Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Identification of direct T-box target genes in the developing zebrafish mesoderm

ABSTRACT: The zebrafish genes spadetail (spt) and no tail (ntl) encode T-box transcription factors that are important for early mesoderm development. Although much has been done to characterize these genes, the identity and location of target regulatory elements remain largely unknown. Here, we survey the genome for downstream target genes of the Spt and Ntl T-box transcription factors. We find evidence for extensive additive interactions towards gene activation and limited evidence for combinatorial and antagonistic interactions between the two factors. Using in vitro binding selection assays to define Spt- and Ntl-binding motifs, we searched for target regulatory sequence via a combination of binding motif searches and comparative genomics. We identified regulatory elements for tbx6 and deltaD, and, using chromatin immunoprecipitation, in vitro DNA binding assays and transgenic methods, we provide evidence that both are directly regulated by T-box transcription factors. We also find that deltaD is directly activated by T-box factors in the tail bud, where it has been implicated in starting the segmentation clock, suggesting that spt and ntl act upstream of this process. Keywords: Morpholino Knockdown We measured transcript levels in zebrafish embryos at 75% epiboly. We compared levels in spadetail (spt) and/or no tail (ntl) morpholino injected embryos to those in control embryos mock injected with Danieau solution plus 0.25% phenol red. Three biological replicates are included for each treatment.

ORGANISM(S): Danio rerio

SUBMITTER: Fiona Wardle

PROVIDER: E-GEOD-12857 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Identification of direct T-box target genes in the developing zebrafish mesoderm.

Garnett Aaron T AT Han Tina M TM Gilchrist Michael J MJ Smith James C JC Eisen Michael B MB Wardle Fiona C FC Amacher Sharon L SL

Development (Cambridge, England) 20090121 5

The zebrafish genes spadetail (spt) and no tail (ntl) encode T-box transcription factors that are important for early mesoderm development. Although much has been done to characterize these genes, the identity and location of target regulatory elements remain largely unknown. Here, we survey the genome for downstream target genes of the Spt and Ntl T-box transcription factors. We find evidence for extensive additive interactions towards gene activation and limited evidence for combinatorial and ...[more]

PMID: 19158186

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Project description:Microarrays have become established tools for describing microbial systems, however the assessment of expression profiles for environmental microbial communities still presents unique challenges. Notably, the concentration of particular transcripts are likely very dilute relative to the pool of total RNA, and PCR-based amplification strategies are vulnerable to amplification biases and the appropriate primer selection. Thus, we apply a signal amplification approach, rather than template amplification, to analyze the expression of selected lignin-degrading enzymes in soil. Controls in the form of known amplicons and cDNA from Phanerochaete chrysosporium were included and mixed with the soil cDNA both before and after the signal amplification in order to assess the dynamic range of the microarray. We demonstrate that restored prairie soil expresses a diverse range of lignin-degrading enzymes following incubation with lignin substrate, while farmed agricultural soil does not. The mixed additions of control cDNA with soil cDNA indicate that the mixed biomass in the soil does interfere with low abundance transcript changes, nevertheless our microarray approach consistently reports the most robust signals. Keywords: comparative analysis, microbial ecology, soil microbial communities We used lignin degradation as a model process to demonstrate the use of an oligonucleotide microarray for directly detecting gene expression in soil communities using signal amplification instead of template amplification to avoid the introduction of PCR bias. In the current study, we analyzed mRNA isolated from two distinct soil microbial communities and demonstrate our ability to detect the expression of a small subset of lignin degrading genes following exposure to a lignitic substrate. We also included purified control amplicons and mixed target experiments with pure P. chrysosporium genomic cDNA to determine the level of interference from soil biomass on target hybridization.

Project description:Using chromatin immunoprecipitation combined with microarrays we have identified targets of No tail (Ntl), a zebrafish Brachyury ortholog that plays a central role in mesoderm formation. We show that Ntl regulates a downstream network of other transcription factors and identify an in vivo Ntl binding site that resembles the consensus T-box binding site (TBS) previously identified by in vitro studies. We show floating head (flh) is a direct transcriptional target of Ntl in the notochord and that TBS in the flh upstream region are required for Ntl directed expression. Using this genome-scale data we have assembled a Gene Regulatory Network that describes mesoderm formation and patterning in the early zebrafish embryo and which predicts a role for Ntl in somite segmentation. Keywords: ChIP-chip Genomic array design. Microarrays were designed as described below and manufactured by Agilent Technologies (www.agilent.com). We have previously described the ChIP-chip technique in zebrafish and the design of promoter microarrays which cover a 2kb region around the transcription start sites (TSSs) of 11,512 zebrafish genes based on Zv4 (Wardle et al, 2006. Genome Biology 7:R71). In order to capture additional regulatory information further from the basal promoter region we also designed an expanded set of 60mer probes that cover 9kb upstream and 3kb downstream of the TSS of these genes using the same parameters as for the 2kb microarrays. We also incorporated several sets of control probes, both positive and negative. On each array there are 753 negative probes designed against zebrafish gene desert regions and Arabidopsis thaliana genes. In addition we included duplicates of promoter probes for several genes that we anticipated may be bound by factors of interest for this and other studies (wnt11, flh, vent, msgn1, myod, fgf8, pcdh8) and these probes are arrayed on both slides slide. We also included in this design 502 intensity control probes. Finally there are 2,256 controls added by Agilent. The final design contained 378,002 probes, including 365,537 experimental probes divided between nine microarray slides: slides 1-8 contained 40,616 experimental probes and slide 9 contained 40, 609. Further information on design and manufacture of the microarrays can be found on the Agilent Technologies website (www.agilent.com).

Dataset Information

Identification of direct T-box target genes in the developing zebrafish mesoderm

Publications

Identification of direct T-box target genes in the developing zebrafish mesoderm.

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