Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Studies on Xenopus laevis intestine reveal biological pathways underlying vertebrate gut adaptation from embryo to adult

ABSTRACT: To adapt to its changing dietary environment, the digestive tract is extensively remodeled from the embryo to the adult during vertebrate development. Xenopus laevis metamorphosis is an excellent model system for studying mammalian gastrointestinal development and is used to determine the genes and signaling programs essential for intestinal development and maturation. The metamorphosing intestine can be divided into four distinct developmental time points and these were analyzed with X. laevis microarrays. Due to the high level of conservation in developmental signaling programs and homology to mammalian genes, annotations and bioinformatics analysis were based on human orthologs. Clustering of the expression patterns revealed co-expressed genes involved in essential cell processes such as apoptosis and proliferation. The two largest clusters of genes have expression peaks and troughs at the climax of metamorphosis respectively. Novel conserved gene ontology categories regulated during this period include transcriptional activity, signal transduction, and metabolic processes. Interestingly, the induced genes associated with metamorphic climax correlated with the gene expression peaks observed around birth in the mouse intestine. Thus both mouse and amphibian, share similarities at the molecular levels for intestinal maturation and remodeling, which appears to be under the influence of increasing levels of circulating thyroid hormone. Moreover, our genome-wide analysis of the intestine during development identified larval/embryo- and adult-specific genes. Detailed analysis revealed 17 larval specific genes that may represent molecular markers for human colonic cancers, while many adult specific genes are associated with dietary enzymes. This global developmental expression study provides the first detailed molecular description of intestinal remodeling and maturation during postembryonic development, which should help improve our understanding of intestinal organogenesis and human diseases. This study significantly contributes towards our understanding of the dynamics of molecular regulation during development and tissue renewal, which is important for future basic and clinical research and for medicinal applications. Time series experiment through natural metamorphosis of intestine in Xenopus laevis. Biological replicates: 3 replicates for each stage of major change during amphibian metamorphosis (except in the climax where 2 bioogical replicates were used). Universal reference design was used instead of dye-swap design for 2-color hybridizations.

ORGANISM(S): Xenopus laevis

SUBMITTER: Biswajit Das

PROVIDER: E-GEOD-21303 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Hydroxylated polychlorinated biphenyls are the metabolites produced from polychlorinated biphenyls (PCBs) by drug-metabolizing enzyme cytochrome P450 1A1. These compounds are bound to transthyretin, a major plasma thyroid hormone-binding protein in amphibian tadpoles. The compounds-transthyretin complexes are transferred into the brain across the blood brain barrier in mammals. Thus these compounds are suspected to disrupt neural development in brain. We studied about the effects of hydroxylated PCBs on the thyroid system in brain using metamorphosing tadpoles of African clawed toad, Xenopus laevis. The metamorphosis assay revealed that these compounds had inhibitory effects on the thyroid hormone-induced metamorphosis. This in vivo assay was a powerful tool to detect thyroid-disrupting activities, because we were not able to detect the inhibitory effects of these compounds using thyroid hormone-responsive reporter gene assay in a cultured Xenopus cell line. A genome-wide gene expression analysis in brain following short-term exposure to these compounds demonstrated that the delay of metamorphosis and the morphological thyroid-disrupting changes could be caused partially by disruption of the thyroid hormone-induced gene expression by hydroxylated PCBs. Furthermore, we associated functional ontology terms with the transcripts whose expression were altered by thyroid hormone alone, or thyroid hormone and hydroxylated PCBs. We suggested that these approachs using a technique of bioinformatics revealed molecular mechanism of thyroid-disrupting activities in vivo. Thyroid hormones induce amphibian metamorphosis and alter a lot of thyroid hormone-responsive gene expression. We studied about the effects of hydroxylated PCBs on TH-induced gene expression. Premetamorphic tadpoles were treated with 500 nM hydroxylated PCBs in the presence of 1 nM thyroid hormone for 4 days. After exposure period total RNA was extracted from brain. Study included at least three replicate of each treatment.

Project description:Post-translational modifications (PTMs) of histones exert fundamental roles in regulating gene expression. During development, groups of PTMs are constrained by unknown mechanisms into combinatorial patterns, which facilitate transitions from uncommitted embryonic cells into differentiated somatic cell lineages. Repressive histone modifications such as H3K9me3 or H3K27me3 have been investigated in detail, but the role of H4K20me3 in development is currently unknown. Here we show that Xenopus laevis Suv4-20h1 and h2 histone methyltransferases (HMTases) are essential for induction and differentiation of the neuroectoderm. Morpholino-mediated knockdown of the two HMTases leads to a selective and specific downregulation of genes controlling neural induction, thereby effectively blocking differentiation of the neuroectoderm. Global transcriptome analysis supports the notion that these effects arise from the transcriptional deregulation of specific genes rather than widespread, pleiotropic effects. Interestingly, morphant embryos fail to repress the Oct4-related Xenopus gene Oct-25. We validate Oct-25 as direct target of xSu4-20h enzyme-mediated gene repression, showing by chromatin immunoprecipitaton that it is decorated with the H4K20me3 mark downstream of the promoter in normal, but not in double-morphant, embryos. Since knockdown of Oct-25 protein significantly rescues the neural differentiation defect in xSuv4-20h double-morphant embryos, we conclude that the epistatic relationship between Suv4- 20h enzymes and Oct-25 controls the transit from pluripotent to differentiation-competent neural cells. Consistent with these results in Xenopus, murine Suv4-20h1/h2 double-knockout embryonic stem (DKO ES) cells exhibit increased Oct4 protein levels before and during EB formation, and reveal a compromised and biased capacity for in vitro differentiation, when compared to normal ES cells. Together, these results suggest a regulatory mechanism, conserved between amphibian and mammals, in which H4K20me3-dependent restriction of specific POU-V genes directs cell fate decisions, when embryonic cells exit the pluripotent state. Total RNA samples from Xenopus laevis embryos. Transcript levels were analyzed after injection of control or Suv420 morpholinos into blastomeres.

Project description:Purpose: To identify orthologous genes in Xenopus that are implicated in deafness and vestibular disorders in humans and to compare RNA-Seq and microarray to determine the advantages of each technology for Xenopus transcriptomic analysis. Methods: Inner ear RNA from X. laevis stages 56-58 was isolated with the QiagenÂ® RNeasyÂ® Mini Kit. RNA quality was assessed using the Agilent 2100 Bioanalyzer. The RNA was sent to the National Center for Genome Resources, for Illumina-Solexa sequencing using the genome analyzer II and to MIT for microarray processing usign the Affymetrix GeneChipÂ® X. laevis Genome 2.0 Array. The OMIM database was mined for identification of genes causing deafness and vestibular disorder in humans. Human sequences for each of the deafness and vestibular disorders genes were downloaded from Ensembl. Blast-2.2.27+ was used to mapped the human sequences against X. tropicalis predicted proteins from JGI or to Xenopus consensus sequences downloaded from Affymetrix. The alignment of the human sequences to the predicted proteins resulted in the identification of the protein designation number. The protein designation number was used to obtain the sacaffold number and coordinates from JGI genome browser. The scaffold number and coordinates were input into Alpheus sequence variant detection pipeline to obtain the number of reads associated with each gene. The reads were log2 transformed for comparison to the microarray. In the case of the alignment of the human sequences to the Xenopus consensus sequences resulted in the PSID. The PSID was used to obtain the GCRMA intensity value. The GCRMA value and the number of reads were compared to determine which technology detected more genes. Results: Using Affymetrix GeneChipÂ® X. laevis Genome 2.0 Arrays and Illumina-Solexa sequencing methods, we determined that the transcriptional profile of the Xenopus inner ear comprises hundreds of genes that are orthologous to OMIMÂ® genes implicated in deafness and vestibular disorders in humans. Analysis of genes that mapped to both technologies showed that RNA-Seq detected more of both deafness and vestibular disorder than the Microarray. RNA-Seq and microarray detected 108 genes but RNA-Seq detected 48 genes that were below threshold criteria for microarray. While the microarray detected 11 genes that were below the expression criteria for RNA-Seq and 23 genes were below the threshold criteria for both technologies. Further analysis of the 108 genes detected by both technologies showed a minor correlation between the two technologies. Conclusions: As part of this study we identified candidate scaffold regions of the Xenopus tropicalis genome that can be used for gene mutagenesis. Furthermore, results from this study showed that the two technologies can complement each other and that a combination of both approaches can provide a more complete analysis of gene expression than either method alone. Inner ear RNA from X. laevis larval stages 56-58 was isolated and shipped to the National Center for Genome Resources, for Illumina-Solexa sequencing or to the Massachusetts Institute of Technology BioMicro Center for microarray analysis with the Affymetrix GeneChipÂ® X. laevis Genome 2.0 Array. RNA-Sequencing was completed using the Illumina-Solexa platform for sequencing by synthesis. Short-insert paired end (SIPE) libraries were prepared from total RNA according to Illuminaâ??s mRNA-Seq Sample Prep Protocol v2.0 (Illumina, San Diego, CA, USA). The resultant double-stranded cDNA concentration was measured on a NanoDrop spectrophotometer, and size and purity were determined on the 2100 Bioanalyzer using a DNA 1000 Nano kit. The cDNA libraries were cluster amplified on Illumina flowcells, sequenced on the GAII Sequencer as 36-cycle single-end reads, and processed using Illumina software v1.0. Illumina reads were aligned to the X. tropicalis genome using the algorithm for genomic mapping and alignment program (GMAP) and AlpheusÂ® Sequence Variant Detection System v3.1.

Project description:Exostosin 1 (Ext1) is a glycosyltransferase involved in the biosynthesis of the extracellular matrix Heparan Sulfate Proteoglycan (HSPG). Knockdown of Ext1 caused gastrulation defects and formation of an abnormal body axis. Since ext1 has been implicated as an indirect contributor to multiple signaling pathways in vertebrate development, microarray was used to identify genes expressed in gastrulae that would be affected by a reduction in ext1 expression. Microarray-based comparisons of gene expression in control vs. Ext1 MO embryos showed that Ext1 is involved in regulating genes that are related to metabolic process, development and signaling pathways. Half of the hits from the microarray are uncharacterized genes. Approximately forty-five percent of genes are related to metabolic process and thirty percent of genes are belonged to signaling and developmental process categories. Ten percent of each up-regulated and down-regulated gene set is predicted to function in establishment of localization by GO, which is consistent with EXT1 being involved in the movement of extracellular substances. The transcription factors or signaling protein, Isl1, Pitx2, TBX5A, Wnt5A, Wnt7A, WT1, Pax3, Wnt1, and Xbra were identified as Ext1 regulated genes. This analysis investigating the role of Ext1 during gastrulation and provide the information that EXT1 plays an important role in Xenopus early development. Exostosin 1 (EXT1) is a glycosyltransferase involved in the biosynthesis of the extracellular matrix Heparan Sulfate Proteoglycan (HSPG). Knockdown of EXT1 caused gastrulation defects and formation of an abnormal body axis. Since ext1 has been implicated as an indirect contributor to multiple signaling pathways in vertebrate development, microarray was used to identify genes expressed in gastrulae that would be affected by a reduction in ext1 expression. Microarray-based comparisons of gene expression in control vs. EXT1 MO embryos showed that EXT1 is involved in regulating genes that are related to metabolic process, development and signaling pathways. Half of the hits from the microarray are uncharacterized genes. Approximately forty-five percent of genes are related to metabolic process and thirty percent of genes are belonged to signaling and developmental process categories. Ten percent of each up-regulated and down-regulated gene set is predicted to function in establishment of localization by GO, which is consistent with EXT1 being involved in the movement of extracellular substances. The transcription factors or signaling protein, Isl1, Pitx2, TBX5A, Wnt5A, Wnt7A, WT1, Pax3, Wnt1, and Xbra were identified as EXT1 regulated genes. This analysis investigating the role of EXT1 during gastrulation and provide the information that EXT1 plays an important role in Xenopus early development. The embryos were injected with mispair or Ext1 MO were collected at St. 10.5. The RNA was extracted and for probe synthesis and the hybridization was performed on Affymetrix Xenopus laevis genome v2.0 array. The experiments were repeated for three times. Results of paired control and experimental samples were compared.

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Studies on Xenopus laevis intestine reveal biological pathways underlying vertebrate gut adaptation from embryo to adult

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