Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Silencing of Germline-Expressed Genes by DNA Elimination in Somatic Cells

ABSTRACT: Chromatin diminution is the programmed elimination of specific DNA sequences during development. It occurs in diverse species, but the function(s) of diminution and the specificity of sequence loss remain largely unknown. Diminution in the nematode Ascaris suum occurs during early embryonic cleavages and leads to the loss of germline genome sequences and the formation of a distinct genome in somatic cells. We found that M-bM-^HM-<43 Mb (M-bM-^HM-<13%) of genome sequence is eliminated in A. suum somatic cells, including M-bM-^HM-<12.7 Mb of unique sequence. The eliminated sequences and location of the DNA breaks are the same in all somatic lineages from a single individual and between different individuals. At least 685 genes are eliminated. These genes are preferentially expressed in the germline and during early embryogenesis. We propose that diminution is a mechanism of germline gene regulation that specifically removes a large number of genes involved in gametogenesis and early embryogenesis. To profile the tissue expression of all A. suum genes, we used 8 different developmental stages/tissues of A. suum, including testis, ovary, embryo, larvae, intestine, muscle, male carcass and female carcass. In this submission there are 10 samples: 3 for early embryos (24hr, 46hr and 64hr) and the other 7 for testis, ovary, larvae, intestine, muscle, male carcass and female carcass. For each sample, 200 ug of total RNA was used for poly(A) selection and 200 ng of poly(A)+ RNA was used to make the cDNA libraries using standard Illumina protocol.

ORGANISM(S): Ascaris suum

SUBMITTER: Jianbin Wang

PROVIDER: E-GEOD-38470 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Silencing of germline-expressed genes by DNA elimination in somatic cells.

Wang Jianbin J Mitreva Makedonka M Berriman Matthew M Thorne Alicia A Magrini Vincent V Koutsovoulos Georgios G Kumar Sujai S Blaxter Mark L ML Davis Richard E RE

Developmental cell 20121101 5

Chromatin diminution is the programmed elimination of specific DNA sequences during development. It occurs in diverse species, but the function(s) of diminution and the specificity of sequence loss remain largely unknown. Diminution in the nematode Ascaris suum occurs during early embryonic cleavages and leads to the loss of germline genome sequences and the formation of a distinct genome in somatic cells. We found that ∼43 Mb (∼13%) of genome sequence is eliminated in A. suum somatic cells, inc ...[more]

PMID: 23123092

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Project description:A long-standing view of development is that transcription is silenced in the oocyte until early divisions in the embryo. The point at which major transcription is reactivated varies in different organisms, but is usually after the 2-cell stage. However, this model may not be universal. We used RNA-seq and exploited the protracted development of the parasitic nematode Ascaris suum, to provide a comprehensive time course of mRNA expression, degradation, and translation during early development. Surprisingly, we find that ~4,000 genes are transcribed prior to pronuclear fusion and in the 1-4 cell embryos. Intriguingly, we do not detect maternal contribution of many orthologs of maternal C. elegans mRNAs, but instead find these are newly transcribed in the A. suum zygote prior to pronuclear fusion. Ribosome profiling demonstrates that, in general, early embryonic mRNAs are not stored for subsequent translation, but are directly translated following their synthesis. The role of maternally contributed and zygotically transcribed genes differs between the nematodes A. suum and C. elegans despite the fact that the two nematodes appear to exhibit highly similar morphological patterns during early development. Our study indicates that major transcription can occur immediately after fertilization and prior to pronuclear fusion in metazoa, suggesting that newly transcribed genes appear to drive A. suum early development. Furthermore, the mechanisms used for controlling the timing of the expression of key conserved genes has been altered between the two nematodes, illustrating significant plasticity in the regulatory networks that play important roles in developmental outcomes in nematodes. A total of 28 samples are used for this study. The RNAs for the library construction are derived from 0.5 M-bM-^@M-^S 1 ml of synchronized embryo stages corresponding to a minimum of 0.5 billion embryos derived from > 1,000 female worms. The RNAs for polysome analysis are from pooled fractions of polysome gradient. For each sample, the amount of RNA for all polysome fractions is equivalent to the total RNA from the sample. Thus, the data from polysome profiling and RNA transcriptomes are considered as biological replicates. The level of the RNAs between each neighboring stages during development are considered as the reference for each other. Different sequencing strategies were applied for multiple libraries.

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Dataset Information

Silencing of Germline-Expressed Genes by DNA Elimination in Somatic Cells

Publications

Silencing of germline-expressed genes by DNA elimination in somatic cells.

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