Unknown,Transcriptomics,Genomics,Proteomics

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Resolution of ntla-dependent transcriptome at 16 hpf using caged molecules

ABSTRACT: Transcription factors play diverse roles during embryonic development, combinatorially controlling multiple cellular states in a spatially and temporally defined manner. Resolving the dynamic transcriptional profiles that underlie these patterning processes is essential for understanding embryogenesis at the molecular level. Here we show how temporal, tissue-specific changes in embryonic transcription factor function can be discerned by integrating caged morpholinos (cMOs) with photoactivatable fluorophores, fluorescence-activated cell sorting (FACS), and microarray technologies. As a proof of principle, we have dynamically profiled No tail-a (Ntla)-dependent genes at different stages of axial mesoderm development in zebrafish, discovering and characterizing discrete sets of transcripts that are coincident with either notochord cell fate commitment or differentiation. Our studies demonstrate how optically controlled chemical tools can be use to probe developmental processes with spatiotemporal precision and reveal the sequential activation of distinct transcriptomes within a cell lineage by a single transcriptional factor. Zebrafish zygotes were injected with a mixture of ntla caged morpholino (cMO) and caged fluorescein dextran (cFD), and a 100 µm-diameter region of the posterior chordamesoderm 125 μm anterior to the center of Kupffer’s vesicle was UV-irradiated at 12 hours post fertilization (hpf). The UV irradiation generated an active morpholino targeting the ntla 5'UTR and simultaneously labeled the cells with green fluorescence. By 36 hpf, the irradiated, green-fluorescent cells contributed to both notochord and floor plate, but the notochord cells were partially vacuolated and disorganized. Combining these caged reagents with microarray analysis identified transcriptional changes coincident with loss of ntla at 16 hpf and subsequent notochord differentiation. Zebrafish zygotes were injected with a mixture of ntla cMO/cFD, and a 100 µm-diameter region of the posterior chordamesoderm 125 μm anterior to the center of Kupffer’s vesicle was UV-irradiated at 12 hpf. Control embryos were injected with cFD and similarly irradiated at 12 hpf. Experimental and control sets of embryos were enzymatically dissociated at 16 hpf, green-fluorescent cells were isolated by FACS, and collected in trizol. Thirty embryos were used for each experiment or controls, each yielding approximately 8,000 green fluorescent cells. Five biological replicates were performed along with five paired controls. Total RNA was isolated from each sample, reverse transcribed, and amplified using WTA2 TransPlex Complete Whole Transcriptome Amplification kit (Sigma) using a miniaturized procedure and manufacturer-recommended incubation steps. The synthesized cDNA was sent to Nimblegen for dye labeling and hybridization. Samples were hybridized to the Nimblegen 2007 (Zv 7) Danio rerio Gene Expression Array chip using one dye per chip. Raw probe data (.pair file) was subjected to RMA, normalization, background correction, and generation of gene expression summary (.calls file) by Nimblegen. Processed data was analyzed in ArrayStar software (DNAStar). Significantly affected genes (fold change > 2 and p-value < 0.10) were identified using a moderated t-test.

ORGANISM(S): Danio rerio

SUBMITTER: James Chen

PROVIDER: E-GEOD-31881 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Transcription factors play diverse roles during embryonic development, combinatorially controlling multiple cellular states in a spatially and temporally defined manner. Resolving the dynamic transcriptional profiles that underlie these patterning processes is essential for understanding embryogenesis at the molecular level. Here we show how temporal, tissue-specific changes in embryonic transcription factor function can be discerned by integrating caged morpholinos (cMOs) with photoactivatable fluorophores, fluorescence-activated cell sorting (FACS), and microarray technologies. As a proof of principle, we have dynamically profiled No tail-a (Ntla)-dependent genes at different stages of axial mesoderm development in zebrafish, discovering and characterizing discrete sets of transcripts that are coincident with either notochord cell fate commitment or differentiation. Our studies demonstrate how optically controlled chemical tools can be use to probe developmental processes with spatiotemporal precision and reveal the sequential activation of distinct transcriptomes within a cell lineage by a single transcriptional factor. Zebrafish zygotes were injected with a mixture of ntla caged morpholino (cMO) and caged fluorescein dextran (cFD), and a 100 µm-diameter region of the shield was UV-irradiated at 6 hours post fertilization (hpf). The UV irradiation generated an active morpholino targeting the ntla 5'UTR and simultaneously labeled the cells with green fluorescence. By 36 hpf, the irradiated, green-fluorescent cells contributed to the medial floor plate rather than the notochord, consistent with earlier proposals that Ntla acts as a transcriptional switch between these two cell fates. Combining these caged reagents with microarray analysis identified transcriptional changes coincident with loss of ntla at 9 hpf and subsequent notochord fate respecification. Zebrafish zygotes were injected with a mixture of ntla cMO/cFD, and a 100 µm-diameter region of the shield was UV-irradiated at 6 hpf. Control embryos were injected with cFD and similarly irradiated at 6 hpf. Experimental and control sets of embryos were enzymatically dissociated at 9 hpf, green-fluorescent cells were isolated by FACS, and collected in trizol. Thirty embryos were used for each experiment or controls, each yielding approximately 8,000 green fluorescent cells. Five biological replicates were performed along with five paired controls. Total RNA was isolated from each sample, reverse transcribed, and amplified using WTA2 TransPlex Complete Whole Transcriptome Amplification kit (Sigma) using a miniaturized procedure and manufacturer-recommended incubation steps. The synthesized cDNA was sent to Nimblegen for dye labeling and hybridization. Samples were hybridized to the Nimblegen 2007 (Zv 7) Danio rerio Gene Expression Array chip using one dye per chip. Raw probe data (.pair file) was subjected to RMA, normalization, background correction, and generation of gene expression summary (.calls file) by Nimblegen. Processed data was analyzed in ArrayStar software (DNAStar). Significantly affected genes (fold change > 2 and p-value < 0.10) were identified using a moderated t-test.

Project description:Within the regulatory framework on the approval of new substances, the assessment of immunotoxic modes of action (MoA) is currently not covered. This is not least due to the lack of standardized methods and reliable validated biomarkers for immunotoxic effects. The experimental set up was designed to analyze the compound-specific response of zebrafish embryos to two immunomodulative reference substances, clobetasol propionate (CP, CAS 25122-46-7) and imiquimod (IMQ, CAS 99011-02-6), on the global level of gene expression. The obtained results were used to (i) identify potential biomarker candidates for the assessment of immunotoxic MoAs, (ii) identify compound-specific molecular signatures, (iii) evaluate the reliability of data acquisition using OMICs-coupled approaches and (iv) to assess the suitability of the zebrafish embryo as an alternative model for the human-representative investigation of psoriatic effects. For this, the transcriptomic profiles of embryos were bioinformatically analysed subsequent to an CP-induced immunosuppression in absence or presence of an IMQ-induced immune challenge, i.e. the simulation of a resting and an activated immune system. In a modified version of the zebrafish embryo toxicity test (OECD 236), 15 fertilized eggs were exposed to either CP (250 nM) or to IMQ (4000 nM) or to a combination of both under semi static conditions. Exposure to CP started at 2 hours post fertilization (hpf) until 72 hpf. Exposure to IMQ started at 48 hpf until 72 hpf. Untreated embryos reared in medium without CP nor IMQ dissolved was used as a negative control. All conditions comprised three biological replicates. Medium was exchanged on a daily basis by renewing half its volume. Occurrence of morphological changes and indicators of lethality as described in the OECD test guideline 236 were examined microscopically on a daily basis. At 72 hpf, all larvae were pooled for each sample for RNA extraction using a NucleoSpin RNA/Protein kit (Macherey-Nagel) following the manufacturer’s protocol. RNA quality was assessed with a 2100 Bioanalyzer system (Agilent) before coding RNA was purified (PolyA selection with TruSeq RNA Library Prep Kit v2) and sequenced on an Illumina NovaSeq 6000 System (Illumina) in 150 bp paired-end mode, producing a minimum of 30 million reads per sample. Adapter sequences were removed with trimmomatic and sequences were aligned to the Danio rerio reference genome GRCz11 with STAR. Counting of feature mapped reads was performed through featureCounts. Library gene count tables were then merged to a single count matrix as input for differential gene expression analysis with DESeq2.

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Resolution of ntla-dependent transcriptome at 16 hpf using caged molecules

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