Biology subjects

Gourain, V.

Publications and source records attributed to Gourain, V..

5 recordsLinked to original sources

bioRxiv2022

Targeting the BAG-1 family of co-chaperones in lethal prostate cancer.

Therapies that abrogate persistent androgen receptor (AR) signaling in castration resistant prostate cancer (CRPC) remain an unmet clinical need. The N-terminal domain (NTD) of the AR drives transcriptional activity in CRPC but is intrinsically disordered and remains a challenging therapeutic target. Therefore, inhibiting critical co-chaperones, such as BAG-1L, is an attractive alternative strategy. We performed druggability analyses demonstrating the BAG domain to be a challenging drug target. Thio-2, a tool compound, has been reported to bind the BAG domain of BAG-1L and inhibit BAG-1L-mediated AR transactivation. However, despite these data, the mechanism of action of Thio-2 is poorly understood and the BAG domain which is present in all BAG-1 isoforms has not been validated as a therapeutic target. Herein, we demonstrate growth inhibiting activity of Thio-2 in CRPC cell lines and patient derived models with decreased AR genomic binding and AR signaling independent of BAG-1 isoform function. Furthermore, genomic abrogation of BAG-1 isoforms did not recapitulate the described Thio-2 phenotype, and NMR studies suggest that Thio-2 may bind the AR NTD, uncovering a potential alternative mechanism of action, although in the context of low compound solubility. Furthermore, BAG-1 isoform knockout mice are viable and fertile, in contrast to previous studies, and when crossed with prostate cancer mouse models, BAG-1 deletion does not significantly impact prostate cancer development and growth. Overall, these data demonstrate that Thio-2 inhibits AR signaling and growth in CRPC independent of BAG-1 isoforms, and unlike previous studies of the activated AR, therapeutic targeting of the BAG domain requires further validation before being considered a therapeutic strategy for the treatment of CRPC.

molecular biology↗

bioRxiv2021

CD4+ and CD8+ regulatory T cells characterization in the rat using a unique transgenic Foxp3-EGFP model.

BackgroundCD4+ and CD8+ regulatory T cells (Treg) in diverse species include different subsets from different origins. In all species, CD8+ Treg have been poorly characterized. CD4+ and CD8+ Treg in rats have only partially been characterized and there is no rat model in which FOXP3+ Treg are genetically tagged. ResultsWe generated a rat transgenic line using the CRISPR/Cas9 system in which EGFP was inserted in frame on the 3 end of the Foxp3 gene using a 2A self-cleaving peptide. EGFP was exclusively expressed by CD4+ and CD8+ T cells in similar proportion as observed with anti-FOXP3 antibodies. CD4+EGFP+ Treg were 5-10 times more frequent than CD8+EGFP+ Treg. CD4+ and CD8+ EGFP+ Treg expressed both the CD25highCD127lowCD45RClow/- markers. The suppressive activity of CD4+ and CD8+ Treg was largely confined to EGFP+ cells. RNAseq analyses showed similarities but also differences among CD4+ and CD8+ EGFP+ cells and provided the first description of the natural FOXP3+ CD8+ Treg transcriptome. In vitro culture of CD4+ and CD8+ EGFP- cells with TGFbeta and IL-2 resulted in the induction of EGFP+ Treg. Preferential expansion of CD4+ and CD8+ EGFP+ Treg could be detected upon in vivo administration of a low dose of IL-2. ConclusionsThis new and unique Foxp3-EGFP rat line constitutes a useful model to identify and isolate viable natural and induced CD4+ and CD8+ Treg. Additionally, it allows to identify new molecules expressed in CD8+ Treg that may allow to better define their phenotype and function not only in rats but also in other species.

immunology↗

bioRxiv2020

Multi-dimensional transcriptome analysis reveals modulation of cholesterol metabolism as highly integrated response to brain injury.

BackgroundZebrafish is an attractive model to investigate regeneration of the nervous system. Despite major progress in our understanding of the underlying processes, the transcriptomic changes are largely unknown. We analysed the transcriptome of the regenerating telencephalon for changes in the expression of mRNAs, their splice variants and investigated the putative role of regulatory RNAs in the modulation of these transcriptional changes. ResultsProfound changes in the expression of genes and their splice variants engaged in many distinct processes were observed. As exemplified by the coordinated regulation of the cholesterol synthesizing enzymes and transporters, the genome responded to injury of the telencephalon in a multi-tiered manner with distinct and interwoven changes in expression of enzymes, transporters and their regulatory molecules. This coordinated genomic response involved a decrease of the mRNA of the key transcription factor SREBF2, induction of microRNAs (miR- 182, miR-155, miR-146, miR-31) targeting cholesterol genes, shifts in abundance of splice variants as well as regulation of long non-coding RNAs. ConclusionsDifferential transcription and splicing are important processes in response to injury of the telencephalon. Cholesterol metabolism is switched from synthesis to relocation of cholesterol. Based on our in silico analysis, this switch involves complementary and synergistic inputs by different regulatory principles. Our studies suggest that adaptation of cholesterol metabolism appears to be a key process involved in regeneration of the injured zebrafish brain.

bioinformatics↗

bioRxiv2019

BMP signaling regulates Id1 mediated neural stem cell quiescence in the adult zebrafish brain via a phylogenetically conserved enhancer module

In the telencephalon of adult zebrafish, the inhibitor of DNA binding 1 (id1) gene is expressed in radial glial cells (RGCs), behaving as neural stem cells (NSCs), during constitutive and regenerative neurogenesis. Id1 controls the balance between resting and proliferating states of RGCs by promoting quiescence. Here, we identified a phylogenetically conserved cis-regulatory module (CRM) mediating the specific expression of id1 in RGCs. Systematic deletion mapping and mutation of conserved transcription factor binding sites in stable transgenic zebrafish lines reveal that this CRM operates via conserved smad1/5 and 4 binding motifs (SBMs) under both homeostatic and regenerative conditions. Transcriptome analysis of injured and uninjured telencephala as well as pharmacological inhibition experiments identify a crucial role of bone morphogenetic protein (BMP) signaling for the function of the CRM. Our data highlight that BMP signals control id1 expression and thus NSC proliferation during constitutive and induced neurogenesis.

developmental biology↗

bioRxiv2018

Pcdh18a-positive tip cells instruct notochord formation in zebrafish

The notochord defines the axial structure of all vertebrates during development. Notogenesis is a result of major cell reorganization in the mesoderm, the convergence and the extension of the axial cells. However, it is currently not known how these processes act together in a coordinated way during notochord formation. Analysing the tissue flow, we determined the displacement of the axial mesoderm and identified, relative to the ectoderm, an actively-migrating notochord tip cell population and a group of trailing notochordal plate cells. Molecularly, these tip cells express Protocadherin18a, a member of the cadherin superfamily. We show that Pcdh18a-mediated recycling of E-cadherin adhesion complexes transforms these tip cells into a cohesive and fast migrating cell group. In turn, these tip cells subsequently instruct the trailing mesoderm. We simulated cell migration during early mesoderm formation using a lattice-based mathematical framework, and predicted that the requirement for an anterior, local motile cell cluster could guide the intercalation of the posterior, axial cells. Indeed, grafting experiments validated the predictions and induced ectopic notochord-like rods. Our findings indicate that the tip cells influence the trailing mesodermal cell sheet by inducing the formation of the notochord.

developmental biology↗