Project description:To improve our knowledge on this largely unknown phenomenon, and to study the role of MeCP2 in RMAE, we compared RMA gene expression profiles in clonal cell cultures expressing wild-type MeCP2 versus mutant MeCP2 from a RTT patient carrying a pathogenic non-sense variant.
Project description:Genes are generally thought to be expressed from both alleles. There are some exceptions, including Random monoallelic expression (RME), even though its extent is still somewhat debated. We assessed whether and how some autosomal genes that we previously identified as being RME are prone to persistent and stable monoallelic expression. Not only do we confirm the occurrence of RME at large frequencies, our results also reveal unforeseen modes of allelic expression,that appear to be gene specific and epigenetically regulated. This non-canonical allelic regulation has large physiological and pathological implications and represents novel therapeutic perspectives.
Project description:To ensure dosage compensation between the sexes, one randomly chosen X chromosome is silenced in each female cell in the process of X-chromosome inactivation (XCI). XCI is a model for cellular decision making and epigenetic gene regulation. The random cell-autonomous nature of XCI however has so far prevented its chromosome-wide investigation in its endogenous context without genetic perturbation. Here we use allele-specific single-cell RNA-sequencing to assess the onset of random XCI with high temporal resolution in differentiating mouse embryonic stem cells, and develop dedicated analysis approaches. We find that XCI is initiated on both chromosomes in a subset of cells, but reverted to the final mono-allelic state once gene silencing is established. By exploiting the heterogeneity of XCI onset, we identify Nanog as its main trigger and discover additional genes that might control upregulation of Xist, the master regulator of XCI. Finally, we show that genetic variation between different mouse strains modulates the XCI process at multiple levels, and validate these findings through an orthogonal experimental approach. We thus draw a detailed picture of how XCI is initiated and the experimental and computational strategies we have developed here will now allow us to profile random XCI in more physiological contexts, including primary human cells in vivo.
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.
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.