Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Genome-wide RNA tomography in the zebrafish embryo

ABSTRACT: Advancing our understanding of embryonic development is heavily dependent on identification of novel pathways or regulators. While genome-wide techniques such as RNA sequencing are ideally suited for discovering novel candidate genes, they are unable to yield spatially resolved information in embryos or tissues. Microscopy-based approaches, using for example in situ hybridization, can provide spatial information about gene expression, but are limited to analyzing one or a few genes at a time. Here, we present a method where we combine traditional histological techniques with low-input RNA sequencing and mathematical image reconstruction to generate a high-resolution genome-wide 3D atlas of gene expression in the zebrafish embryo at three developmental stages. We also demonstrate that our technique is suitable for spatially-resolved differential expression analysis in wildtype and Gli3 mutant mouse forelimbs. Importantly, our method enables searching for genes that are expressed in specific spatial patterns without manual image annotation. We envision broad applicability of RNA tomography as an accurate and sensitive approach for spatially resolved transcriptomics in whole embryos and dissected organs. To generate spatially-resolved RNA-seq data for zebrafish embryos (shield stage, 10 somites, 15 somites, 18 somites) and mouse forelimbs (E10.5), we cryosectioned samples, extracted RNA from the individual sections, and amplified and barcoded mRNA using the CEL-seq protocol (Hashimshony et al., Cell Reports, 2012) with a few modifications. Libraries were sequenced on Illumina HiSeq 2500 using 50bp paired end sequencing. Selected zebrafish libraries were sequenced on MiSeq 250bp paired-end to improve 3' annotations.

ORGANISM(S): Danio rerio

SUBMITTER: Jan Philipp Junker

PROVIDER: E-GEOD-59873 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Vitamin D receptors (VDR) are abundantly expressed in developing zebrafish as early as 48 hours post-fertilization, and prior to the development of a mineralized skeleton, and mature intestine and kidney. We probed the role of VDR in zebrafish biology by examining changes in expression of RNA by whole transcriptome shotgun sequencing (RNA-seq) in fish treated with picomolar concentrations of the VDR ligand and hormonal form of vitamin D3, 1a,25-dihydroxyvitamin D3 (1a,25(OH)2D3). We observed significant changes in RNAs encoding proteins of fatty acid, amino acid, and xenobiotic metabolism pathways, and RNAs of transcription factors, leptin, peptide hormones, receptor-activator of NFkB ligand (RANKL), and calcitonin-like ligand receptor pathways. Early small, and subsequent massive changes in >10% of expressed cellular RNAs were observed. At day 2 (24h 1a,25(OH)2D3-treatment), only 5 RNAs were differentially expressed (hormone vs. vehicle). On day 4 (72h-treatment), 78 RNAs; on day 6 (120h-treatment) 1040 RNAs; and on day 7 (144h-treatment), 1755 RNAs were differentially expressed in response to 1a,25(OH)2D3. Fewer RNAs (n = 482) were altered in day 7 embryos treated for 24h with 1a,25(OH)2D3 vs. those treated with hormone for 144h. At 7 days, in 1a,25(OH)2D3-treated embryos, pharyngeal cartilage was larger and mineralization was greater. Changes in expression of RNAs for transcription factors, peptide hormones, and RNAs encoding proteins integral to fatty acid, amino acid, leptin, calcitonin-like ligand receptor, RANKL and xenobiotic metabolism pathways, demonstrate heretofore unrecognized mechanisms by which 1a,25(OH)2D3 functions in vivo in developing eukaryotes. Zebrafish embryos were obtained from mating of Segrest wild-type (SWT) parents under controlled barrier conditions, in the Mayo Clinic Zebrafish Core Facility, in Instant Ocean media . Zebrafish embryos (25-30) were placed in 20 mL embryo medium (pH 7.2) containing 1-phenyl-2-thiourea (PTU) (0.003% (w/v) and were maintained at 28-30 oC. At 24 hpf (1 day post fertilization, dpf), 10 microliters of 1a,25(OH)2D3 in ethanol was added to embryos maintained in 20 mL fresh embryo medium with PTU. The final concentration of 1a,25(OH)2D3 was 300 pM. Control zebrafish were treated with 10 microliters ethanol alone (vehicle controls). The medium containing either 300 pM 1a,25(OH)2D3 or vehicle was changed every 24 h . In experiment 1, at 2, 4, 6 and 7 dpf embryos/larvae were removed and immediately frozen at -80 0C for later RNA preparations. 25-30 embryos per set were used for preparation on RNA. At the same times, 7-12 embryos were fixed in 4% paraformaldehyde in 0.75 X DulbeccoM-bM-^@M-^Ys phosphate buffered saline (DPBS). In experiment 2, 6 dpf larvae were treated with 1a,25(OH)2D3 (300 pM) or vehicle for 24 h. RNA was prepared from three sets of larvae.

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Genome-wide RNA tomography in the zebrafish embryo

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