Biology subjects

Brunet, S.

Publications and source records attributed to Brunet, S..

5 recordsLinked to original sources

bioRxiv2026

A combinatorial EVs-miRNA signature mediates the anti-tumoral activity of NFAT3-regulated extracellular vesicles in aggressive cancers.

Aggressive cancers such as triple-negative breast cancer (TNBC) and pancreatic cancer remain difficult to treat because their malignant behavior is driven by complex gene networks rather than single oncogenic targets. Here, we identify an extracellular vesicle (EV)-associated miRNA signature functionally linked to NFAT3 activity and demonstrate its ability to suppress tumor aggressiveness. Functional analyses revealed that a combination of fifteen miRNAs (miR-Comb 15) was required to fully reproduce the anti-tumoral effects of NFAT3-regulated EVs across TNBC and pancreatic cancer models, whereas individual miRNAs showed only partial activity. These effects were associated with coordinated regulation of validated target genes controlling proliferation and invasion, supporting a network-modulating mechanism of action. To facilitate therapeutic translation, we used EVs derived from HEK 293T cells, a non-tumoral, scalable, and readily engineerable EV source. Using an optimized exogenous pH-gradient loading strategy, miR-Comb 15 was efficiently incorporated into EVs without affecting vesicle integrity or intrinsic bioactivity. HEK 293T EVs loaded with miR-Comb 15 consistently showed the strongest anti-tumoral activity in vitro and in vivo among the delivery platforms evaluated. Together, these findings identify a functional NFAT3-dependent EV-miRNA program and support EV-mediated delivery of combinatorial miRNA therapeutics as a promising strategy for aggressive cancers.

cancer biology↗

bioRxiv2023

Specific heterotypic interaction promotes asymmetric division of human hematopoietic stem and progenitor cells

Hematopoietic Stem and Progenitor Cells (HSPCs) give rise to all cell types of the hematopoietic system through various processes including asymmetric divisions. However, the contribution of stromal cells of the hematopoietic niches in the control of HSPC asymmetric divisions remains unknown. Using polyacrylamide microwells as minimalist niches, we show that heterotypic interaction with osteoblast promotes asymmetric division of human HSPC. Upon interaction, HSPCs polarize in interphase with centrosome, the Golgi apparatus and lysosomes positioned close to the site of contact. Subsequently during mitosis, HSPCs orient their spindle perpendicular to the plane of contact. This division gives rise to siblings with unequal amounts of lysosomes and differentiation markers such as CD34. Such asymmetric inheritance generates heterogeneity in the progeny, which is likely to be a key contributor to the plasticity of the early steps of hematopoiesis.

cell biology↗

bioRxiv2020

Optimization of cerebrospinal fluid microbial metagenomic sequencing diagnostics

BackgroundInfection in the central nervous system is a severe condition associated with high morbidity and mortality. Despite ample testing, the majority of encephalitis and meningitis cases remain undiagnosed. Metagenomic sequencing of cerebrospinal fluid has emerged as an unbiased approach to identify rare microbes and novel pathogens. However, several major hurdles remains, including establishment of individual limits of detection, removal of false positives and implementation of universal controls. ResultsTwenty-one cerebrospinal fluid samples, in which a known pathogen had been positively identified by available clinical techniques, were subjected to metagenomic DNA sequencing using massive parallel sequencing. Fourteen samples contained minute levels of Epstein-Barr virus. Calculation of the detection threshold for each sample was made using total leukocyte content in the sample and environmental contaminants found in bioinformatic classifiers. Virus sequences were detected in all ten samples, in which more than one read was expected according to calculations. Conversely, no viral reads were detected in seven out of eight samples, in which less than one read was expected according to calculations. False positive pathogens of computational or environmental origin were readily identified, by using a commonly available cell control. For bacteria additional filters including a comparison between classifiers removed the remaining false positives and alleviated pathogen identification. ConclusionsHere we show a generalizable method for detection and identification of pathogen species using metagenomic sequencing. The sensitivity for each sample can be calculated using the leukocyte count and environmental contamination. The choice of bioinformatic method mainly affected the efficiency of pathogen identification, but not the sensitivity of detection. Identification of pathogens require multiple filtering steps including read distribution, sequence diversity and complementary verification of pathogen reads.

microbiology↗

bioRxiv2020

Hematopoietic progenitors polarize in contact with bone marrow stromal cells by engaging CXCR4 receptors.

Hematopoietic stem and progenitor cells (HSPCs) are located in the bone marrow, where they regulate the permanent production and renewal of all blood-cell types. HSPC proliferation and differentiation is locally regulated by their interaction with cells forming specific microenvironments close to the bone matrix or close to blood vessels. However, the cellular mechanisms underlying HSPCs interaction with these cells and their potential impact on HSPC polarity is still poorly understood. Here we modelled the bone-marrow niche using microfluidic technologies in a bone-marrow on a chip device, and evaluated long-duration cell-cell contacts between single HSPCs and stromal cells or endothelial cells in a custom-designed microwell cell-culture system. We found that an HSPC can form a discrete contact site that leads to the extensive polarization of their cytoskeleton architectures. As in the case with immune synapses formed by lymphocytes, the centrosome was located in proximity of the cell-cell contact. The entire microtubule network emanated from the centrosome, and the nucleus was confined to the side opposite of the cell-cell contact. The capacity of the HSPC to polarize appeared specific as it was not observed in contact with skin fibroblasts. The receptors ICAM, VCAM and CXCR4 were identified in the polarizing contact, and were all independently capable of inducing morphological polarization. However, only CXCR4 was independently capable of inducing the polarization of the centrosome-microtubule network. Altogether these results revealed a novel mechanism of HSPC polarization associated with its anchorage to specific cells in the bone-marrow, which might be instrumental in the regulation of their fate.

cell biology↗

bioRxiv2019

Microtubules deform the nucleus and force chromatin reorganization during early differentiation of human hematopoietic stem cells.

Hematopoietic stem cells (HSC) can differentiate into all hematopoietic lineages to support hematopoiesis. Cells from the myeloid and lymphoid lineages fulfill distinct functions with specific shapes and intra-cellular architectures. The role of cytokines in the regulation of HSC differentiation has been intensively studied but our understanding of the potential contribution of inner cell architecture is relatively poor. Here we show that large invaginations are generated by microtubule constraints on the swelling nucleus of human HSCs during early commitment toward the myeloid lineage. These invaginations are associated with chromatin reorganization, local loss of H3K9 trimethylation and changes in expression of specific hematopoietic genes. This establishes the role of microtubules in defining the unique lobulated nuclear shape observed in myeloid progenitor cells and suggests that this shape is important to establish the gene expression profile specific to this hematopoietic lineage. It opens new perspectives on the implications of microtubule-generated forces, in the early specification of the myeloid lineage.

cell biology↗