Unknown,Transcriptomics,Genomics,Proteomics

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Methylation profiling of human pediatric acute lymphoblastic leukemia

ABSTRACT: Samples from 20 children with B-cell precursor ALL, comprising ten with high hyperdiploidy and ten with the ETV6/RUNX1 fusion, were included in the study. Four Âµg of methylated and input fraction DNA were analyzed with a classic MeDIP assay and subsequent microarray hybridization using the NimbleGen CpG Island-Plus-Promoter Array (Roche NimbleGen, Madison, WI).

This array platform covers all 28,226 UCSC-annotated CpG islands and promoter regions for all RefSeq genes, including 385,000 probes of 50-75mer length per array, with an upstream and downstream promoter tiling of 800 bp and 200 bp, respectively. Signal intensity data were extracted from the scanned images. Each feature on the array has a corresponding log2 ratio, which is the ratio of the input signals for the methylated DNA and the input fraction DNA. The log2 ratio was scaled in order to center the ratio data around zero by subtracting the bi-weight mean for the log2 ratio values for all features on the array from each log2 ratio value. A modified ACME algorithm, where a fixed-length window (750 bp) is placed around each consecutive probe, and the one-sided Kolmogorov-Smirnov test were then applied on the scaled log2 ratio data to determine whether the probes were drawn from a significantly more positive distribution (peak) of intensity log2 ratios than the other probes in the array. The resulting score for each probe is the -log10 p-value from the windowed Kolmogorov-Smirnov test around that probe. Peak data were generated by searching for probes above a p-value minimum cut-off (-log10) of 2.

Peaks within 500 bp of each other were merged. Each annotated gene was subsequently searched for peaks appearing in a specified promoter region around the transcription start site. The region searched was design-specific, spanning from 5 kb upstream to 1 kb downstream of the transcription start site. Genes that had at least two probes with peaks above the p-value minimum cut-off were considered to have significant CpG island methylation scores for hypermethylation.

ORGANISM(S): Homo sapiens

SUBMITTER: Josef Davidsson

PROVIDER: E-MTAB-144 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Phenotypic plasticity, the ability of one genotype to express different phenotypes in response to changing environmental conditions, is one of the most common phenomena characterising the living world and is not only relevant for the ecology but also for the evolution of species. Daphnia, the waterflea, is a textbook example for predator induced phenotypic plastic defences including changes in life-history, behaviour and morphology. However, the analysis of molecular mechanisms underlying these inducible defences is still in its early stages. We exposed Daphnia magna to chemical cues of the predator Triops cancriformis to identify key processes underlying plastic defensive trait formation. D. magna is known to develop an array of morphological changes in the presence of T. cancriformis including changes of carapace morphology and cuticle hardening. To get a more comprehensive idea of this phenomenon, we studied four different genotypes originating from habitats with different predation history, reaching from predator-free to temporary habitats containing T. cancriformis. We analysed the morphologies as well as proteomes of predator-exposed and control animals. Three genotypes showed morphological changes when the predator was present. Using a high-throughput proteomics approach, we found 294 proteins which were significantly altered in their abundance after predator exposure in a general or genotype dependant manner. Proteins connected to genotype dependant responses were related to the cuticle, protein synthesis and calcium binding whereas the yolk protein vitellogenin increased in abundance in all genotypes, indicating their involvement in a more general response. Furthermore, genotype dependant responses at the proteome level correlated well with local adaptation to Triops predation. Altogether, our study provides new insights concerning genotype dependant and general molecular processes involved in predator-induced phenotypic plasticity in D. magna.

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Methylation profiling of human pediatric acute lymphoblastic leukemia

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