Biology subjects

BONNIN, M.-A.

Publications and source records attributed to BONNIN, M.-A..

4 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↗

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

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↗

bioRxiv2019

Mechanical and molecular parameters that influence the tendon differentiation potential of C3H10T1/2 cells in 2D- and 3D-culture systems

One of the main challenges in tendon field relies in the understanding of regulators of the tendon differentiation program. The optimum culture conditions that favor tendon cell differentiation are not identified. Mesenchymal stem cells present the ability to differentiate into multiple lineages in cultures under different cues ranging from chemical treatment to physical constraints. We analyzed the tendon differentiation potential of C3H10T1/2 cells, a murine cell line of mesenchymal stem cells, upon different 2D- and 3D-culture conditions. We observed that C3H10T1/2 cells cultured in 2D conditions on silicone substrate were more prone to tendon differentiation assessed with the expression of the tendon markers Scx, Col1a1 and Tnmd as compared to cells cultured on plastic substrate. 3D fibrin environment was more favorable for Scx and Col1a1 expression compared to 2D-cultures. We also identified TGF{beta}2 as a negative regulator of Tnmd expression in C3H10T1/2 cells in 2D- and 3D-cultures. Altogether, our results provide us with a better understanding of the culture conditions that promote tendon gene expression and identify mechanical and molecular parameters on which we could play to define the optimum culture conditions that favor tenogenic differentiation in mesenchymal stem cells.

developmental biology↗