Project description:Xenopus embryonic ectodermal cells are responsive to various inducing factors. Mesoderm is specified and patterned by extracellular factors including FGF, Nodal, BMP and Wnt families. Pinhead is another secreted protein implicated in mesoderm formation. We found that Pinhead physically interacts with and antagonizes ADMP (anti-dorsalizing morphogenetic protein) that acts as BMP-like protein to promote ventral mesoderm formation. ADMP and BMPs have been shown to cooperate to activate phospho-Smad1 signaling to lead to ventral mesoderm development. Since Chordin is a BMP antagonist, we hypothesized that Pinhead together with Chordin can promote downregulation of phospho-Smad1 signaling that leads to dorsal mesoderm development. RNA sequencing revealed that Pinhead and Chordin synergize in dorsal mesoderm formation in ectodermal explants.
Project description:The pathways used by cells to transition between pluripotent and tissue-specific states are incompletely understood. Here we show that the widely-expressed transcription factor Oct1/Pou2f1 activates silent, developmental lineage-appropriate genes to “canalize” developmental progression. Using Oct1 inducible knockout embryonic stem cells, we show that that Oct1 deficiency impairs mesodermal and terminal muscle differentiation in a manner that can be rescued by Oct1 retroviral expression. We show that mesoderm-specific genes are not correctly induced early in the differentiation timecourse. Oct1-deficient cells lose temporal coherence in the induction of lineage-specific genes and show inappropriate developmental lineage branching, resulting in poorly differentiated cells states retaining epithelial characteristics. In embryonic stem cells, Oct1 co-binds with Oct4 to genes critical for mesoderm induction, and continues to bind these genes during differentiation. Oct1 binding events are enriched at the termini of chromatin loops, including loops gained with differentiation. The Utx/Kdm6a histone lysine demethylase also binds to many of these genes, and using a prototypic Pax3 gene we show that Oct1 recruits Utx to remove inhibitory H3K27me3 marks and activate expression. The specificity of the ubiquitous Oct1 protein for mesodermal genes can be explained by cooperative interactions with lineage-driving Smad transcription factors, as we show that Smad and Oct binding sites frequently coexist mesoderm-specific genes, and that Oct1 and Smad3 act cooperatively at the Myog enhancer. Overall, these results identify Oct1 as a key mediator of the induction of mesoderm lineage-specific genes.
Project description:The pathways used by cells to transition from undifferentiated, pluripotent gene expression programs into cell type-specific gene expression programs are incompletely understood. Here we show that the transcription factor Oct1/Pou2f1 recruits histone lysine demethylase complexes to allow for correct induction of silent, developmental lineage-specific genes and “canalize” developmental progression. Using mesodermal differentiation of inducible-conditional Oct1 knockout embryonic stem cells and single-cell gene expression profiling, we show that the potential to progress efficiently through mesodermal development is impaired in the Oct1 deficient condition. Oct1 deficient cells fail to form late presomitic mesoderm and early somite stage populations, and show “leaky” developmental trajectories with inappropriate lineage branching and accumulation of poorly differentiated cells that retain gene expression and metabolic hallmarks of pluripotency. Oct1 directly binds and regulates genes critical for developmental regulation, including genes encoding mesoderm-specific master regulators and components of chromatin regulatory complexes. Cells lacking Oct1 fail to positively resolve gene bivalency and activate gene expression by removing inhibitory H3K27me3 chromatin marks at mesoderm-specific genes. The Oct1 protein interacts with and recruits UTX to lineage-specific bivalent/poised targets, explaining the failure of Oct1 deficient cells to remove H3K27me3. Ectopic Oct1 expression improves the ability of cells to differentiate accurately under mesoderm lineage-inducing conditions.
Project description:The pathways used by cells to transition from undifferentiated, pluripotent gene expression programs into cell type-specific gene expression programs are incompletely understood. Here we show that the transcription factor Oct1/Pou2f1 recruits histone lysine demethylase complexes to allow for correct induction of silent, developmental lineage-specific genes and “canalize” developmental progression. Using mesodermal differentiation of inducible-conditional Oct1 knockout embryonic stem cells and single-cell gene expression profiling, we show that the potential to progress efficiently through mesodermal development is impaired in the Oct1 deficient condition. Oct1 deficient cells fail to form late presomitic mesoderm and early somite stage populations, and show “leaky” developmental trajectories with inappropriate lineage branching and accumulation of poorly differentiated cells that retain gene expression and metabolic hallmarks of pluripotency. Oct1 directly binds and regulates genes critical for developmental regulation, including genes encoding mesoderm-specific master regulators and components of chromatin regulatory complexes. Cells lacking Oct1 fail to positively resolve gene bivalency and activate gene expression by removing inhibitory H3K27me3 chromatin marks at mesoderm-specific genes. The Oct1 protein interacts with and recruits UTX to lineage-specific bivalent/poised targets, explaining the failure of Oct1 deficient cells to remove H3K27me3. Ectopic Oct1 expression improves the ability of cells to differentiate accurately under mesoderm lineage-inducing conditions.
Project description:Our understanding of how mesodermal tissue is formed, has been limited by the absence of specific and reliable markers of early mesoderm commitment. We report that mesoderm commitment from human embryonic stem cells (hESC) is initiated by Epithelial to Mesenchymal transition (EMT) as shown by gene expression profiling and by reciprocal changes in expression of the cell surface proteins, EpCAM/CD326 and NCAM/CD56. Molecular and functional assays reveal that CD326negCD56+ cells, generated from hESC in the presence of activin A, BMP4, VEGF and FGF2, represent a novel, multi-potent mesoderm-committed progenitor population. CD326negCD56+ progenitors are unique in their ability to generate all mesodermal lineages including hematopoietic, endothelial, mesenchymal (bone, cartilage, fat, fibroblast), smooth muscle and cardiomyocytes, while lacking the pluripotency of hESC. CD326negCD56+ cells are the precursors of previously reported, more lineage-restricted mesodermal progenitors. These findings present a novel approach to study how germ layer specification is regulated, and offer a unique target for tissue engineering. We used microarrays to compare gene expression profile of early mesodermal progenitors with undifferentiated hESC (H9 line). Mesoderm induction from hESC was initiatiated with combination of morphogens and growth factors including activin A, bone morphogenic protein 4, basic fibroblast growth factor and vascular endothelial growth factor. Proposed mesodermal progenitor population was isolated by FACS on day 3.5 of culture based on the presence of CD56 expression and the absenbce of CD326 expression.
Project description:In order to idetify paused promoters in vivo, we performed tissue specific Pol II Chip-seq using mutant embryos for the dorsal gradient. We used two population of cells, either dorsal ectoderm cells (gd7 embryos) or mesodermal cells (Toll10b) embryos. ChIP-seq for Pol II in various Drosophila embryos
Project description:5'Cap-Analysis of Gene Expression (5' CAGE) from mesodermal and whole embryo RNA at three different time intervals during development.
Project description:Whole-Genome Analysis of Dorsal-Ventral Patterning in the Drosophila Embryo. The maternal Dorsal regulatory gradient initiates the differentiation of several tissues in the early Drosophila embryo. Whole-genome microarray assays identified as many as 40 new Dorsal target genes, which encode a broad spectrum of cell signaling proteins and transcription factors. Evidence is presented that a tissue-specific form of the NF-Y transcription complex is essential for the activation of gene expression in the mesoderm. Tissue-specific enhancers were identified for new Dorsal target genes, and bioinformatics methods identified conserved cis-regulatory elements for coordinately regulated genes that respond to similar thresholds of the Dorsal gradient. The new Dorsal target genes and enhancers represent one of the most extensive gene networks known for any developmental process. Stathopoulos et al., Cell, Vol 111, 687-701, November 2002. Keywords: repeat sample
Project description:Rationale: Cardiogenesis is regulated by a complex interplay between transcription factors and chromatin-modifying enzymes. However, little is known about how these interactions regulate the transition from mesodermal precursors to cardiac progenitor cells (CPCs). Objective: To identify novel regulators of mesodermal cardiac lineage commitment. Methods and Results: We performed a bioinformatic-based transcription factor-binding site analysis on upstream promoter regions of genes that are enriched in ES cell-derived CPCs. From 32 candidate transcription factors screened, we found that YY1, a repressor of sarcomeric gene expression, is present in CPCs in vivo. Interestingly, we uncovered the ability of YY1 to transcriptionally activate Nkx2.5, a key marker of early cardiogenic commitment. YY1 regulates Nkx2.5 expression via a 2.1 kb cardiac-specific enhancer as demonstrated by in vitro luciferase-based assays and in vivo chromatin immunoprecipitation (ChIP) and genome-wide sequencing analysis. Furthermore, the ability of YY1 to activate Nkx2.5 expression depends on its cooperative interaction with GATA4 at a nearby chromatin. Cardiac mesoderm-specific loss-of-function of YY1 resulted in early embryonic lethality. This was corroborated in vitro by ES cell-based assays where we show that the over-expression of YY1 enhanced the cardiogenic differentiation ES cells into CPCs in a cell autonomous manner. Conclusion: These results demonstrate an essential and unexpected role for YY1 to promote cardiogenesis as a transcriptional activator of Nkx2.5 and other CPC-enriched genes. We report the identification of putative YY1 target genes in cardiac progenitor cells (CPCs). Two samples of independently FACS-purified eGFP+ CPCs were examined against the input.