Raman mapping while reducing acquisition time approximately 100-fold. Technical variability remained substantially lower than biological variability for all parameters, and a single trabecular line scan provided reliable estimates of BMPD descriptors for nearly all Raman-derived indices. Cortical bone exhibited narrower BMPDs than trabecular bone, indicating lower biochemical heterogeneity. Comparable BMPDs were obtained from undecalcified and routinely decalcified specimens, demonstrating robustness to tissue processing. No significant associations with age or sex were observed after correction for multiple testing. Reference BMPDs further enabled visualization and standardized quantification of deviations in representative pathological bone biopsies. Conclusions: Quantitative Raman analysis introduces BMPDs as a novel framework for assessing the spatial heterogeneity of bone extracellular matrix composition. By extending Raman microspectroscopy beyond conventional mean measurements, BMPDs provide robust, reproducible descriptors of bone material organization and establish a methodological foundation for investigating alterations of bone quality in metabolic bone diseases.

physiology↗

bioRxiv2026

Desmin p.R406W mutation is associated with arrhythmias through structural and electrophysiological remodeling

Background and AimsMutations in the desmin (DES) gene cause a variety of cardiomyopathies associated with arrhythmias, yet the electrophysiological consequences of these variants remain largely uncharacterized. The aim of this study was to investigate the pathogenic mechanisms of the de novo DES p.R406W variant, which was identified in a 9-year-old patient who suffered from severe ventricular arrhythmias and sudden cardiac death without overt structural heart disease. MethodsHuman induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the DES p.R406W variant (including the patients line) were compared to isogenic controls. Action potentials (AP) of hiPSC-CMs were recorded using patch-clamp. Furthermore, 3D engineered heart tissues (EHTs) were generated from hiPSC-CMs and their APs were recorded with sharp microelectrodes. Analytical techniques also included transmission electron microscopy (TEM) and integrated transcriptomic and proteomic profiling. Finally, a heterozygous knock-in (KI) mouse model carrying the Des p.R405W ortholog was evaluated through surface ECG, echocardiography and ex vivo cardiac optical mapping. ResultsThe DES p.R406W mutation prolonged AP duration in IM-R406W hiPSC-CMs and EHTs vs Control ones. Multi-omics analysis of EHTs revealed a dysregulation of genes and proteins involved in contractile function, cell adhesion, and electrical activity. TEM imaging revealed changes in Z-disc architecture in mutant tissues. Twenty-week-old Des p.R405W KI mice exhibited ventricular conduction slowing (prolonged QRS) and a high susceptibility to ventricular tachyarrhythmias, likely due to reentrant mechanisms. Mild hypertrophy was also observed, but only in females. ConclusionThe DES p.R406W variant is highly pathogenic, causing electrical and structural remodeling of the myocardium. This study highlights the effectiveness of hiPSC-CMs and EHTs in recapitulating the clinical phenotype of desminopathy, providing a platform for investigating the mechanisms of early-onset cardiac arrhythmias and SCD.

pathology↗

bioRxiv2025

Hypertrophic bone proliferation at enthesis induced by unilateral injection of botulinum toxin in masticatory muscles in adult rats is characterized by chondrocyte proliferation without inflammatory process at enthesis

A single injection of botulinum toxin injected in masticatory muscles induces alveolar bone loss associated with muscle enthesis hypertrophic bone proliferation. The tissular and cellular mechanisms involved in this phenomenon are unknown. Because new bone formation due to inflammation at enthesis is observed in articular disorder like spondyloarthritis, we hypothesize that an inflammatory process could explain the development of hypertrophic bone proliferation in the BTX model. The aims of the study were to test this hypothesis and to determine whether IL-17A was involved. Mature Sprague-Dawley male rats (n=36) were randomized into 4 groups. Three groups received BTX injections in right masseter and temporalis muscle. One BTX group was treated with an anti-IL17A antibody for 31 days (BTX31+antiIL17A). The two other groups were respectively sacrificed at 21 (BTX21) and 31 (BTX31) days post BTX injection. The remaining non-BTX group received anti-IL17A treatment for 31 days (control+anti-IL-17A). Alveolar bone loss and hypertrophic bone proliferation at enthesis were studied using microcomputed tomography. The presence of inflammatory process and the implication of IL17A was assessed by histology and immunohistochemistry on decalcified right side hemimandibles. Quantitative measurement of the hypertrophic bone (bone volume and thickness) showed no significant differences between the 3 BTX groups. Histology revealed the presence of chondrocytes in large hypertrophic area but no inflammatory infiltrated cells. Immunochemistry confirmed the absence of inflammatory process but positive reaction for Ki67 which is in favor of actively growing and proliferative chondrocytes. BTX-related muscle atrophy of masticatory muscle induced chondrocyte proliferation at enthesis without inflammation process.

pathology↗

bioRxiv2025

Exploring cardiac phenotypes of Drosophila orthologues of human genes associated to Brugada Syndrome (BrS)

Brugada syndrome (BrS) is a rare cardiac arrhythmic disorder with high risk of sudden cardiac death. Recent advances have identified more than 20 risk loci with complex inheritance suggesting a polygenic model for BrS inheritance. These loci are in non-coding regions located in the vicinity of cardiac-expressed genes. This complex genetic architecture and the limited understanding of BrS genetic and molecular mechanisms hinder the development of efficient prevention strategies in the context of this syndrome and are unfavorable to the implementation of therapeutic interventions. In this context, understanding the functional impact of the identified putative risk alleles is a prerequisite. Here, we used the fly model to systematically test whether orthologues of genes located near risk alleles for BrS participate to cardiac function. The fly is the simplest model with a heart muscle and is a powerful genetic model suitable for efficient screening of candidate genes, providing a whole organism-based assessment of cardiac development, structure and function. Using high-speed heart imaging platform on intact flies, we invalided the cardiac expression of the fly orthologues of human genes associated to BrS and characterized whether they are cell autonomously implicated in heart functioning. Our results provide an overview of cardiac phenotypes associated with genes potentially involved in BrS, enabling their prioritization for further investigations in mammalian models.

genetics↗

bioRxiv2024

Gene Therapy with the N-terminal Fragment of Nav1.5 for Cardiac Channelopathies: A Novel Transcomplementation Mechanism Potentiating the Cardiac Sodium Current

BACKGROUNDCardiac channelopathies, caused by mutations in ion-channel genes, can lead to sudden cardiac death (SCD) via ventricular arrhythmias. Brugada syndrome (BrS) is a rare inherited channelopathy characterized by a unique ECG pattern and a high incidence of ventricular fibrillation leading to SCD in the absence of structural heart defects. The main gene responsible for 20-25% of BrS cases is SCN5A, encoding the cardiac sodium channel -subunit Nav1.5, which carries the sodium current (INa) responsible for the rapid depolarization phase of the action potential (AP). While current treatments do not target the genetic cause of channelopathies, this study explores the therapeutic potential of overexpressing the N-terminal region of Nav1.5 (Nter) to restore electrical activity by rescuing INa, in the context of SCN5A deficiency. METHODSWe overexpressed the Nter peptide using viral vectors in Scn5a+/- mice, in CRISPR/Cas9 edited-SCN5A+/- cardiomyocytes derived from induced-pluripotent stem cells (iPSC-CMs) and in BrS patient iPSC-CMs. We assessed molecular and functional effects of Nter overexpression in vitro and in vivo by measuring Nav1.5 subcellular expression and electrophysiological activity and by recording ECGs and arrhythmias. RESULTSWhereas Scn5a+/- mice showed an impaired INa associated with a slowed-cardiac conduction characteristic of the BrS phenotype, cardiac-specific overexpression of Nter corrected AP parameters by restoring INa density in Scn5a+/- mouse cardiomyocytes. This increase in INa density was caused by a translocation of Nav1.5 to the cell membrane in Nter-overexpressing mice. Most importantly, Nter overexpression normalized atrioventricular and ventricular conduction and protected Scn5a+/- mice from arrhythmias triggered by programmed electrical stimulation. Similarly, Nter overexpression in SCN5A+/- human iPSC-CMs led to a 2-fold increase in Nav1.5 cell-surface expression, resulting in normalization of INa and AP parameters and abolition of early after depolarizations observed during spontaneous AP recordings. Similar results were obtained in iPSC-CMs derived from a BrS patient, confirming the potential of this therapy in human models. CONCLUSIONSThis study identified a novel therapeutic peptide effective in restoring cardiac excitability in animal and cellular models of BrS, paving the way for future development of therapies for life-threatening arrhythmias in patients with SCN5A deficiency.

physiology↗

bioRxiv2022

Deciphering transcriptional networks during human cardiac development

Human heart development is governed by transcription factor (TF) networks controlling dynamic and temporal gene expression alterations. Therefore, to comprehensively characterize these transcriptional regulations, day-to-day transcriptomic profiles were generated throughout the directed cardiac differentiation, starting from three distinct human induced pluripotent stem cell lines from healthy donors (32 days). We applied an expression-based correlation score to the chronological expression profiles of the TF genes, and clustered them into 12 sequential gene expression waves. We then identified a regulatory network of more than 23 000 activation and inhibition links between 216 TFs. Within this network, we observed previously unknown inferred transcriptional activations linking IRX3 and IRX5 TFs to three master cardiac TFs: GATA4, NKX2-5 and TBX5. Luciferase and co-immunoprecipitation assays demonstrated that these 5 TFs could (1) activate each others expression, (2) interact physically as multiprotein complexes and (3) together, finely regulate the expression of SCN5A, encoding the major cardiac sodium channel. Altogether, these results unveiled thousands of interactions between TFs, generating multiple robust hypotheses governing human cardiac development.

developmental biology↗

bioRxiv2019

Biasing HER4 Tyrosine Kinase Signaling with Antibodies: Induction of Cell Death by Antibody-Dependent HER4 Intracellular Domain Trafficking

HER4 isoforms have oncogenic or tumor suppressor functions depending on their susceptibility to proteolytic cleavage and HER4 Intracellular Domain (4ICD) translocation. Here, we report that the NRG1 tumor suppressor mechanism through the HER4 JMa/CYT1 isoform can be mimicked by the agonist anti-HER4 antibody C6. NRG1 induced cleavage of poly(ADP-ribose) polymerase (PARP) and sub-G1 DNA fragmentation, and also reduced the metabolic activity of HER3-negative/HER4-positive cervical (C-33A) and ovarian (COV318) cancer cells. This effect was confirmed in HER4 JMa/CYT1-, but not JMa/CYT2-transfected BT549 triple-negative breast cancer cells. NRG1 favored 4ICD cleavage and retention in mitochondria in JMa/CYT1-transfected BT549 cells, leading to Reactive Oxygen Species (ROS) production through mitochondrial depolarization. Similarly, the anti-HER4 antibody C6, which binds to a conformational epitope located on aa 575-592 and 605-620 of HER4 domain IV, induced 4ICD cleavage and retention in mitochondria, and mimicked NRG1-mediated effects on PARP cleavage, ROS production, and mitochondrial membrane depolarization in cancer cells. In vivo, C6 reduced growth of COV434 and HCC187 tumor cell xenografts in nude mice. Biasing 4ICD trafficking to mitochondria with anti-HER4 antibodies to mimic NRG1 suppressor functions could be an alternative anti-cancer strategy.

cancer biology↗