Biology subjects

DUPREZ, D.

Publications and source records attributed to DUPREZ, D..

8 recordsLinked to original sources

bioRxiv2026

Regionalisation of muscle nucleus heterogeneity in foetal skeletal muscle

Skeletal muscle is organized into functional domains with attachments at both extremities to tendons via the myotendinous junction (MTJ) and innervation in the middle via the neuromuscular junction (NMJ). In adult muscle, the molecular heterogeneity of muscle domains is described at the level of myonuclei with specialized MTJ and NMJ myonuclei at the tips and middle of muscle fibre. However, how molecular heterogeneity emerges during development remains poorly understood. Combining single-cell and single-nucleus RNA sequencing approaches with in situ hybridization experiments to limb muscles of chicken embryos, we uncover transcriptionally distinct muscle nuclei according to tip and central domains, both in myofibres and in mononucleated myogenic cells. At early foetal stage, all myonuclei display either a tip or a central domain identity. Immature mononucleated myogenic cells are enriched in the tip domain. Tip myonuclei of foetal muscles show a robust transcriptional signal transduction signature, which highlights molecular crosstalks between tip myonuclei and adjacent tendon fibroblasts but also with the adjacent immature mononucleated myogenic cells. We propose that the tip muscle domain is a signalling centre interacting with tendon fibroblasts to regulate muscle/tendon attachment and with adjacent mononucleated muscle cells to regulate myogenesis in limb foetal muscles.

developmental biology↗

bioRxiv2025

RIPOR2 promotes multinucleation of melanoma cells downstream of the RAS/ERK oncogenic pathway

One-third of skin melanomas arise from melanocytic nevi, benign skin lesions composed of clustered melanocytes. Benign nevi are associated with overactivation of the mitogen-activated protein kinase RAS/ERK pathway, resulting from driver mutations, most commonly in the BRAF or NRAS gene. However, this overactivation in melanocytes is insufficient to induce melanoma formation, as only a minority of benign nevi give rise to melanoma. Overactivation of the RAS/ERK pathway promotes genetic and epigenetic alterations by inducing aneuploidy, but the processes by which nevi evolve into melanoma via RAS/ERK pathway-dependent aneuploidy are only partially understood. Using single-nucleus RNA sequencing after overactivation of the RAS/ERK pathway in the chicken embryo, we discovered that RIPOR2 is a positive transcriptional target of this pathway, including in melanocyte precursors. Similar transcriptional control of RIPOR2 by RAS/ERK is conserved in human melanoma cells. RIPOR2 emerged as an attractive target because it encodes an atypical RHOA inhibitory protein involved in the development of physiologically multinucleated cell types. Multinucleation in cancer has been shown to promote aneuploidy, which correlates with tumor aggressiveness. We found that RIPOR2 is ectopically expressed in human nevi and skin melanomas and functionally promotes multinucleation in both an animal model and human tumor-derived cells, including melanoma cell lines. Our results suggest that RIPOR2 expression, downstream of RAS/ERK overactivation in skin melanocytes, promotes the emergence of multinucleated cells, a previously overlooked step in melanoma formation.

cancer biology↗

bioRxiv2024

Spatial and mechanical environments regulate the heterogeneity of myonuclei

Skeletal muscle formation involves tight interactions between muscle cells and associated connective tissue fibroblasts. Every muscle displays the same type of organisation, they are innervated in the middle and attached at both extremities to tendons. Myonuclei are heterogeneous along myotubes and regionalised according to these middle and tip domains. During development, as soon as myotubes are formed, myonuclei at muscle tips facing developing tendons display their own molecular program. In addition to molecular heterogeneity, a subset of tip myonuclei has a fibroblastic origin different to the classical somitic origin, highlighting a cellular heterogeneity of myonuclei in foetal myotubes. To gain insights on the functional relevance of myonucleus heterogeneity during limb development, we used 2D culture and co-culture systems to dissociate autonomous processes (occurring in 2D-cultures) from 3D-spatial environment of tissue development. We also assessed the role of mechanical parameters in myonucleus heterogeneity in paralysed limb muscles. The regionalisation of cellular heterogeneity was lost in 2D cell culture systems and paralyzed muscles. The molecular signature of MTJ myonuclei was also lost a dish and paralysed muscles indicating a requirement of spatial and mechanical input for MTJ formation. Tip genes that maintain their expression in a dish are involved in myofibrillogenesis and myotube attachments. The behaviour of regionalized markers in cultured myotubes and paralyzed muscles allows us to deduce whether the genes intervene in myogenesis, myotube attachment or MTJ formation. HighlightsThe regionalisation of cellular heterogeneity of myonuclei is lost in cultured myotubes BMP signalling regulates fibroblast nucleus incorporation into cultured myotubes The molecular signature of MTJ myonuclei is lost in cultured myotubes and paralysed muscles Tip genes involved in myofibrillogenesis maintain their regionalised expression in cultured myotubes

developmental biology↗

bioRxiv2024

Human adipose stromal cells differentiate towards a tendon phenotype with extracellular matrix production and adapted visco-elastic properties in a 3D-culture system

Tendon cell differentiation relies on molecular and mechanical parameters that control the expression of tendon-associated transcription factors and extracellular matrix proteins. However, the minimal cues able to initiate tendon differentiation from progenitor cells remains unknown. We analysed the tendon differentiation program in human adipose stromal cells (hASCs) cultured in a minimal 3D-system. We generated 3D-hASC constructs by embedding hASCs in a type-I collagen gel under a static uniaxial geometrical constraint with no additional molecular and mechanical cues, and assessed tendon-associated gene expression and mechanical properties for up to three weeks in culture. Analysis of tendon-associated genes revealed a molecular progression consistent with the acquisition of a tendon phenotype. The analysis of viscoelastic properties of 3D-hASC constructs by nano-indentation indicated a progressive increase in tissue stiffness up to 10 kPa, concomitant with a reduced stress relaxation indicative of solid-like mechanical properties. These changes in mechanical properties parallel the molecular change of matrix genes during the time of cultures. In summary, we have established that hASCs cultured in a minimal 3D-system progress into the tendon differentiation program associated with variations of mechanical properties.

developmental biology↗

bioRxiv2024

Limb connective tissue is organized in a continuum of promiscuous fibroblast identities during development

Tight developmental coordination of muscle attachments with skeletal muscle is fundamental for building functional limbs and allowing locomotion. Muscle attachments include connective tissue fibroblasts of tendon and muscle connective tissue. Although muscle attachments play critical roles in development, our understanding of connective tissue fibroblast developmental programs lags behind that of other components of the musculoskeletal system, mainly because fibroblasts are highly heterogeneous and poorly characterized. Combining single-cell RNA-sequencing-based strategies including trajectory inference and in situ hybridization analyses, we address the diversity of connective tissue fibroblasts and their developmental trajectories during chicken limb fetal development. We show that fibroblasts switch from a program providing positional information to a program of lineage diversification at the onset of fetal period. Muscle connective tissue and tendon contain several fibroblast populations that emerge asynchronously. Once the final muscle pattern is set, in silico fibroblast populations that are close in transcriptional identity are found in neighbouring locations in limbs, prefiguring the adult fibroblast layers associated to muscle. We propose that the limb connective tissue is organised in a continuum of promiscuous fibroblast identities, allowing for the robust and efficient connection of the muscular system to bone and skin. HighlightsDissection of connective tissue heterogeneity using single-cell RNA-sequencing and in situ RNA staining In silico fibroblast populations map to distinct fibroblast layers in limbs Molecular signatures of fetal fibroblast populations at the origin of limb adult connective tissue Epimysium and endomysium fibroblasts are transcriptionally distinct at fetal stage Limb fibroblasts display promiscuous identities reflecting their interconnected 3D-network Fibroblasts switch from providing positional information to differentiation during development

developmental biology↗

bioRxiv2020

BMP signalling directs a fibroblast-to-myoblast conversion at the connective tissue/muscle interface to pattern limb muscles

Positional information driving limb muscle patterning is contained in lateral plate mesoderm-derived tissues, such as tendon or muscle connective tissue but not in myogenic cells themselves. The long-standing consensus is that myogenic cells originate from the somitic mesoderm, while connective tissue fibroblasts originate from the lateral plate mesoderm. We challenged this model using cell and genetic lineage tracing experiments in birds and mice, respectively, and identified a subpopulation of myogenic cells at the muscle tips close to tendons originating from the lateral plate mesoderm and derived from connective tissue gene lineages. Analysis of single-cell RNA-sequencing data obtained from limb cells at successive developmental stages revealed a subpopulation of cells displaying a dual muscle and connective tissue signature, in addition to independent muscle and connective tissue populations. Active BMP signalling was detected in this junctional cell sub-population and at the tendon/muscle interface in developing limbs. BMP gain- and loss-of-function experiments performed in vivo and in vitro showed that this signalling pathway regulated a fibroblast-to-myoblast conversion. We propose that localised BMP signalling converts a subset of lateral plate mesoderm-derived fibroblasts to a myogenic fate and establishes a boundary of fibroblast-derived myonuclei at the muscle/tendon interface to control the muscle pattern during limb development.

developmental biology↗

bioRxiv2020

Egr1 loss-of-function promotes beige adipocyte differentiation and activation specifically in inguinal subcutaneous white adipose tissue

Exercise, cold exposure and fasting lead to the differentiation of inducible-brown adipocytes, called beige adipocytes, within white adipose tissue and have beneficial effects on fat burning and metabolism, through heat production. This browning process is associated with an increased expression of the key thermogenic mitochondrial uncoupling protein 1, Ucp1. Egr1 transcription factor has been described as a regulator of white and beige differentiation programs, and Egr1 depletion is associated with a spontaneous increase of subcutaneous white adipose tissue browning, in absence of external stimulation. Here, we demonstrate that Egr1 mutant mice exhibit a restrained Ucp1 expression specifically increased in subcutaneous fat, resulting in a metabolic shift to a more brown-like, oxidative metabolism, which was not observed in other fat depots. In addition, Egr1 is necessary and sufficient to promote white and alter beige adipocyte differentiation of mouse stem cells. These results suggest that modulation of Egr1 expression could represent a promising therapeutic strategy to increase energy expenditure and to restrain obesity-associated metabolic disorders.

developmental biology↗

bioRxiv2020

NOTCH inhibition promotes myoblast fusion by releasing HEYL repression on TMEM8C regulatory regions in foetal skeletal muscles

Differentiation and fusion are two intricate processes involved in skeletal muscle development. The close association of differentiation and fusion makes it difficult to address the process of fusion independently of differentiation. Using the fusion marker myomaker, named TMEM8C in chicken, we found that both TMEM8C transcripts and the differentiated and fusion-competent MYOG+ cells are preferentially regionalized in the central regions of limb foetal muscles in chicken embryos. Because the NOTCH signalling pathway is a potent inhibitor of muscle differentiation during developmental myogenesis, NOTCH function in myoblast fusion was not addressed so far. We analysed the consequences of NOTCH inhibition for myoblast fusion and TMEM8C expression during foetal myogenesis using in vitro and in vivo chicken systems. NOTCH inhibition following chicken embryo immobilisation or in myoblast cultures increased TMEM8C expression and myoblast fusion. Moreover, we showed that NOTCH inhibition induced the un-binding of the HEYL transcriptional repressor from the TMEM8C regulatory regions in limb muscles and myoblast cultures. These results identify a molecular mechanism underlying the fusion-promoting effect of NOTCH-inhibition during foetal myogenesis.

developmental biology↗