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A genome-wide search for epigenetically regulated genes in zebra finch using MethylCap-seq and RNA-seq

ABSTRACT: DNA methylation is tightly linked with gene expression regulation and has long been regarded a stable epigenetic mark in postmitotic cells. However, it recently became clear that postnatal brains appear to show stimulus-induced de novo CpG methylation or active demethylation related to neuronal plasticity. Due to striking homologies between the brains of birds and mammals, songbirds, especially the zebra finch, propose an attractive model for investigating the genome-wide DNA methylation profile and DNA methylation reconfiguration during brain development. In order to obtain a first genome-wide compendium of genes under putative DNA methylation control, we performed MethyCap-seq experiments on two recently cultured zebra finch cell lines, G266 and ZFTMA, also upon AZA-induced demethylation. First, the MethylCap-seq methodology in zebra finch was validated by comparison with RRBS generated data. Subsequently, quantitative analysis identified 30,700 significantly demethylated loci upon AZA-treatment. Further examination revealed enrichment of these regions in exons and promoters. To assess the influence of methylation on gene expression, RNA-seq experiments were performed. Comparison of the RNA-seq and MethylCap-seq results showed that at least 357 of the 3,457 AZA-upregulated genes are putatively regulated by methylation in the promoter region, for which a pathway analysis showed obvious enrichment for neurological networks. A subset of genes was validated using qPCR and CpG pyrosequencing. To our knowledge, this study provides the first genome-wide DNA methylation map of the zebra finch genome as well as a comprehensive set of genes of which transcription is under putative methylation control.

ORGANISM(S): Taeniopygia guttata

PROVIDER: GSE61060 | GEO | 2015/12/10

SECONDARY ACCESSION(S): PRJNA260172

REPOSITORIES: GEO

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Project description:DNA methylation is tightly linked with gene expression regulation and has long been regarded a stable epigenetic mark in postmitotic cells. However, it recently became clear that postnatal brains appear to show stimulus-induced de novo CpG methylation or active demethylation related to neuronal plasticity. Due to striking homologies between the brains of birds and mammals, songbirds, especially the zebra finch, propose an attractive model for investigating the genome-wide DNA methylation profile and DNA methylation reconfiguration during brain development. In order to obtain a first genome-wide compendium of genes under putative DNA methylation control, we performed MethyCap-seq experiments on two recently cultured zebra finch cell lines, G266 and ZFTMA, also upon AZA-induced demethylation. First, the MethylCap-seq methodology in zebra finch was validated by comparison with RRBS generated data. Subsequently, quantitative analysis identified 30,700 significantly demethylated loci upon AZA-treatment. Further examination revealed enrichment of these regions in exons and promoters. To assess the influence of methylation on gene expression, RNA-seq experiments were performed. Comparison of the RNA-seq and MethylCap-seq results showed that at least 357 of the 3,457 AZA-upregulated genes are putatively regulated by methylation in the promoter region, for which a pathway analysis showed obvious enrichment for neurological networks. The ZF exon-arrays analysis validated the RNA-seq expression result for 75% and 62%, of the down and up-regulated genes, respectively. A subset of genes was validated also using qPCR and CpG pyrosequencing. To our knowledge, this study provides the first genome-wide DNA methylation map of the zebra finch genome as well as a comprehensive set of genes of which transcription is under putative methylation control Within the overall project, we performed a set of microarrays to validate RNAseq data (Series accession number GSE61060) . DMSO- and AZA-treated zebra finch cell lines, i.e. G266 and ZFTMA. ChipInspector carries out significance analysis on the single probe level. Normalized probe set level data not provided for individual Sample records. Processed data is available on Series record.

Project description:Purpose: To investigate the role of DNA methylation in human uterine leiomyoma tumorigenesis, we profiled genome-wide DNA methylation patterns of leiomyoma cells (LM) and adjacent normal myometrial cells (MM) treated with or without DNA methylation inhibitor 5-Aza. Methods: Primary cells were isolated from fresh uterine myometrium or leiomyoma tissue. Cells were treated with vehicle (DMSO) or 5 µM 5’-aza for 96h with medium refreshed every 24h. Genomic DNA was extracted from LM and MM cells using DNeasy Blood and Tissue Kit (Qiagen, 69504) and fragmented to 300-500bp using Covaris M220. Methylated DNA fragments were captured using the MethylCap Kit (Diagenode, C02020010). Next-generation sequencing libraries were prepared using the KAPA Hyper Prep Kit (KAPA Biosystems, KK8502) and KAPA Single-Indexed Adapter Kit (KAPA Biosystems, KK8710). Libraries were sequenced under 75bp paired-end sequencing format. Sequences were aligned to the hg19 reference genome using Bowtie2. Histone style peak calling, differential binding analysis (getDifferentialPeaks) and motif analysis were performed using Homer under default settings. Differentily methylated regions (DMRs) were detected with a fold enrichment over background tag count ≥4 and poisson enrichment p-value over background tag count <0.0001. Differential DNA methylation between MM and LM (with or without treatment) at select regions were validated through qPCR. Results: More than 100,000 methyalted regions were detected in each sample. We discovered 21,086 DMRs between MM and LM cells under basal (vehicle treated) condition. In cells treated with 5-aza, we detected 8811 DMRs between MM and LM. We compared the genomic context of DMRs identified by MethylCap-Seq with the probe distribution of the HM450 array and detected large differences between these two methods. For example, 44.23% of DMR were located in intergenic regions by MethylCap-Seq, which was drastically higher than the percentage of HM450 array probes located in intergenic regions Downstream network enrichment analysis and motif analysis indicated that DMR-associated genes and regions are crucial for the tumor progression and hormone responsiveness of LM. Conclusions: Our study represents the detailed analysis of differential DNA methyaltion profiles between MM and LM using MethylCap-seq. Our results showed a more comprehensive evaluation of DNA methyaltion landscapes of MM and LM compared with previous array based analysis. We conclude that DNA methylation plays a crucial role in hormone-dependent LM tumorigenesis.

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A genome-wide search for epigenetically regulated genes in zebra finch using MethylCap-seq and RNA-seq

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