Biology subjects

Artus, J.

Publications and source records attributed to Artus, J..

6 recordsLinked to original sources

bioRxiv2025

Single-cell omics reveal distinct gene regulatory dynamics underpinning embryonic and extraembryonic lineage functions during pig blastocyst development

The late-stage development of the blastocyst before implantation is a unique feature of ungulates. During this period, the epiblast proliferates and remains pluripotent for several days before gastrulation begins. Simultaneously, extra-embryonic tissues undergo significant growth, elongating to several tens of centimeters. However, the mechanisms that regulate and synchronize these processes remain poorly understood. In this study, we analyzed transcriptomic and epigenomic data at the single-cell level from early and late porcine blastocyst cells, spanning from the hatched blastocyst stage (E7) to early (E9) and late ovoid blastocyst (E11). We characterized 15,370 blastocyst cells, clustering them into distinct embryonic and extra-embryonic populations with specific chromatin accessibility landscapes. For each population, we inferred gene regulatory networks based on enhancer-driven gene regulation modules (eRegulons) and validated them through motif occupancy visualization. Our findings reveal strong dynamics in gene regulatory module activity within extra-embryonic tissues at the onset of blastocyst elongation, while gene regulatory activity in the epiblast remains relatively stable.

developmental biology↗

bioRxiv2024

Donor embryonic stem cells impede host epiblast specification in 8-cell stage chimeras by crowding and FGF4 signalling

During mouse embryo compaction, outer cells become trophectoderm, while inner cells form the inner cell mass (ICM), later differentiating into primitive endoderm and epiblast - source of embryonic stem cells (ESCs) - during blastocyst formation. Trophectoderm specification is driven by position-governed polarisation, while primitive endoderm specification is positively regulated by FGF4 signalling from the ICM and epiblast. When injected into an 8-cell stage morula, ESCs can exclude host cells from the epiblast, leading to mice derived entirely from these cells. While evidence suggests roles for ESC-produced FGF4 and physical crowding in host cell displacement from the ICM, the interplay between these possible mechanisms has yet to be dissected, in part due to the lack of studies using Fgf4-/- ESCs. Here, we combine chimaera titration assays with mathematical modelling to study these mechanisms of host cell displacement. Both Fgf4+/+ and Fgf4-/- ESCs displaced host cells from the epiblast, while only Fgf4-/- injected embryos reduced primitive endoderm and increased trophectoderm, indicating sequential exclusion by displacement crowding followed by FGF4 signalling. SUMMARY STATEMENTIn mouse blastocyst chimeras, donor cells displace host cells from the epiblast by a combination of crowding and FGF4 signalling.

developmental biology↗

bioRxiv2023

Cell specification and functional interactions in the pig blastocyst inferred from single cell transcriptomics

The early embryonic development of the pig comprises a long in utero pre- and peri-implantation development, which dramatically differs from mouse and human. During this pro-tracted peri-implantation period, an intimate dialogue between the embryo and the uterus is established through a complex series of paracrine signals. It leads to concomitant drastic changes in the embryonic morphology and uterine receptivity to implantation. From day 7 after fertilization, the spherical blastocyst elongates as ovoid, tubular and filamentous wich transforms from a 0.5-1 mm diameter sphere to a 1000 mm long filamentous blastocyst at day 16. At the same time, the inner cell mass moves up to the trophoblast as the Raubers layer disappears and evolves as an embryonic disc that is directly exposed to molecules present in the uterine fluids. These drastic changes occurring before implantation are driven and coordinated by interactions between embryonic cells and maternal tissues. To better understand the biology of pig embryos before implantation, we generated a large dataset of single-cell RNAseq at different embryonic stages (early and hatched blastocyst, spheroid and ovoid conceptus) and proteomic datasets from corresponding uterine fluids. These data were cleaned, filtered and represent a total of 34,888 cells. We first characterised the embryonic and extra-embryonic cell populations and their evolution, and identified population-specific markers of the three main populations (epiblast, trophectoderm and hypoblast). Our analysis also confirmed known functions and predicted new biological functions associated with these cell populations.We then inferred gene regulatory networks working on modules of gene regulation (regulon) and selected those that were specifically active in each embryonic population. We confirmed the relevance of the identified regulons by a meta-analysis of two other scRNAseq datasets (porcine and human preimplantation embryos). We then linked these regulons to signalling pathways and biological processes. Our results confirm the molecular specificity and functionality of the three main cell populations and identify novel stage-specific subpopulations. In particular, we discovered two previously unknown subpopulations of the trophectoderm, one characterised by the expression of LRP2, which could represent a subpopulation of progenitor cells, and the other, expressing many pro-apoptotic markers, which could correspond to the cells of the Raubers layer. We also provide new insights into the biology of these populations, their reciprocal functional interactions and the molecular dialogue established with the maternal uterine environment.

developmental biology↗

bioRxiv2023

BCR-ABL promotes hematopoietic stem and progenitor cell formation in embryonic stem cells

Generating Hematopoietic Stem Cells (HSCs) from Pluripotent Stem Cells (PSCs) has been a long-lasting quest in the field of hematopoiesis. Previous studies suggested that enforced expression of BCR-ABL, the unique oncogenic driver of Chronic Myelogeneous Leukemia (CML), in Embryonic Stem Cells (ESCs)-derived hematopoietic cells is sufficient to confer long-term in vivo repopulating potential. To precisely uncover the molecular events regulated by the Tyrosine-kinase activity of BCR-ABL1 (p210) during the course of hematopoietic differentiation, we engineered a Tet-ON inducible system to modulate its expression in murine ESC. We showed in unique site-directed knock-in ESC model, that BCR-ABL expression tightly regulated by doxycycline (dox) controls the formation and the maintenance of immature hematopoietic progenitors. Interestingly, these progenitors can be expanded in vitro for several passages in the presence of dox. Our analysis of cell surface markers and transcriptome compared to wild-type fetal and adult HSCs unraveled a similar molecular signature. LTC-IC assay confirmed their self-renewal capacities albeit with a differentiation bias towards erythroid and myeloid cells. Collectively, our novel Tet-ON system represents a unique in vitro model to shed lights on ESC-derived hematopoiesis, CML initiation and maintenance. KEY POINTSO_LIWe report a unique BCR-ABL-induced-embryonic stem cell -derived hematopoiesis model in murine embryonic stem cells C_LIO_LIThis BCR-ABL-induced self-renewal and differentiation model can be of major interest to uncover molecular events required for ESC-derived hematopoiesis C_LI

cancer biology↗

bioRxiv2022

miR-495-3p Sensitizes BCR::ABL1 Expressing Leukemic cells to Tyrosine Kinase Inhibitors by Targeting Multidrug Resistance 1 Gene including in T315I Mutated cells

Chronic myeloid leukemia (CML) is a clonal hematopoietic malignancy driven by the BCR::ABL1 fusion oncoprotein. The development of tyrosine kinase inhibitors (TKIs) has deeply increased long-term survival of CML patients. Nonetheless, one patient out of four will switch TKI off owing either to drug intolerance or resistance partly due to amplification or mutations of BCR::ABL1 oncogene and alteration of ATP-binding cassette (ABC) transporters. Increasing evidence suggests an involvement of the microRNA miR-495-3p in cancer-associated chemo-resistance through multidrug resistance 1 (MDR1) gene which encodes an ATP-dependent efflux pump. Our study aimed at investigating the potential role of miR-495-3p in CML TKI chemo-sensitivity and determining the underlying molecular circuitry involved. We first observed that miR-495-3p expression was lower in BCR::ABL1 expressing cellular models in vitro. Notably, loss-of-function experiments showed increased proliferation associated with a decreased number of non-dividing cells (G0/G1) and resistance to Imatinib. Conversely, our data showed that miR-495-3p overexpression hindered leukemic cell growth and TKI resistance even in Imatinib-resistant T315I-mutant cells as well as drug efflux activity through MDR1 regulation. To further investigate the role of miR-495-3p in CML patients, we found that predicted miR-495-3p targets were upregulated in patients in blast crisis involved in protein phosphorylation and associated with the worst prognosis. Taken together, our results demonstrate that down-regulation of miR-495-3p expression is important in the malignant phenotype of CML and TKI resistance mechanisms, which could be a useful biomarker and a potential therapeutic target to eradicate CML. MeSH termsO_LIATP Binding Cassette Transporter, Subfamily B C_LIO_LIATP Binding Cassette Transporter, Subfamily B, Member 1 / drug effects C_LIO_LIATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism* C_LIO_LIBlast Crisis / pathology C_LIO_LICell Line, Tumor C_LIO_LICell Proliferation / drug effects* C_LIO_LICell Survival / drug effects C_LIO_LIDrug Resistance C_LIO_LIGenes, MDR C_LIO_LIImatinib Mesylate C_LIO_LILeukemia, Myelogenous, Chronic, BCR-ABL Positive C_LIO_LIMicroRNAs / genetics C_LIO_LIMicroRNAs / physiology* C_LI HIGHLIGHTSO_LImiR-495-3p inhibits leukemic cell growth and is downregulated in BCR::ABL1 expressing cell lines C_LIO_LImiR-495-3p modulates response to TKI treatment including in UT7 cells expressing T315I C_LIO_LIOverexpression of miR-495-3p leads to a decrease of MDR1 and drug efflux activity C_LIO_LIBioinformatics analyses reveal that MiR-495-3p target genes are upregulated in blast crisis C_LI

cancer biology↗

bioRxiv2017

ICM conversion to epiblast by FGF/ERK inhibition is limited in time and requires transcription and protein degradation

Abbreviations used in this study\n\nAbstractInner cell Mass (ICM) specification into epiblast (Epi) and primitive endoderm (PrE) is an asynchronous and progressive process taking place between E3.0 to E3.75 under the control of the FGF/ERK signaling pathway. Here, we have analyzed in details the kinetics of specification and found that ICM cell responsiveness to the up and down regulation of FGF signaling activity are temporally distinct. We also showed that PrE progenitors are generated later than Epi progenitors. We further demonstrated that, during this late phase of specification, a 4 hours period of FGF/ERK inhibition prior E3.75 is sufficient to convert ICM cells into Epi. Finally, we showed that ICM conversion into Epi in response to inhibition during this short time window requires both transcription and proteasome degradation. Collectively, our data give new insights into the timing and mechanisms involved in the process of ICM specification.

developmental biology↗