Rewiring of the epigenome and chromatin architecture by exogenously induced retinoic acid signaling during zebrafish embryonic development [ATAC-seq]
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ABSTRACT: Retinoic acid (RA) functions as a ligand for the nuclear RA receptors (RARs), which regulate the expression of target genes by binding to RA response elements. RA signaling is required for multiple processes during chordate embryonic development, such as body axis extension, hindbrain antero-posterior patterning and forelimb bud initiation. Although some RA target genes have been identified, little is known about the genome-wide effects of RA signaling during in vivo embryonic development. Here we stimulate the RA pathway during development by treating zebrafish embryos with all-trans-RA (atRA), the most abundant form of RA, and use a combination of RNA-seq, ATAC-seq, ChIP-seq and HiChIP to gain insight into the molecular mechanisms by which RA signaling control target gene expression. We find that RA signaling is involved in anterior/posterior patterning and development of the central nervous system, participating in the transition from pluripotency to differentiation. atRA treatment also induces alterations in chromatin accessibility during early development and promotes chromatin binding of RARaa and the RA targets Hoxb1b, Meis2b and Sox3, which cooperate in central nervous system development. Finally, we show that RA induces a rewiring of chromatin architecture, with alterations in chromatin 3D interactions that are consistent with target gene expression. This is illustrated by the specific induction of anterior HoxB genes by RARs, among other examples. Altogether, our findings identify genome-wide targets of RA signaling during embryonic development and provide a molecular mechanism by which developmental signaling pathways regulate the expression of target genes by altering chromatin topology.
Project description:Retinoic acid (RA) functions as a ligand for the nuclear RA receptors (RARs), which regulate the expression of target genes by binding to RA response elements. RA signaling is required for multiple processes during chordate embryonic development, such as body axis extension, hindbrain antero-posterior patterning and forelimb bud initiation. Although some RA target genes have been identified, little is known about the genome-wide effects of RA signaling during in vivo embryonic development. Here we stimulate the RA pathway during development by treating zebrafish embryos with all-trans-RA (atRA), the most abundant form of RA, and use a combination of RNA-seq, ATAC-seq, ChIP-seq and HiChIP to gain insight into the molecular mechanisms by which RA signaling control target gene expression. We find that RA signaling is involved in anterior/posterior patterning and development of the central nervous system, participating in the transition from pluripotency to differentiation. atRA treatment also induces alterations in chromatin accessibility during early development and promotes chromatin binding of RARaa and the RA targets Hoxb1b, Meis2b and Sox3, which cooperate in central nervous system development. Finally, we show that RA induces a rewiring of chromatin architecture, with alterations in chromatin 3D interactions that are consistent with target gene expression. This is illustrated by the specific induction of anterior HoxB genes by RARs, among other examples. Altogether, our findings identify genome-wide targets of RA signaling during embryonic development and provide a molecular mechanism by which developmental signaling pathways regulate the expression of target genes by altering chromatin topology.
Project description:Retinoic acid (RA) functions as a ligand for the nuclear RA receptors (RARs), which regulate the expression of target genes by binding to RA response elements. RA signaling is required for multiple processes during chordate embryonic development, such as body axis extension, hindbrain antero-posterior patterning and forelimb bud initiation. Although some RA target genes have been identified, little is known about the genome-wide effects of RA signaling during in vivo embryonic development. Here we stimulate the RA pathway during development by treating zebrafish embryos with all-trans-RA (atRA), the most abundant form of RA, and use a combination of RNA-seq, ATAC-seq, ChIP-seq and HiChIP to gain insight into the molecular mechanisms by which RA signaling control target gene expression. We find that RA signaling is involved in anterior/posterior patterning and development of the central nervous system, participating in the transition from pluripotency to differentiation. atRA treatment also induces alterations in chromatin accessibility during early development and promotes chromatin binding of RARaa and the RA targets Hoxb1b, Meis2b and Sox3, which cooperate in central nervous system development. Finally, we show that RA induces a rewiring of chromatin architecture, with alterations in chromatin 3D interactions that are consistent with target gene expression. This is illustrated by the specific induction of anterior HoxB genes by RARs, among other examples. Altogether, our findings identify genome-wide targets of RA signaling during embryonic development and provide a molecular mechanism by which developmental signaling pathways regulate the expression of target genes by altering chromatin topology.
Project description:Retinoic acid (RA) functions as a ligand for the nuclear RA receptors (RARs), which regulate the expression of target genes by binding to RA response elements. RA signaling is required for multiple processes during chordate embryonic development, such as body axis extension, hindbrain antero-posterior patterning and forelimb bud initiation. Although some RA target genes have been identified, little is known about the genome-wide effects of RA signaling during in vivo embryonic development. Here we stimulate the RA pathway during development by treating zebrafish embryos with all-trans-RA (atRA), the most abundant form of RA, and use a combination of RNA-seq, ATAC-seq, ChIP-seq and HiChIP to gain insight into the molecular mechanisms by which RA signaling control target gene expression. We find that RA signaling is involved in anterior/posterior patterning and development of the central nervous system, participating in the transition from pluripotency to differentiation. atRA treatment also induces alterations in chromatin accessibility during early development and promotes chromatin binding of RARaa and the RA targets Hoxb1b, Meis2b and Sox3, which cooperate in central nervous system development. Finally, we show that RA induces a rewiring of chromatin architecture, with alterations in chromatin 3D interactions that are consistent with target gene expression. This is illustrated by the specific induction of anterior HoxB genes by RARs, among other examples. Altogether, our findings identify genome-wide targets of RA signaling during embryonic development and provide a molecular mechanism by which developmental signaling pathways regulate the expression of target genes by altering chromatin topology.
Project description:Retinoic acid (RA) functions as a ligand for the nuclear RA receptors (RARs), which regulate the expression of target genes by binding to RA response elements. RA signaling is required for multiple processes during chordate embryonic development, such as body axis extension, hindbrain antero-posterior patterning and forelimb bud initiation. Although some RA target genes have been identified, little is known about the genome-wide effects of RA signaling during in vivo embryonic development. Here we stimulate the RA pathway during development by treating zebrafish embryos with all-trans-RA (atRA), the most abundant form of RA, and use a combination of RNA-seq, ATAC-seq, ChIP-seq and HiChIP to gain insight into the molecular mechanisms by which RA signaling control target gene expression. We find that RA signaling is involved in anterior/posterior patterning and development of the central nervous system, participating in the transition from pluripotency to differentiation. atRA treatment also induces alterations in chromatin accessibility during early development and promotes chromatin binding of RARaa and the RA targets Hoxb1b, Meis2b and Sox3, which cooperate in central nervous system development. Finally, we show that RA induces a rewiring of chromatin architecture, with alterations in chromatin 3D interactions that are consistent with target gene expression. This is illustrated by the specific induction of anterior HoxB genes by RARs, among other examples. Altogether, our findings identify genome-wide targets of RA signaling during embryonic development and provide a molecular mechanism by which developmental signaling pathways regulate the expression of target genes by altering chromatin topology.
Project description:Retinoid signaling is important for patterning the vertebrate hindbrain and midaxial regions. We recently showed that signaling through retinoic acid receptors (RARs) is essential for anteroposterior patterning along the entire body axis. To further investigate the mechanisms through which RARs act, we employed microarray analysis to investigate the effects of modulating RAR activity on target gene expression. We identified 334 upregulated genes (92% of which were validated) including known RA responsive genes, known genes that have never been proposed as RA targets and many hypothetical and unidentified genes (n = 166). 67 validated downregulated genes were identified including known RA responsive genes and anterior marker genes. The expression patterns of selected upregulated genes (n = 45) were examined at neurula stages using whole mount in situ hybridization. We found that most of these genes were expressed in the neural tube and many were expressed in anterior tissues such as neural crest, brain, eye anlagen, and cement gland. Some were expressed in tissues such as notochord, somites, pronephros and blood islands, where retinoic acid (RA) plays established roles in organogenesis. Members of this set of newly identified RAR target genes are likely to play important roles in neural patterning and organogenesis under the control of RAR signaling pathways and their further characterization will expand our understanding of RA signaling during development. Keywords = retinoid Keywords = microarray Keywords = RAR Keywords = neurula Keywords = anteroposterior patterning Keywords = and organogenesis
Project description:Retinoid signaling is important for patterning the vertebrate hindbrain and midaxial regions. We recently showed that signaling through retinoic acid receptors (RARs) is essential for anteroposterior patterning along the entire body axis. To further investigate the mechanisms through which RARs act, we employed microarray analysis to investigate the effects of modulating RAR activity on target gene expression. We identified 334 upregulated genes (92% of which were validated) including known RA responsive genes, known genes that have never been proposed as RA targets and many hypothetical and unidentified genes (n = 166). 67 validated downregulated genes were identified including known RA responsive genes and anterior marker genes. The expression patterns of selected upregulated genes (n = 45) were examined at neurula stages using whole mount in situ hybridization. We found that most of these genes were expressed in the neural tube and many were expressed in anterior tissues such as neural crest, brain, eye anlagen, and cement gland. Some were expressed in tissues such as notochord, somites, pronephros and blood islands, where retinoic acid (RA) plays established roles in organogenesis. Members of this set of newly identified RAR target genes are likely to play important roles in neural patterning and organogenesis under the control of RAR signaling pathways and their further characterization will expand our understanding of RA signaling during development. Keywords = retinoid Keywords = microarray Keywords = RAR Keywords = neurula Keywords = anteroposterior patterning Keywords = and organogenesis Keywords: repeat sample
Project description:Retinoic acid (RA), an active derivative of the liposoluble vitamin A (retinol), acts as an important signaling molecule during embryonic development, regulating phenomenons as diverse as anterior-posterior axial patterning, forebrain and optic vesicle development, specification of hindbrain rhombomeres, pharyngeal arches and second heart field, somitogenesis, and differentiation of spinal cord neurons. This small molecule directly triggers gene activation by binding to nuclear receptors (RARs), switching them from potential repressors to transcriptional activators. The repertoire of RA-regulated genes in embryonic tissues is poorly characterized. We performed a comparative analysis of the transcriptomes of murine wild-type and Retinaldehyde Dehydrogenase 2 null-mutant (Raldh2-/-) embryos - unable to synthesize RA from maternally-derived retinol - using Affymetrix DNA microarrays. Transcriptomic changes were analyzed in two embryonic regions: anterior tissues including forebrain and optic vesicle, and posterior (trunk) tissues, at early stages preceding the appearance of overt phenotypic abnormalities. Several genes expected to be downregulated under RA deficiency appeared in the transcriptome data (e.g. Emx2, Foxg1 anteriorly, Cdx1, Hoxa1, Rarb posteriorly), whereas reverse-transcriptase-PCR and in situ hybridization performed for additional selected genes validated the changes identified through microarray analysis. Altogether, the affected genes belonged to numerous molecular pathways and cellular/organismal functions, demonstrating the pleiotropic nature of RA-dependent events. In both tissue samples, genes upregulated were more numerous than those downregulated, probably due to feedback regulatory loops. Bioinformatic clustering analysis allowed us to extract groups of genes displaying similar behaviors in mutant tissue samples. These data give an overview of the gene expression changes occurring under a state of embryonic RA deficiency, and provide new candidate genes and pathways for a better understanding of retinoid-dependent molecular events. Two sets of samples were used for analyzing transcriptome changes in Raldh2-/- embryos. The rostral part of the head (including the anterior forebrain, optic vesicles, and overlying tissues), was collected from wild-type and mutant embryos at the 14 somite stage.The posterior tissues were analyzed at the 4 somite stage, and samples were collected from a transverse section plane excluding all tissues from the level of the first branchial arch.
Project description:Retinoic acid (RA), an active derivative of the liposoluble vitamin A (retinol), acts as an important signaling molecule during embryonic development, regulating phenomenons as diverse as anterior-posterior axial patterning, forebrain and optic vesicle development, specification of hindbrain rhombomeres, pharyngeal arches and second heart field, somitogenesis, and differentiation of spinal cord neurons. This small molecule directly triggers gene activation by binding to nuclear receptors (RARs), switching them from potential repressors to transcriptional activators. The repertoire of RA-regulated genes in embryonic tissues is poorly characterized. We performed a comparative analysis of the transcriptomes of murine wild-type and Retinaldehyde Dehydrogenase 2 null-mutant (Raldh2-/-) embryos - unable to synthesize RA from maternally-derived retinol - using Affymetrix DNA microarrays. Transcriptomic changes were analyzed in two embryonic regions: anterior tissues including forebrain and optic vesicle, and posterior (trunk) tissues, at early stages preceding the appearance of overt phenotypic abnormalities. Several genes expected to be downregulated under RA deficiency appeared in the transcriptome data (e.g. Emx2, Foxg1 anteriorly, Cdx1, Hoxa1, Rarb posteriorly), whereas reverse-transcriptase-PCR and in situ hybridization performed for additional selected genes validated the changes identified through microarray analysis. Altogether, the affected genes belonged to numerous molecular pathways and cellular/organismal functions, demonstrating the pleiotropic nature of RA-dependent events. In both tissue samples, genes upregulated were more numerous than those downregulated, probably due to feedback regulatory loops. Bioinformatic clustering analysis allowed us to extract groups of genes displaying similar behaviors in mutant tissue samples. These data give an overview of the gene expression changes occurring under a state of embryonic RA deficiency, and provide new candidate genes and pathways for a better understanding of retinoid-dependent molecular events.
Project description:The retinoic acid (RA) signaling pathway is essential for cardiac development; however, cardiomyocytes, the main cell type of the heart, are considered to be unresposive to RA signaling. The goal of this study was to examine the effects of all-trans RA (atRA) treatment on cardiomyocytes isolated from E18.5 mouse embryos. We found that cardiomyocytes, contrary to previous findings, are indeed repsonsive to RA signaling and that many genes involved in cardiac developmental and repair processes were significantly deregulated upon atRA trearment. These findings have important implications for the heart development and regeneration fields.
Project description:We report the continuous patterning and dynamic morphogenesis of hepatic, biliary and pancreatic structures, invaginating from a three-dimensional culture of human pluripotent stem cell (PSC). The boundary interactions between anterior and posterior gut spheroids differentiated from human PSCs enables autonomous emergence of hepato-biliary-pancreatic (HBP) organ domains specified at the foregut-midgut boundary organoids in the absence of extrinsic factor supply. The regional identity of the boundary region of anterior-posteior spheroids was analyzed by RNA-sequencing with micro-dissected boundary organoid into anterior, posterior, and boundary regions. Each region expressed the corresponding gut lineage markers. The early HBP specification markers including HHEX1 and PDX1 at the boundary were highly upregulated compared with the other two regions, indicating that the anterior-posterior boundary interactions autonomously generate HHEX and PDX1 positive cells in the absence of exogenous inductive factors. To delineate the HBP progenitor self-inductive mechanism, we evaluated the boundary specific expression profiles of known inductive signaling pathways that includes FGF, BMP, Hedgehog, NOTCH and retinoic acid (RA) signals, and found that the signal downstream of RA were activated prominently at the boundary region but not in the anterior or posterior regions.