Project description:In the heart development, mesodermal progenitor cells in pharyngeal apparatus, termed cardiopharyngeal mesoderm, contribute to both atruim and right ventricle. Tbx1 gene, encoding a T-box transctiption factor and gene haploinsufficient in 22q11.2 deletion syndrome, is required for cardiac outflow tranct and branchiomeric muscle development. To understand how TBX1 affect open chromatin status in cardiopharyngeal mesoderm, we performed ATAC-seq in Tbx1-Cre lineage with/without Tbx1 expression.
Project description:We have developed a protocol to generate cardiopharyngeal mesoderm (CPM) in vitro by Mesp1 induction in ES cells. The goal of this study is to compare the transcriptome of CPM-derived cardiac and skeletal myogenic progenitors to identify novel lineage-specific markers. mRNA profiles of CPM-derived D6 (early) and D12 (late), cardiac (BMP) and skeletal myogenic (control) progenitors were generated
Project description:We used the assay for transposon-accessible chromatin using sequencing (ATAC-seq) on FACS-purified cells to profile chromatin accessibility during early cardiopharyngeal fate choices in Ciona. We obtained ~500 million unique reads from samples comprising cardiopharyngeal mesoderm and mesenchymal cells, as well as whole Ciona embryos and genomic DNA control. We combined ATAC-seq peaks from all the replicates to generate an atlas of 56,090 unique and non-overlapping accessible regions (accessome) covering 9.25% of the C. robusta genome. We used the accessome to analyze differential accessibility and integrated expression data to compare the chromatin and gene expression dynamics underlying cardiopharyngeal fate specification. In summary, we revealed that most changes in accessibility occur upon induction of multipotent cardiopharyngeal progenitors from the founder cells. Comparing differential expression to differential accessibility shows that genes activated in the multipotent progenitors tend to have regions that specifically open nearby them. We found that the elements accessible specifically in multipotent cardiopharyngeal progenitors were enriched in Fox, GATA and nuclear receptor binding motifs. CRISPR-mediated loss of Foxf function followed by FACS, ATAC-seq and RNA-seq showed that Foxf is required to open ~22% of the cardiopharyngeal-specific elements. Notably, elements associated with de novo expressed genes, which turn on either in heart or pharyngeal muscle progenitors, were also opening in multipotent progenitors, whereas only ~10% of differentially expressed genes had differentially accessible elements. Finally, we propose a general model for chromatin dynamics whereby most lineage-specific elements open in multipotent progenitors, and control both early pan-cardiopharyngeal and late cell-type-specific expression.
Project description:We have developed a protocol to generate cardiopharyngeal mesoderm (CPM) in vitro by Mesp1 induction in ES cells. The goal of this study is to compare the transcriptome of CPM-derived cardiac and skeletal myogenic progenitors to identify novel lineage-specific markers.
Project description:In vertebrates, pluripotent pharyngeal mesoderm progenitors produce the cardiac precursors of the second heart field as well as the branchiomeric head muscles and associated stem cells. However, the cellular and molecular mechanisms underlying the transition from multipotent progenitors to distinct heart and muscle precursors remain obscured by the complexity of vertebrate embryos. Here, using the ascidian Ciona intestinalis as a simple chordate model for cardiopharyngeal development, we show that bipotent progenitors are transcriptionally primed to activate both heart and pharyngeal muscle regulatory programs, which become restricted to the corresponding precursors following a conserved pattern of asymmetric divisions. Localized expression of COE (Collier/OLF1/EBF) then orchestrates the transition to a pharyngeal muscle fate both by promoting an MRF (Myogenic Regulatory Factor)-associated core myogenic program in myoblasts and by maintaining an undifferentiated state in their sister precursors through Notch-mediated lateral inhibition. Using single cell lineage tracing, we show that the latter are stem-like muscle precursors, which form most of the juvenile body wall muscles following proliferation, self-renewal, re-activation of MRF, and migration. We discuss the implications of our findings for the development and evolution of the cardiopharyngeal mesoderm in chordates. We combined fluorescence-activated cell sorting (FACS) and whole genome transcription profiling following perturbations of COE function to characterize the transcriptional dynamics underlying the specification of heart and ASM precursors in the ascidian cardiopharyngeal lineage. We used whole genome transcription profiling of FACS-purified cell populations isolated from 21 hpf larvae expressing FoxF>COE, FoxF>COE::WRPW or the FoxF>NLS::lacZ control. To gain insights into the transcriptional dynamics underlying fate specification in the cardiopharyngeal lineage, we also purified B7.5-lineage cells from control embryos and larvae collected every two hours from 8 to 28 hpf. This time window encompasses all developmental transitions from early TVC specification till ASM ring formation and initial differentiation.
Project description:Endothelial cells (EC) differentiate from multiple sources during embryonic development, including the cardiopharyngeal mesoderm, which gives rise to multiple tissues including the cardiac and branchiomeric muscle. Here, we have used a cardiogenic mesoderm cell differentiation model that also activates an endothelial transcription program. Comparing our chromatin remodeling data with publicly available single-cell RNA-seq data from mouse embryos, we derived a list of over 100 putative regulatory elements activated in EC marker genes. We applied a machine-learning strategy trained with validate enhancers to predict the probability of these sequences to function as enhancers. The computational assay returned over 50% of these sequences to be likely enhancers, some of which previously reported. In addition, using genetic and epigenetic perturbations of some of these elements, we established their requirement for gene expression during endothelial differentiation. Finally, we used the integration of multiple data sources and computational tools to search for transcriptional factor binding motifs related to endothelial cell fate specification. We found motifs of GATA, ETS, and FOS/AP-1 factors as the most significantly enriched in these sequences. Overall, our approach has been efficient in the identification of novel EC regulatory sequences with high likelihood to be enhancers, and validated a subset of them. Motif analyses revealed that the core EC transcription factors GATA/ETS/FOS is a likely driver of EC differentiation in cardiopharyngeal mesoderm.
Project description:Endothelial cells (EC) differentiate from multiple sources during embryonic development, including the cardiopharyngeal mesoderm, which gives rise to multiple tissues including the cardiac and branchiomeric muscle. Here, we have used a cardiogenic mesoderm cell differentiation model that also activates an endothelial transcription program. Comparing our chromatin remodeling data with publicly available single-cell RNA-seq data from mouse embryos, we derived a list of over 100 putative regulatory elements activated in EC marker genes. We applied a machine-learning strategy trained with validate enhancers to predict the probability of these sequences to function as enhancers. The computational assay returned over 50% of these sequences to be likely enhancers, some of which previously reported. In addition, using genetic and epigenetic perturbations of some of these elements, we established their requirement for gene expression during endothelial differentiation. Finally, we used the integration of multiple data sources and computational tools to search for transcriptional factor binding motifs related to endothelial cell fate specification. We found motifs of GATA, ETS, and FOS/AP-1 factors as the most significantly enriched in these sequences. Overall, our approach has been efficient in the identification of novel EC regulatory sequences with high likelihood to be enhancers, and validated a subset of them. Motif analyses revealed that the core EC transcription factors GATA/ETS/FOS is a likely driver of EC differentiation in cardiopharyngeal mesoderm.
Project description:Dynamic gene expression programs determine multipotent cell states and fate choices during development. Multipotent progenitors for cardiomyocytes and branchiomeric head muscles populate the pharyngeal mesoderm of vertebrate embryos, but the mechanisms underlying cardiopharyngeal multipotency and heart vs. head muscle fate choices remain elusive. The tunicate Ciona emerged as a simple chordate model to study cardiopharyngeal development with unprecedented spatio-temporal resolution. We analyzed the transcriptome of single cardiopharyngeal lineage cells isolated at successive time points encompassing the transitions from multipotent progenitors to distinct first and second heart, and pharyngeal muscle precursors. We reconstructed the three cardiopharyngeal developmental trajectories, and characterized gene expression dynamics and regulatory states underlying each fate choice. Experimental perturbations and bulk transcriptome analyses revealed that ongoing FGF/MAPK signaling maintains cardiopharyngeal multipotency and promotes the pharyngeal muscle fate, whereas signal termination permits the deployment of a full pan-cardiac program and heart fate specification. We identified the Dach1/2 homolog as a novel evolutionarily conserved second-heart-field-specific factor and demonstrate, through lineage tracing and CRISPR/Cas9 perturbations, that it operates downstream of Tbx1/10 to actively suppress the first heart lineage program. This data indicates that the regulatory state of multipotent cardiopharyngeal progenitors determines the first vs. second heart lineage choice, and that Tbx1/10 acts as a bona fide regulator of cardiopharyngeal multi potency. 1823 FACS purified Ciona cardiopharyngeal progenitor cells at successive developmental stages (12, 14, 16, 18, 20 hpfs) have been sequenced in this research, encompassing the developmental spectrum from single multipotent progenitors to diverse fate-restricted progenitor cells. 1796 out of 1823 cells have reads successfully mapped to Ciona genome (i.e only 1796 samples have FPKM data in the *txt processed data files). We adopted multiple quality control criteria to filter out low quality single cell transcriptomes, the contaminating subpopulations and the doublets. Eventually, 848 high-quality cells were retained for further analysis. Based on previously identified cell type specific markers and the well established lineage tree, we identified all five cardiopharyngeal progenitor subtypes (TVC, STVC, ASM, FHP, SHP) and in silico reconstructed three unidirectional trajectories corresponding to the specification of pharyngeal and cardiac fate. Our study enabled us to characterize the global gene expression patterns of heterogeneous cardiopharyngeal progenitors, and interrogate the spatial-temporal dynamics of cardiopharyngeal specification.