Project description: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.
Project description:The aim of our study was to characterize the genotypic and phenotypic extent of multi-locus imprinting disturbances. Therefore, we analyzed the DNA methylation pattern of 37 individuals with different DNA methylation disturbances. Of these 37 individuals 17 were previously diagnosed with a multi-locus methylation disturbance (MLID) and the remaing 20 were diagnosed with a typical single locus imprinting disorder (SLID). We compared the DNA methylation of these 37 individuals to the DNA methylation of 38 evaluable individuals born small for gestational age. Our analysis revealed 21/37 individuals with a multi-locus methylation disturbances, characterzied by an aberrant DNA methylation in more than one imprintend gene region. Validation analyses were performed by bisulfite-pyrosequencing in the two imprinted gene regions ZDBF2 and FAM50B. Our analyses revealed each one patient previously diagnosed with Temple- and Angelman syndrome to have MLID. Furthermore, we showed that many of the aberrantly methylated imprinted gene regions in patients with MLID are not associated with the so far known typical imprinting disorders.
Project description:DNA methylation is essential for embryonic development and implicated in the regulation of genomic imprinting. Genomic imprinting is established in the germline through parent-specific methylation of distinct cis-regulatory DNA sequences, called imprinting control regions (ICRs). Which factors bind to the opposing chromatin states at ICRs within the same nuclear environment was not systematically addressed. By using a proximity labelling approach with the methylation sensitive transcription factor ZFP57, we identified ATF7IP and other major components of the epigenetic maintenance machinery at ICRs.
Project description:Selective maintenance of genomic methylation imprints during pre-implantation development is required for parental origin-specific expression of imprinted genes. The Kruppel-like zinc finger protein ZFP57 acts as a factor necessary for maintaining the DNA methylation memory at multiple imprinting control regions (ICRs) in early mouse embryos and ES cells. Maternal-zygotic deletion of ZFP57 in mice presents a highly penetrant phenotype with no animals surviving to birth. In addition, several cases of human transient neonatal diabetes (TND) are associated with somatic mutations in ZFP57 coding sequence. Here we comprehensively map sequence-specific ZFP57 binding sites in an allele-specific manner using hybrid ES cell lines from reciprocal crosses between C57BL/6J and Cast/EiJ mice assigning allele specificity to approximately two thirds of all binding sites. While half of these are biallelic and include ERV targets, the rest show mono-allelic binding based either on parental-origin or on genetic background of the allele. Parental-origin allele-specific binding was methylation-dependent and mapped only to imprinted DMRs established in the germline (gDMRs). No binding was evident at secondary somatically-derived DMRs. ZFP57-bound gDMRs can predict imprinted gene expression and we identify new imprinted genes, including the Fkbp6 gene with a critical function in mouse male germ cell development. Genetic-background specific sequence differences also influence ZFP57 binding. We show that genetic variation that disrupts the consensus binding motif and its methylation is associated with mono-allelic expression of neighbouring genes. The work described here uncovers further roles for ZFP57 mediated regulation of genomic imprinting and identifies a novel mechanism for genetically determined mono-allelic gene expression. Input and Zfp57 CHiP-Seq profiles of hybrid Black6/Cast ES cells were generated by sequencing using the Illumina GAIIx platform.
Project description:We did RNA-seq analysis to compare gene expression profiles in mouse embryos with or without ZFP57. We also perfromed whole-genome bisulfite sequencing analysis (WGBS) for the Zfp57 mutant mouse embryos and control heterozygous embryos. We analyzed DNA methylation at the imprinting control regions (ICRs), differentially methylation regions (DMRs) and repetitive elements including LINE-1, LINE-2, SINE, LTR and IAP.
Project description:Genomic imprinting is controlled by CpG-rich regions (ICRs) acquiring differential methylation in the female and male germline and maintaining it in a parental origin-specific manner in somatic cells. Despite their expected mutation rate due to spontaneous deamination of methylated cytosines, ICRs maintain their CpG-richness and show conservation of CpG-bearing transcription binding sites in mammals. In order to gain further insights into the mechanisms of maintenance of methyl CpGs, we sought to identify the proteins interacting with the methylated allele of the ICRs, by determining the interactors of ZFP57 that recognizes a specific methylated ICR motif in mouse ESCs. Several proteins including factors involved in mRNA processing/splicing, chromatin organization, transcription and DNA repair were identified through a tagged approach coupled to LC–MS/MS analysis. The demonstration of the components of the post-replicative mismatch-repair (MMR) complex as ZFP57 interactors prompted us to investigate the DNA binding profile of MSH2 and MSH6 by chromatin immunoprecipitation and sequencing. We found that these proteins were enriched at the methylated allele of the ICRs and their binding was mediated by the ZFP57/KAP1 complex, suggesting that the MMR complex is recruited to these loci to preserve their genetic integrity.