Mechanisms of stretch-mediated skin expansion at single-cell resolution.

The ability of the skin to grow in response to stretching has been exploited in reconstructive surgery1. Although the response of epidermal cells to stretching has been studied in vitro2,3, it remains unclear how mechanical forces affect their behaviour in vivo. Here we develop a mouse model in which the consequences of stretching on skin epidermis can be studied at single-cell resolution. Using a multidisciplinary approach that combines clonal analysis with quantitative modelling and single-cell RNA sequencing, we show that stretching induces skin expansion by creating a transient bias in the renewal activity of epidermal stem cells, while a second subpopulation of basal progenitors remains committed to differentiation. Transcriptional and chromatin profiling identifies how cell states and gene-regulatory networks are modulated by stretching. Using pharmacological inhibitors and mouse mutants, we define the step-by-step mechanisms that control stretch-mediated tissue expansion at single-cell resolution in vivo.Wellcome Trust Royal Societ

Deciphering the Gene Regulatory Network Controlled by Mesp1 in Cardiovascular Progenitors During Mouse Heart Development

The heart is a vital organ of our body whose correct function is essential to life. During embryonic development, it arises from various pools of cardiovascular progenitors (CPs) that are specified in a precise spatiotemporal pattern during gastrulation. Correct specification of the various populations of CPs is dependent upon coordinated action of transcription factors (TFs) that together control gene expression in space and time, thereby defining the cellular identity of CPs. These molecular events are to date poorly described in nascent CPs. Mesp1 is a master TF that promotes CP specification and differentiation. Using mouse pluripotent stem cells (PSCs) as a model for gene regulation during early development, we performed RNA-seq, Mesp1, H3K27Ac and H3K4me1 ChIP-seq as well as ATAC-seq during differentiation of PSCs in which the expression of Mesp1 can be induced in a doxycycline-dependent manner. We uncovered the various patterns of gene regulation that are arise within 24 hours of Mesp1 induction, including rapid activation of some genes and delayed activation of others. Using Mesp1 ChIP-seq, we characterized the direct and indirect Mesp1 target genes in a genome-wide manner. We then defined and validated the activity of distal regulatory elements that enable the activation of Mesp1 target genes. Motif enrichment analysis at Mesp1 binding sites uncovered several potential cofactors of Mesp1. Using a variety of in vitro and in vivo validation methods, we identified Zic2 and Zic3 as essential cofactors of Mesp1, which together regulate its ability to open the chromatin as well as regulate its target gene expression during CP specification. Then, we explored the mechanisms of Mesp1-mediated enhancer activation in CPs through enhancer reporter assays, demonstrating the potential and specificity of Mesp1-bound enhancers to activate gene expression in a cell-type specific manner, opening the way to dissecting the motif grammar of CP-specific enhancers in future experiments. Finally, using single-cell RNA-seq and ATAC-seq during PSC differentiation after Mesp1 induction, we shed light on how the induction of one single master transcription factor can induce specification and differentiation of various cardiovascular lineages. Altogether, our work provides novel insights into the structure and function of the gene regulatory network governing early CP specification, thereby improving our understanding of early cardiovascular development.Le cœur est un organe dont le bon fonctionnement est essentiel à la vie. Pendant le développement embryonnaire, il se forme à partir de différentes populations de progéniteurs cardiovasculaires (PCs) qui se spécifient selon un schéma spatiotemporel précis durant la gastrulation. L’agencement et la genèse de ces derniers dépend de l’action coordonnée de facteurs de transcription (FT) qui régulent l’expression des gènes dans le temps et dans l’espace, définissant ainsi l’identité de ces progéniteurs. Ces évènements moléculaires restent peu décrits dans les PCs précoces. Mesp1 est un FT qui promeut la spécification et la différentiation des PCs. En utilisant les cellules souches pluripotentes (CSP) dans lesquelles l’expression de Mesp1 peut être induite par la doxycycline comme modèle pour la régulation des gènes pendant l’embryogenèse précoce, nous avons réalisé du RNA-seq, Mesp1, H3K27Ac et H3K4me1 ChIP-seq ainsi que de l’ATAC-seq pendant la différentiation de ces CSP avec et sans induction de Mesp1. Nous avons découvert que Mesp1 active différents gènes avec des cinétiques d’expression distinctes, certains gènes répondant plus rapidement à l’induction de Mesp1 que d’autres. En analysant le Mesp1 ChIP-seq, nous avons caractérisé les gènes qui sont directement versus indirectement régulés par Mesp1 dans le génome entier. Ensuite, nous avons défini et validé la fonction de régions régulatrices liées par Mesp1 pour l’activation de certains de ces gènes cibles. L’analyse de ces sites par enrichissement de motif prédit les cofacteurs potentiels de Mesp1. En utilisant une large gamme de méthodes in vivo et in vitro, nous avons validé que Zic2 et Zic3 agissent comme des cofacteurs essentiels à Mesp1, en régulant sa capacité à ouvrir la chromatine et l’expression de ces gènes cibles. Ensuite, nous avons exploré les mécanismes d’activation des régions régulatrices liées par Mesp1 via des constructions reportrices, démontrant ainsi le potentiel et la spécificité de ces séquences à activer l’expression des gènes spécifiquement dans les progéniteurs cardiaques. Finalement, nous avons réalisé du single-cell RNA-seq et ATAC-seq après l’induction de Mesp1 pendant la différentiation des PSC, ce qui nous a permis de mettre en lumière l’apparition de différents types cellulaires cardiovasculaires par l’induction d’un seul « maître » FT. En conclusion, mon travail expose de nouvelles facettes de la structure et la fonction du réseau de régulation génétique qui contrôle la spécification des PC et enrichit notre savoir sur le développement cardiovasculaire précoce.Doctorat en Sciences biomédicales et pharmaceutiques (Médecine)info:eu-repo/semantics/nonPublishe

Cardiopharyngeal Progenitor Specification: Multiple Roads to the Heart and Head Muscles

info:eu-repo/semantics/publishe

Cardiopharyngeal progenitor specification: multiple roads to the heart and head muscles

International audienceDuring embryonic development, the heartarise from various sourcesof undifferentiated mesodermal progenitors, with an additional contribution from ectodermal neural crest cells. Mesodermal cardiac progenitorsareplasticand multipotent,but are nevertheless specified to a precise heart region and cell type very early during development. Recent findings have defined both this lineage plasticity and early commitment of cardiac progenitors, using a combination of single-cell and population analyses. In this review, we discuss several aspects of cardiac progenitor specification. We discuss their markers, fate potential in vitroand in vivo, early segregation and commitment, and also intrinsic and extrinsic cues regulatinglineage restrictionfrom multipotency to a specific cell type of the heart. Finally, we also discuss the sub-divisionsof the cardiopharyngeal field, and the shared origins of the heart with other mesodermal derivatives, including head and neck muscles

Cardiopharyngeal progenitor specification: multiple roads to the heart and head muscles

International audienceDuring embryonic development, the heartarise from various sourcesof undifferentiated mesodermal progenitors, with an additional contribution from ectodermal neural crest cells. Mesodermal cardiac progenitorsareplasticand multipotent,but are nevertheless specified to a precise heart region and cell type very early during development. Recent findings have defined both this lineage plasticity and early commitment of cardiac progenitors, using a combination of single-cell and population analyses. In this review, we discuss several aspects of cardiac progenitor specification. We discuss their markers, fate potential in vitroand in vivo, early segregation and commitment, and also intrinsic and extrinsic cues regulatinglineage restrictionfrom multipotency to a specific cell type of the heart. Finally, we also discuss the sub-divisionsof the cardiopharyngeal field, and the shared origins of the heart with other mesodermal derivatives, including head and neck muscles

Epidermal autonomous VEGFA/Flt1/Nrp1 functions mediate psoriasis-like disease.

Psoriasis is a common chronic skin disorder characterized by keratinocyte hyperproliferation with altered differentiation accompanied by inflammation and increased angiogenesis. It remains unclear whether the first events that initiate psoriasis development occur in keratinocytes or inflammatory cells. Here, using different psoriasis mouse models, we showed that conditional deletion of Flt1 or Nrp1 in epidermal cells inhibited psoriasis mediated by Vegfa overexpression or c-Jun/JunB deletion. Administration of anti-Nrp1 antibody reverted the psoriasis phenotype. Using transcriptional and chromatin profiling of epidermal cells following Vegfa overexpression together with Flt1 or Nrp1 deletion, we identified the gene regulatory network regulated by Vegfa/Nrp1/Flt1 during psoriasis development and uncovered a key role of Fosl1 in regulating the chromatin remodeling mediated by Vegfa overexpression in keratinocytes. In conclusion, our study identifies an epidermal autonomous function of Vegfa/Nrp1/Flt1 that mediates psoriatic-like disease and demonstrates the clinical relevance of blocking Vegfa/Nrp1/Flt1 axis in psoriasis.info:eu-repo/semantics/publishe

Defining the earliest step of cardiovascular lineage segregation by single-cell RNA-seq.

Mouse heart development arises from Mesp1-expressing cardiovascular progenitors (CPs) that are specified during gastrulation. The molecular processes that control early regional and lineage segregation of CPs have been unclear. We performed single-cell RNA sequencing of wild-type and Mesp1-null CPs in mice. We showed that populations of Mesp1 CPs are molecularly distinct and span the continuum between epiblast and later mesodermal cells, including hematopoietic progenitors. Single-cell transcriptome analysis of Mesp1-deficient CPs showed that Mesp1 is required for the exit from the pluripotent state and the induction of the cardiovascular gene expression program. We identified distinct populations of Mesp1 CPs that correspond to progenitors committed to different cell lineages and regions of the heart, identifying the molecular features associated with early lineage restriction and regional segregation of the heart at the early stage of mouse gastrulation

Defining the earliest step of cardiovascular lineage segregation by single cell RNA-seq

Mouse heart development arises from Mesp1-expressing cardiovascular progenitors (CPs) that are specified during gastrulation. The molecular processes that control early regional and lineage segregation of CPs have been unclear. We performed single-cell RNA sequencing of wild-type and Mesp1-null CPs in mice. We showed that populations of Mesp1 CPs are molecularly distinct and span the continuum between epiblast and later mesodermal cells, including hematopoietic progenitors. Single-cell transcriptome analysis of Mesp1-deficient CPs showed that Mesp1 is required for the exit from the pluripotent state and the induction of the cardiovascular gene expression program. We identified distinct populations of Mesp1 CPs that correspond to progenitors committed to different cell lineages and regions of the heart, identifying the molecular features associated with early lineage restriction and regional segregation of the heart at the early stage of mouse gastrulation.SCOPUS: ar.jinfo:eu-repo/semantics/publishe