Ontology highlight
ABSTRACT:
PROVIDER: PRJNA642258 | ENA |
REPOSITORIES: ENA
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Project description:Organisms invest significant effort into maintaining genome stability. However, in diverse groups of eukaryotes, portions or entire chromosomes are lost in early development or during sex determination, a process known as programmed DNA elimination. Little is known about how different segments of the genome are reproducibly retained and discarded during programmed DNA elimination. We tested the hypothesis that selective retention is mediated by regulation of centromere-mediated association of chromosome segments with the mitotic spindle. We report that on the holocentric chromosomes of the nematode Ascaris, the core centromeric histone CENP-A is localized differently in cells undergoing DNA elimination from those undergoing germline mitosis. Prior to DNA elimination, CENP-A is significantly reduced in chromosome regions that will be lost. CENP-A reduction in eliminated genomic regions leads to the absence of kinetochores and microtubule attachment sites necessary for chromosome segregation, and thus the loss of these DNA regions during Ascaris programmed DNA elimination. Our results show that holocentric chromosome organization in Ascaris is regulated and that changes in CENP-A deposition specify which portions of chromosomes will be eliminated during programmed DNA elimination. A total of 62 samples are analyzed. These include: (1). CENP-A ChIP-seq on 12 developmental stages with input and replicates (12 x 2 x 2 samples); (2). CENP-C ChIP-seq on 3 developmental stages with input and replicates (total 8 samples); and (3). Histone marks ChIP-seq with 6 samples
2016-07-15 | E-GEOD-76914 | biostudies-arrayexpress
Project description:Transcriptome analysis of B chromosome elimination in Aegilops speltoides
| PRJEB39517 | ENA
Project description:The stability of the genome is paramount to organisms. However, diverse eukaryotes carry out programmed DNA elimination in which portions or entire chromsomes are lost in early development or during sex determination. During early development of the parasitic nematode, Ascaris suum, 13% of the genome is eliminated. How different genomic segments are reproducibly retained or discarded is unknown. Here, we show that centromeric histone CENP-A localization plays a key role in this process. We show that Ascaris chromosomes are holocentric during germline mitoses, with CENP-A distributed along their length. Prior to DNA elimination in the four-cell embryo, CENP-A is significantly diminished in chromosome regions that will be lost. This leads to the absence of kinetochores and microtubule attachment sites necessary for chromosome segregation, resulting in loss of these regions upon mitosis. Our data suggest that changes in CENP-A localization specify which portions of chromosomes will be lost during programmed DNA elimination.
2016-07-15 | GSE76914 | GEO
Project description:In the ciliated protozoan Tetrahymena, de novo heterochromatin body formation is accompanied by programmed DNA elimination. We previously reported that dephosphorylation of the HP1-like protein Pdd1p is required for the formation of heterochromatin bodies during the process of programmed DNA elimination in the ciliated protozoan Tetrahymena. Here, we show that the heterochromatin body component Jub4p is required for Pdd1p phosphorylation, heterochromatin body formation and DNA elimination. Moreover, our analyses of unphosphorylatable Pdd1p mutants demonstrate that Pdd1p phosphorylation is required for heterochromatin body formation and DNA elimination, while it is dispensable for local heterochromatin assembly. Therefore, both phosphorylation and the following dephosphorylation of Pdd1p are necessary to facilitate the formation of heterochromatin bodies. We suggest that Jub4p-mediated phosphorylation of Pdd1p creates a chromatin environment that is a prerequisite for subsequent heterochromatin body assembly and DNA elimination. New macronuclei (MACs) of exconjugants were isolated from wild-type and various mutant cells at 12 hpm (hours post-mixing), sheared chromatin was immunoprecipitated andprecipitated DNA was analyzed by high-throughput sequencing
2016-07-15 | E-GEOD-83249 | biostudies-arrayexpress
Project description:Programmed DNA elimination is a developmentally regulated process leading to the reproducible loss of specific genomic sequences. DNA elimination occurs in unicellular ciliates and a variety of metazoans, including invertebrates and vertebrates. In metazoa, DNA elimination typically occurs in somatic cells during early development, leaving the germline genome intact. Reference genomes for metazoa that undergo DNA elimination are not available. Here, we generated germline and somatic reference genome sequences of the DNA eliminating pig parasitic nematode Ascaris suum and the horse parasite Parascaris univalens. In addition, we carried out in-depth analyses of DNA elimination in the parasitic nematode of humans, Ascaris lumbricoides, and the parasitic nematode of dogs, Toxocara canis. Our analysis of nematode DNA elimination reveals that in all species, repetitive sequences (that differ among the genera) and germline-expressed genes (approximately 1000-2000 or 5%-10% of the genes) are eliminated. Thirty-five percent of these eliminated genes are conserved among these nematodes, defining a core set of eliminated genes that are preferentially expressed during spermatogenesis. Our analysis supports the view that DNA elimination in nematodes silences germline-expressed genes. Over half of the chromosome break sites are conserved between Ascaris and Parascaris, whereas only 10% are conserved in the more divergent T. canis. Analysis of the chromosomal breakage regions suggests a sequence-independent mechanism for DNA breakage followed by telomere healing, with the formation of more accessible chromatin in the break regions prior to DNA elimination. Our genome assemblies and annotations also provide comprehensive resources for analysis of DNA elimination, parasitology research, and comparative nematode genome and epigenome studies.
2017-08-15 | GSE99524 | GEO
Project description:Programmed DNA elimination is a developmentally regulated process leading to the reproducible loss of specific genomic sequences. DNA elimination occurs in unicellular ciliates and a variety of metazoans, including invertebrates and vertebrates. In metazoa, DNA elimination typically occurs in somatic cells during early development, leaving the germline genome intact. Reference genomes for metazoa that undergo DNA elimination are not available. Here, we generated germline and somatic reference genome sequences of the DNA eliminating pig parasitic nematode Ascaris suum and the horse parasite Parascaris univalens. In addition, we carried out in-depth analyses of DNA elimination in the parasitic nematode of humans, Ascaris lumbricoides, and the parasitic nematode of dogs, Toxocara canis. Our analysis of nematode DNA elimination reveals that in all species, repetitive sequences (that differ among the genera) and germline-expressed genes (approximately 1000-2000 or 5%-10% of the genes) are eliminated. Thirty-five percent of these eliminated genes are conserved among these nematodes, defining a core set of eliminated genes that are preferentially expressed during spermatogenesis. Our analysis supports the view that DNA elimination in nematodes silences germline-expressed genes. Over half of the chromosome break sites are conserved between Ascaris and Parascaris, whereas only 10% are conserved in the more divergent T. canis. Analysis of the chromosomal breakage regions suggests a sequence-independent mechanism for DNA breakage followed by telomere healing, with the formation of more accessible chromatin in the break regions prior to DNA elimination. Our genome assemblies and annotations also provide comprehensive resources for analysis of DNA elimination, parasitology research, and comparative nematode genome and epigenome studies.
2017-08-15 | GSE99523 | GEO
Project description:Programmed minichromosome elimination
| PRJNA326452 | ENA
Project description:In the ciliated protozoan Tetrahymena, de novo heterochromatin body formation is accompanied by programmed DNA elimination. Here, we show that the novel heterochromatin body component Jub1p promotes heterochromatin body formation and dephosphorylation of the Heterochromatin Protein 1 (HP1)-like protein Pdd1p. Through the identification and mutagenesis of the phosphorylated residues of Pdd1p, we demonstrate that Pdd1p dephosphorylation promotes the electrostatic interaction between Pdd1p and RNA in vitro and heterochromatin body formation in vivo. We therefore suggest that heterochromatin bodies are assembled by the Pdd1p-RNA interaction. Jub1p and Pdd1p dephosphorylation are required for heterochromatin body formation and DNA elimination but not for local heterochromatin assembly, indicating that heterochromatin body of itself plays an essential role in DNA elimination. New macronuclei (MACs) of exconjugants were isolated from wild-type different mutant cells at 12 hpm, shared chromatin was immunoprecipitated and precipitated DNA was analyzed by high-throughput sequencing.
2015-12-10 | E-GEOD-70081 | biostudies-arrayexpress
Project description:<p>Chronic lymphocytic leukemia (CLL) is a frequent B-cell malignancy characterized by recurrent somatic chromosome alterations and a low level of point mutations. Here we present single nucleotide polymorphism (SNP) microarray analyses of a single CLL patient over 29-years of observation and treatment, and transcriptome and whole genome sequencing at selected timepoints. We identified chromosome alterations of 13q14-, 6q- and 12q+ in early cell clones, elimination of clonal populations following therapy, and subsequent appearance of a clone containing trisomy 12 and a chromosome 10 copy neutral loss of heterogeneity (LOH) that marks a major population dominant at death. Serial single cell RNA sequencing revealed elevated mRNA expression of the FOS, JUN and KLF4 genes just before the appearance of acute disease requiring therapy. This gene expression pattern became undetectable following therapy, but reoccurred following relapse. Transcriptome evolution indicates that complex expression changes occur over time. In conclusion, CLL can evolve gradually during indolent phases, and undergo rapid changes following therapy. </p>
| phs001181 | dbGaP
Project description:Internal eliminated sequences elimination
| PRJNA416874 | ENA