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Disturbed methylation at multiple imprinted loci in iPSCs derived from ICF1 patients during reprogramming

ABSTRACT: DNA methylation perturbations have been a hallmark of Immunodeficiency, Centromeric instability, Facial anomalies type I (ICF1) syndrome. The early developmental abnormalities due to DNMT3B deficiency accounts for genome-wide methylation defects that have been addressed frequently in many studies. Biallelic hypomorphic DNMT3B mutations cause the ICF1 syndrome. We have investigated the role of DNMT3B in mediating methylation at imprinted loci by employing induced pluripotent stem cells (iPSC) lines derived from ICF1 patients and their derivative strains in which the DNMT3B mutations were corrected by CRISPR/Cas9 technology. For ICF1 syndrome, skin fibroblasts derived DNA were also included for comparison purposes. By employing a whole-genome array-based approach, we observed a strong hypomethylation at a subset of gDMRs and sDMRs. However, these did not fully recover methylation despite most of the other hypomethylated CpGs in the genome reverted to their epigenetic state in the corrected iPSC clones. Loss of imprinted methylation in the ICF iPSCs was accompanied by increased levels of histone H3K4 trimethylation and in some cases gene activation, which were only partially reversed upon correction. Overall our study provides a comprehensive analysis of the role of DNMT3B activity in genomic imprinting maintenance in human somatic cells and indicates a molecular mechanism explaining why imprinting defects are resistant to correction.

ORGANISM(S): Homo sapiens

PROVIDER: GSE198705 | GEO | 2023/11/28

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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Disturbed methylation at multiple imprinted loci in iPSCs derived from ICF1 patients during reprogramming

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