Laplante, M. | Search bioRxiv

bioRxiv2026

ZNF768 regulates expression of E2F1 protein to drive G0/G1 transition and cell cycle progression.

Accurate and tightly coordinated cell cycle progression and cell proliferation are critical for development, growth and homeostasis of an organism. Recently, Zinc finger protein 768 (ZNF768) was identified as a transcription factor driving cellular proliferation, in both a p53-dependent and independent manner. ZNF768 interacts with and represses p53 functions to limit cell cycle delay. Independently, ZNF768 promotes the transcription of key regulators of the cell cycle machinery, although the mechanisms through which this occurs remain unknown. Here, we report that ZNF768 protein levels are tightly regulated during the cell cycle, and its depletion leads to cell cycle exit and induction of quiescence. We found that ZNF768 modulates the cell cycle, at least in part, by controlling expression of the major pro-proliferative transcription factor E2F1 independently of p53 activation. Consequently, depletion of ZNF768, which also represses expression of the key mitotic transcription factor and E2F1 target FOXM1, leads to numerous mitotic errors. Supporting these findings, cancer genomics analyses reveal that ZNF768 expression levels are positively associated with E2F1 and FOXM1 expression levels in human tumors, suggesting that cancer cells might use ZNF768 to override cell cycle arrest, sustain proliferation, and promote cancer progression. Altogether, our results reveal that ZNF768 modulates cell cycle entry and proliferation, at least in part by regulating E2F1 expression.

cell biology↗

bioRxiv2026

An Itch Receptor Drives Melanoma

Mas-Related GPCR X4 (MRGPRX4) is a sensory neuron-restricted receptor for cholestatic itch. Here, we identify MRGPRX4 as an unexpected melanoma driver. MRGPRX4 is upregulated in melanoma and is confined to invasive, neural-crest-like and pre-EMT states associated with dedifferentiation and therapy resistance. Ectopic MRGPRX4 expression in mouse melanocytes drives 100% penetrant, highly metastatic melanoma, demonstrating oncogenic behavior. MRGPRX4 promotes melanoma cell proliferation and invasion through basal, ligand-independent, PI3K-AKT-MAPK activation. Multi-omics links MRGPRX4 expression to a mesenchymal/neural-crest-like program that defines a distinct invasive MRGPRX4? niche. Comparing transcptomics of MRGPRX4-driven tumors shows a broad overlap with BRAF/NRAS-driven tumors; however, the MRGPRX4 model also enriches an ECM-rich, invasive neural crest-like melanoma state. MRGPRX4 further remodels the tumor microenvironment toward an immunosuppressive, checkpoint-high state enriched in suppressive myeloid cells. Pharmacologic MRGPRX4 inhibition suppresses basal signaling and limits melanoma growth and invasion. In sum, melanoma exploits MRGPRX4 to acquire an invasive and immunosuppressive phenotype, nominating this somatosensory GPCR as a promising therapeutic target.

cancer biology↗

bioRxiv2021

Fast transcriptional activation of developmental signalling pathways during wound healing of the calcareous sponge Sycon ciliatum

BackgroundThe ability to regenerate lost or damaged body parts is an ancient animal characteristic with a wide yet variable distribution across all phyla. Sponges, likely the sister group to all other animals, have remarkable regenerative abilities including whole body regeneration and re-development from dissociated cells. The calcareous sponge Sycon ciliatum has been subject to various regeneration studies since the beginning of the last century. However, the early steps of wound healing of S. ciliatum have not been addressed from the molecular perspective. ResultsIn this study, we combined electron microscopy with gene expression analysis to investigate wound healing after transverse sectioning of S. ciliatum. Microscopic analysis revealed massive transdifferentiation and collective migration behaviour of choanocytes and pinacocytes early upon injury (6-12h) as the main mechanisms for quick closure of the wound surface. RNA-sequencing identified upregulation of components of the conserved metazoan Wnt and TGF{beta} signalling pathways within 3h, preceding morphologically detectable wound healing events. De novo upregulation after a decline in expression coincides with morphologically visible polarity establishment. Moreover, by integrating the new wound healing data set with previously published data derived from intact sponge, we demonstrate similarity between gene activity during early wound healing and osculum maintenance. Whole mount in situ hybridisation of the TGF{beta} signalling pathway ligand SciTGF{beta}U and signal transducer SciSmadRa show that the early activation of both is initially encompassing a large area surrounding the cut surface with gradual restriction to the edge of the forming regenerative membrane as wound healing progresses. While SciTGF{beta}U transcripts are localised to exo- and endopinacocytes, SciSmadRa expression appears across all cell types. Using an EdU cell proliferation assay, we found that a global increase in cell proliferation is not visible before 12h into wound healing. Hence, the initial stages to cover the injury site including cell transdifferentiation and migration seem to be executed by cells remaining after injury. Gene expression clustering coupled with GO term enrichment analysis confirmed that expression of genes involved in processes related to cell proliferation, DNA repair as well as apoptotic processes at 3 and 6h of wound healing was not upregulated. On the other hand, genes associated with positive regulation of transcription, signal transduction, actin filament and chromatin organisation, as well as the Wnt signalling pathway are upregulated at early wound healing stages. ConclusionWe have analysed wound healing in the calcareous sponge Sycon ciliatum using microscopic and genomic methods. This study highlights a remarkable mechanism of interplay between cell transdifferentiation and collective migration we hypothesise to be regulated by conserved metazoan developmental pathways and numerous taxonomically restricted genes. Expression of these genes in regenerating and intact sponges sheds light on the long-standing question whether embryonic developmental pathways are redeployed in regeneration.

developmental biology↗