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A Novel Approach Identifies New Differentially Methylated Regions (DMRs) Associated with Imprinted Genes

ABSTRACT: Imprinted genes are critical for normal human growth and neurodevelopment. We developed a strategy to identify new DNA differentially methylated regions (DMRs), a hallmark of imprinted genes. Using genome-wide methylation profiling, candidate DMRs were selected by identifying CpGs with putative allelic differential methylation in normal biparental tissues. In parallel, we looked for parent of origin-specific DNA methylation patterns in paternally derived human androgenetic complete hydatidiform mole (AnCHM), and maternally derived mature cystic ovarian teratoma (MCT). Using this approach, we found known DMRs associated with imprinted genomic regions as well as new DMRs for known imprinted genes, NAP1L5 and ZNF597. Most importantly, novel candidate imprinted genes were identified. The paternally methylated DMR for one candidate, AXL, a receptor tyrosine kinase, was validated by methylation analyses in humans. Further validation in mouse embryos showed that Axl was expressed preferentially from the maternal allele in a DNA methylation–dependent manner.

ORGANISM(S): Homo sapiens

PROVIDER: GSE22091 | GEO | 2011/01/26

SECONDARY ACCESSION(S): PRJNA128825

REPOSITORIES: GEO

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Project description:Genomic imprinting is a mechanism in which the expression of genes varies depending on their parent-of-origin. Imprinting occurs through differential DNA methylation and histone modifications on the two parental alleles, with most imprinted genes marked by CpG-rich differentially methylated regions (DMRs). DNA methylation profiling in cases of uniparental disomy (UPD) provides a unique system permitting the study of DNA derived from a single parent (PMID: 20631049). Approximately 70 human imprinted genes have been described, and imprinted loci have been associated with diseases such as diabetes and cancer. We profiled parent of origin DNA methylation marks to find novel imprinted loci. Methods: We have an unprecedented collection of whole blood DNA from XX patients with UPD covering 18 different chromosomes, allowing for the efficient detection of DMRs associated with imprinted genes for 84% of the human genome. Our study is complimented with Ovarian Teratoma DNA (maternal DNA) and Complete hydatidiform Mole (paternal DNA). DNA methylation was profiled using Illumina Infinium 450K Methylation BeadArrays. Imprinted DMRs were defined by sites at which the maternal and paternal methylation levels diverged significantly from the biparental average. We confirmed novel DMRs by bisulfite sequencing of informative trios and SequenomEpiTYPER assays. Allelic specific gene expression studies were also performed by RNA sequencing in independent biparental controls. Findings: Our results provide for the first comprehensive map of the human imprintome, doubling the number of known imprinted regions. We identified a total of 71 DMRs, 41 of which were novel. 27 novel DMRs were maternally methylated and 14 were paternally methylated. We identified DMRs on chromosomes 5, 21 and 22 previously considered devoid of imprinting, highlighting potential parent-of-origin effects in chromosomal aneuploidies such as Down syndrome. We also found DMRs in genes associated with Schizophrenia and epilepsy. Interpretation: Our data provide the first comprehensive genome-wide map of imprinted sites in the human genome, and provide novel insights into potential parent-of-origin effects in human disorders. 66 UPD samples analyzed in total, From each individual, whole bllod DNA was extracted and global DNA methylation levels were assessed using Illumina Infinium HumanMethylation450 BeadChip.

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A Novel Approach Identifies New Differentially Methylated Regions (DMRs) Associated with Imprinted Genes

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