Biology subjects

Wilmerding, A.

Publications and source records attributed to Wilmerding, A..

3 recordsLinked to original sources

bioRxiv2025

Rootletin Fiber Dynamics Integrate Cytoskeletal Programs to Shape Neuroepithelial Architecture

Central nervous system (CNS) architecture is established early by the organization and proliferative behavior of neuroepithelial (NE) cells, which form a pseudostratified epithelium during neural tube (NT) formation. In neurogenesis, newborn neurons have to detach and exit the neuroepithelium, in a process that requires the coordinated disassembly of apical junctions and the centrosome-cilia module. Although Rootletin--the structural component of the ciliary rootlet and centriolar linker--is classically viewed as a static mechanical element, its behavior in NE cells has not been described in detail. Here, we uncover a conserved, dynamic form of Rootletin fiber organization that remodels in synchrony with NE cell morphogenesis. We show that, in NE cells in interphase, Rootletin fibers extend from the basal body through the apical process toward the nucleus, and that Rootletin maintains its fibrous conformation throughout mitosis. As NE cells initiate apical constriction, Rootletin fibers retract from the apical process and assemble into an anisotropic rim-like structure that aligns with the apical junctional complex. This remodeling is coordinated with microtubule stabilization in low-tension apical endfeet and occurs prior to Lzts1 expression and increased actomyosin contractility. Forced neuronal delamination via Neurogenin-2 or Lzts1 promotes Rootletin rim formation and Rootletin alignment with the apical endfoot cortex. Finally, we show that Zika virus NS5 protein can aberrantly associate with all conformational states of Rootletin fibers, providing a potential mechanical link between ZikaV infection and premature delamination. Together, our findings identify Rootletin as a dynamically regulated cytoskeletal scaffold that orchestrates apical surface remodeling in NE cells and identify a potential mechanism by which ZikaV disrupts neurodevelopment.

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

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↗