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Multi-locus imprinting disturbances in a family harboring a ZFP57 truncation

ABSTRACT: We previously reported a child with transient neonatal diabetes mellitus (TNDM), who upon molecular diagnosis was homozygous for a one base-pair deletion in ZFP57, inheriting the mutations from both heterozygous parents. Methylation profiling at diagnosis revealed severe hypomethylation at PLAGL1 and mosaic loss-of-methylation (LOM) at GRB10, NAP1L5 and GNAS-XL DMRs. Some years after the first child, a second sibling was born with a comparable clinical presentation. Upon molecular investigation this child was shown to have the same homozygous deletion. Using Illumina Infinium BeadChip arrays, we confirmed similar hypomethylated signatures at ubiquitous imprinted DMRs. To further characterize the stability of the imprinting defects and understand the role of this mutation in tissue-specific mosaicism, we hybridised buccal-derived DNA and a second leukocyte sample from first child to the HumanMethylationEPIC arrays. When comparing the two blood-derived samples, we observed that the hypomethylation signature is stable over time with the PLAGL1 DMR being the most severely affected, consistent with this being the disease-causing locus. Furthermore, when comparing the leukocyte and buccal samples, the same imprinted DMRs were affected to a similar extent.

ORGANISM(S): Homo sapiens

PROVIDER: GSE149568 | GEO | 2020/11/27

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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Multi-locus imprinting disturbances in a family harboring a ZFP57 truncation

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