Mounier, C. | bioRxiv Science

bioRxiv2024

Brain-specific Gata4 downregulation in Greywick female mice models the metabolic subtype of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogenous disorder characterized by reproductive and metabolic abnormalities. PCOS etiology remains poorly understood, although the hypothalamus is suspected to play a central role in many cases. Human genetic studies have also shown an association with the transcription factor-coding gene GATA4, but without providing a functional link. Here, we show that adult Greywick female mice may bridge this gap. These mice phenocopy PCOS with partial penetrance, due to serendipitous insertion of a Gata4 promoter-driven transgene in a strong enhancer region. Resulting robust transgene expression in subsets of hypothalamic neurons and glia impairs endogenous Gata4 expression, resulting in misexpression of genes linked to the control of fertility and food intake. We also show that this previously overlooked role of GATA4 in the hypothalamus can be replicated by conditional knockout approaches. Overall, this study sheds light not only on PCOS etiology but also on the role played by GATA4 in the central control of reproduction.

physiology↗

bioRxiv2021

Blockade of pro-fibrotic response mediated by the miR-143/-145 cluster prevents targeted therapy-induced phenotypic plasticity and resistance in melanoma

Lineage dedifferentiation towards a mesenchymal-like state is a common mechanism of adaptive response and resistance to targeted therapy in melanoma. Yet, the transcriptional network driving this phenotypic plasticity remains elusive. Remarkably, this cellular state displays myofibroblast and fibrotic features and escapes MAPK inhibitors (MAPKi) through extracellular matrix (ECM) remodeling activities. Here we show that the anti-fibrotic drug Nintedanib/BIBF1120 is active to normalize the fibrous ECM network, enhance the efficacy of MAPK-targeted therapy and delay tumor relapse in a pre-clinical model of melanoma. We also uncovered the molecular networks that regulate the acquisition of this resistant phenotype and its reversion by Nintedanib, pointing the miR-143/-145 pro-fibrotic cluster as a driver of the therapy-resistant mesenchymal-like phenotype. Upregulation of the miR-143/-145 cluster under BRAFi/MAPKi therapy was observed in melanoma cells in vitro and in vivo and was associated with an invasive/undifferentiated profile of resistant cells. The 2 mature miRNAs generated from this cluster, miR-143-3p and miR-145-5p collaborated to mediate phenotypic transition towards a drug resistant undifferentiated mesenchymal-like state by targeting Fascin actin-bundling protein 1 (FSCN1), modulating the dynamic crosstalk between the actin cytoskeleton and the ECM through the regulation of focal adhesion dynamics as well as contributing to a fine-tuning of mechanotransduction pathways. Our study brings insights into a novel miRNA-mediated regulatory network that contributes to non-genetic adaptive drug resistance and provides proof-of-principle that preventing MAPKi-induced pro-fibrotic stromal response is a viable therapeutic opportunity for patients on targeted therapy.

cancer biology↗