Biology subjects

DELFINI, M.-C.

Publications and source records attributed to DELFINI, M.-C..

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↗

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↗

bioRxiv2021

HOXB8 counteracts MAPK/ERK oncogenic signaling in a chicken embryo model of neoplasia

HOX transcription factors are members of an evolutionarily conserved family of proteins required for the establishment of the anteroposterior body axis during bilaterian development. Although they are often deregulated in cancers, the molecular mechanisms by which they act as oncogenes or tumor suppressor genes are only partially understood. Since the MAPK/ERK signaling pathway is deregulated in most cancers, we aimed at apprehending if and how Hox proteins interact with ERK oncogenicity. Using an in vivo neoplasia model in the chicken embryo that we have developed, consisting in the overactivation of the ERK1/2 kinases in the trunk neural tube, we analyzed the consequences of HOXB8 gain of function at morphological and transcriptional level in this model. We found that HOXB8 acts as a tumor suppressor, counteracting ERK-induced neoplasia. HOXB8 tumor suppressor function in this model relies on a large reversion of the oncogenic transcriptome induced by ERK. In addition to showing that HOXB8 protein controls the transcriptional responsiveness to ERK oncogenic signaling, our study identified new downstream targets of ERK oncogenic activation in an in vivo context that could provide clues for therapeutic strategies.

cancer biology↗

bioRxiv2021

Sustained experimental activation of FGF8/ERK in the developing chicken spinal cord reproducibly models early events in ERK-mediated tumorigenesis

Most human cancers demonstrate activated MAPK/ERK pathway signaling as a key tumor initiation step, but the immediate steps of further oncogenic progression are poorly understood due to a lack of appropriate models. Spinal cord differentiation follows caudal elongation in vertebrate embryos; both processes are regulated by a FGF8 gradient highest in neuromesodermal progenitors (NMP), where kinase effectors ERK1/2 maintain an undifferentiated state. FGF8/ERK signal attenuation is necessary for NMPs to progress to differentiation. We show that sustained ERK1/2 activity, using a constitutively active form of the kinase MEK1 (MEK1ca) in the chicken embryo, reproducibly provokes neopasia in the developing spinal cord. Transcriptomic data show that neoplasia not only relies on the maintenance of NMP gene expression, and the inhibition of genes expressed in the differentiating spinal cord, but also on a profound change in the transcriptional signature of the spinal cord cells leading to a complete loss of cell-type identity. MEK1ca expression in the developing spinal cord of the chicken embryo is therefore a tractable in vivo model to identify the critical factors fostering malignancy in ERK-induced tumorigenesis.

developmental biology↗