Biology subjects

Couturier, N.

Publications and source records attributed to Couturier, N..

7 recordsLinked to original sources

bioRxiv2026

From silicone gel bleed chemistry to skeletal muscle and lipid alterations: clinical and in vitro evidence

Musculoskeletal symptoms are frequently reported following silicone breast implantation. However, the biological mechanisms linking implant-derived silicone exposure to skeletal muscle alterations remain poorly understood, partly because the biological effects of silicone have long been debated in the context of its biocompatibility. Here, we chemically characterized the low-molecular-weight fraction of the breast implant silicone exposome, readily released from implant gel through gel bleed, and investigated its potential biological consequences using an integrated approach combining analytical chemistry, clinical transcriptomics and histology, and controlled in vitro muscle experiments. Transcriptomic analyses of periprosthetic tissues associated with silicone implant rupture revealed unexpected myogenic and neuromuscular signatures in tissue conventionally regarded as predominantly fibrous, together with alterations in lipid metabolism and transport. These findings were supported by histological evidence of close interactions between periprosthetic tissue and skeletal muscle. Chemical analysis of the implant-gel extract detected linear siloxane L2 and cyclic siloxanes D3-D8, with tentative assignment of D9. In vitro, C2C12 cells exposed to the implant-gel extract showed up to 30% reduced viability and decreased expression of key neuromyogenic genes. Together, these findings provide convergent chemical, clinical, and experimental evidence that low-molecular-weight constituents of the breast implant silicone exposome may constitute a biologically active exposure capable of affecting skeletal muscle. The associated alterations in lipid metabolism and transport further provide a mechanistic framework for investigating the cellular handling and potential tissue distribution of hydrophobic silicone-derived species. These findings position silicone gel bleed as a biologically relevant source of chemical exposure rather than solely a material-integrity phenomenon.

bioengineering↗

bioRxiv2026

MLL3 adaptor function, not methyltransferase catalytic activity, is essential for breast tumor suppression

MLL3 (Mixed-Lineage Leukemia 3), also known as KMT2C, is one of the most frequently altered epigenetic regulators in breast cancer. MLL3 loss-of-function leads to accelerated tumor onset and growth and increased metastasis. As a large multi-domain protein, MLL3 functions as a histone methyltransferase and a nuclear protein adaptor interacting with other epigenetic proteins. Since breast cancer MLL3 mutations are often truncating mutations that lead to protein degradation, whether the MLL3 tumor suppressor activity depends on its catalytic activity or non-catalytic chromatin adaptor function remains unclear. Here, using CRISPR genetically engineered mouse mammary stem cell organoid-based breast tumor models, we dissected dosage-dependent and domain-specific functions of MLL3 in breast tumor suppression. MLL3 heterozygous loss breast tumor models revealed that MLL3 is haplo-insufficient for breast tumor suppression. Interestingly, homozygous catalytic-dead MLL3-Y4792A mutation did not accelerate tumor onset, growth, or metastasis. By contrast, G367V mutation in the PHD2 domain, which disrupts the BAP1 complex binding without affecting MLL3 protein stability, accelerated tumor onset and growth, phenocopying MLL3 loss. Mechanistically, MLL3 loss impaired chromatin localization of UTX, and genetic depletion of UTX accelerated breast tumor progression in MLL3-wildtype but not MLL3-deficient cells. Integrated RNA-seq, CUT&TAG, and ATAC-seq analyses further showed that transcriptional changes induced by MLL3 loss were more closely associated with promoter-proximal alterations in H3K27Ac, H3K27me3, and chromatin accessibility than with putative MLL3-dependent enhancer regions. Together, these findings reveal that MLL3 suppresses breast tumor initiation through a dosage-sensitive, catalytic-independent adaptor function that regulates promoter-proximal epigenetic states.

cancer biology↗

bioRxiv2026

Advanced 3D spheroid-based skin models and deep-learning based image analysis enable in-depth investigation of keratinocyte differentiation and barrier function

To date, a panel of different biological models have been used in skin research, ranging from in vivo testing to 2D and 3D cultures. Among these, organotypic skin models represent the current gold standard for preclinical dermatology and toxicology studies. However, they are variable in quality and require long maturation times and a lot of work and cells, the latter often of primary origin. Here, we propose dermal-epidermal spheroids as an alternative model that balances physiological relevance and throughput. Next to corresponding full thickness skin models, different fibroblast/keratinocyte coculture spheroids were generated. These used the commonly employed HaCaT cells as well as two recently immortalized keratinocyte cell lines, NHK-SV/TERT and NHK-E6/E7. To investigate their differentiation with detailed spatio-temporal resolution, a deep-learning segmentation-based pipeline, capable of revealing nuclear morphology and positioning as well as marker expression with single-cell precision, was developed and applied. Moreover, the formation of a functional barrier was assessed by live-imaging of Lucifer yellow diffusion. These experiments identified the NHK-E6/E7 cell line as the most and HaCaT cells as the least suitable alternative to primary keratinocytes in both spheroids and full thickness models. Furthermore, NHK-based coculture spheroids displayed functional maturation, including stratification, cornification, and barrier formation, closely recapitulating these features of corresponding full thickness models. Given the scalability and compatibility with automation, these micro-skin fibroblast/NHK-based 3D coculture spheroids might represent a promising new platform for pharmaceutical, cosmetic, and toxicological testing.

bioengineering↗

bioRxiv2024

Intratumoral CXCL12 Gradients Contextualize Tumor Cell Invasion, Migration and Immune Suppression in Breast Cancer

Although the CXCL12/CXCR4 pathway has been prior investigated for its prometastatic and immuno- suppressive roles in the tumor microenvironment, evidence on the spatiotemporal regulation of these hallmarks has been lacking. Here, we demonstrate that CXCL12 forms a gradient specifically around cancer cell intravasation doorways, also known as Tumor Microenvironment of Metastasis (TMEM) doorways, thus facilitating the chemotactic translocation of prometastatic tumor cells expressing CXCR4 toward the perivascular TMEM doorways for subsequent entry into peripheral circulation. Fur- thermore, we demonstrate that the CXCL12-rich micro-environment around TMEM doorways may cre- ate immunosuppressive niches, whereby CD8+ T cells, despite being attracted to these regions, often exhibit reduced effector functions, limiting their efficacy. While the CXCL12/CXCR4 pathway can mini- mally influence the overall composition of immune cell populations, it biases the distribution of CD8+ T cells away from TMEM doorways, justifying its prior-established role as immunosuppressive factor for CD8+ T cells. Our research suggests that the complex interactions between CXCL12 and the various tumor and immune cell types contributes not only to the completion of the initial steps of the metastatic cascade, but also offers an immunological "sanctuary" to prometastatic tumor cells homed around TMEM doorways. Overall, our study enhances our current understanding on the mechanisms, via which CXCL12 orchestrates tumor cell behavior and immune dynamics, potentially guiding future thera- peutic strategies to combat breast cancer metastasis and improve anti-tumor immunity.

cancer biology↗

bioRxiv2022

Loss of the MLL3 tumor suppressor accelerates breast tumor onset via HIF1a-induced CCL2-mediated recruitment of CCR2+ regulatory T cells

While essential gatekeepers of immune homeostasis, Foxp3+ regulatory T (Treg) cells infiltrating tumors acquire distinct phenotypes and become highly immunosuppressive, promoting tumor immune escape and growth. How this occurs and relates to tumor-driver mutations is largely uncharacterized. Herein, we created a mouse mammary stem cell-based tumor model using CRISPR gene editing in which we introduced known human cancer-driver mutations. These included functional loss of the MLL3 histone methyltransferase and p53, and constitutive PI3-kinase activation, recapitulating the genetic makeup of aggressive breast cancers. We show that MLL3 loss fosters tumorigenesis by promoting the rapid establishment of an immunosuppressive microenvironment through induction of HIF1, which increases the secretion of the chemokine CCL2 by tumor cells and the recruitment of higher numbers of Foxp3+ Treg cells via CCR2. Greater infiltration of Treg cells also correlates with MLL3 downregulation and mutations in human breast cancer biopsies. Interestingly, HIF1 enforces the differentiation of tumor-infiltrating Treg cells into highly immunosuppressive ICOShiGITRhi Blimp-1hi effector Treg cells that enable rapid tumor escape. Monoclonal antibody targeting of ICOS or GITR inhibits tumorigenesis in most mice even two months after the cessation of treatment as well as the growth of established tumors, suggesting possible therapeutic opportunities for MLL3-mutant breast cancers.

immunology↗

bioRxiv2020

SH3KBP1 scaffolds endoplasmic reticulum and controls skeletal myofibers architecture and integrity

The building block of skeletal muscle is the multinucleated muscle fiber, formed by the fusion of hundreds of mononucleated precursor cells, myoblasts. In the normal course of muscle fiber development or regeneration, myonuclei are actively positioned throughout muscular development and adopt special localization in mature fibers: regular spacing along muscle fibers periphery, raising the notion of MyoNuclear Domains (MNDs). There is now growing support for a direct connection between myonuclear positioning and normal function of muscles, but how myonuclei affects muscle function remains poorly characterized. To identify new factors regulating forces applied on myonuclei in muscles fibers, we performed a siRNA screen and identified SH3KBP1 as a new factor controlling myonuclear positioning in early phases of myofibers formation. Depletion of SH3KBP1 induces a reset of MNDs establishment in mature fibers reflected by a dramatic reduction in pairwise distance between myonuclei. We show that SH3KBP1 scaffolds Endoplasmic Reticulum (ER) in myotubes that in turn controls myonuclei velocity and localization and thus myonuclear domains settings. Additionally, we show that in later phases of muscle maturation, SH3KBP1 contributes to the formation and maintenance of Sarcoplasmic Reticulum (SR) and Transverse-tubules (T-tubules). We also demonstrate that in muscle fibers, GTPase dynamin-2 (DNM2) binds to SH3 domains of SH3KBP1. Interestingly, we observed that Sh3kbp1 mRNA is up regulated in a mouse model harboring the most frequent mutation for Autosomal Dominant CentroNuclear Myopathy (AD-CNM): Dnm2+/R465W. SH3KBP1 thus appears as a compensation mechanism in this CNM model since its depletion contributes to an increase of CNM-like phenotypes (reduction of muscle fibers Cross-section Areas (CSA) and increase in slow fibers content). Altogether our results identify SH3KBP1 as a new regulator of myonuclear domains establishment in the early phase of muscle fibers formation through ER scaffolding and later in myofibers integrity through T-tubules scaffolding/maintenance. SummaryMyonuclei are actively positioned throughout muscular development. Guiraud, Christin, Couturier et al show that SH3KBP1 scaffolds the ER through Calnexin interaction and controls myonuclei motion during early steps of muscle fibers formation. Besides SH3KBP1 participates in cell fusion and T-tubules formation/maintenance in mature skeletal muscle fibers and contributes to slow-down CNM-like phenotypes.

cell biology↗

bioRxiv2019

Muscle MACF1 maintains myonuclei and mitochondria localization through microtubules to control muscle functionalities

Skeletal muscle is made from multinuclear myofiber, where myonuclei are positioned at the periphery or clustered below neuromuscular junctions (NMJs). While mispositioned myonuclei are the hallmark of numerous muscular diseases, the molecular machinery maintaining myonuclei positioning in mature muscle is still unknown. Here, we identified microtubule-associated protein MACF1 as an evolutionary conserved regulator of myonuclei positioning, in vitro and in vivo, controlling the \"microtubule code\" and stabilizing the microtubule dynamics during myofibers maturation, preferentially at NMJs. Specifically, MACF1 governs myonuclei motion, mitochondria positioning and structure and acetylcholine receptors (AChRs) clustering. Macf1-KO in young and adult mice decreases muscle excitability and causes evolutionary myonuclei positioning alterations in adult mice, paralleled with high mitochondria content and improved resistance to fatigue. We present MACF1 as a primary actor of the maintenance of synaptic myonuclei and AChRs clustering, peripheral myonuclei positioning and mitochondria organization through the control of microtubule network dynamics in muscle fibers.

cell biology↗