Project description:Genomic imprinting is regulated by parental-specific epigenetic marks that differentiate between maternal and paternal chromosomes. Despite identical DNA sequence, the presence or absence of DNA methylation leads to the establishment of two distinct epigenetic states at Imprinting Control Regions (ICR). Here we combine targeted epigenome engineering to generate ectopic loci in the mouse embryonic stem cell genome that recapitulate the epigenetic properties of ICRs. We describe these ectopic ICRs as strong cis-regulatory sequences that can adopt and memorise one of two opposing epigenetic states, dependent of pre-imposed DNA methylation. This bistability is unique to ICRs and enabled us to systematically study the genetic and epigenetic determinants required for creating and maintaining the observed states. Through sequence manipulation we show that the ICR DNA sequence confers autonomy of ICRs and is required for creating epigenetic bistability. Genetic screens using DNA-methylation-sensitive reporters identify key components involved in regulating maintenance of epigenetic states. Besides DNMT1, UHRF1 and ZFP57, we identify novel factors that prevent switching between methylated and unmethylated states and validate two of these candidates, ATF7IP and ZMYM2, to be important for epigenetic memory at ICRs. In summary we show that the DNA sequence of ICRs provides the prerequisite for establishment of two distinct epigenetic states, while DNA and histone modifications ensure their stable propagation.
Project description:Genomic imprinting is regulated by parental-specific epigenetic marks that differentiate between maternal and paternal chromosomes. Despite identical DNA sequence, the presence or absence of DNA methylation leads to the establishment of two distinct epigenetic states at Imprinting Control Regions (ICR). Here we combine targeted epigenome engineering to generate ectopic loci in the mouse embryonic stem cell genome that recapitulate the epigenetic properties of ICRs. We describe these ectopic ICRs as strong cis-regulatory sequences that can adopt and memorise one of two opposing epigenetic states, dependent of pre-imposed DNA methylation. This bistability is unique to ICRs and enabled us to systematically study the genetic and epigenetic determinants required for creating and maintaining the observed states. Through sequence manipulation we show that the ICR DNA sequence confers autonomy of ICRs and is required for creating epigenetic bistability. Genetic screens using DNA-methylation-sensitive reporters identify key components involved in regulating maintenance of epigenetic states. Besides DNMT1, UHRF1 and ZFP57, we identify novel factors that prevent switching between methylated and unmethylated states and validate two of these candidates, ATF7IP and ZMYM2, to be important for epigenetic memory at ICRs. In summary we show that the DNA sequence of ICRs provides the prerequisite for establishment of two distinct epigenetic states, while DNA and histone modifications ensure their stable propagation.
Project description:Genomic imprinting is regulated by parental-specific epigenetic marks that differentiate between maternal and paternal chromosomes. Despite identical DNA sequence, the presence or absence of DNA methylation leads to the establishment of two distinct epigenetic states at Imprinting Control Regions (ICR). Here we combine targeted epigenome engineering to generate ectopic loci in the mouse embryonic stem cell genome that recapitulate the epigenetic properties of ICRs. We describe these ectopic ICRs as strong cis-regulatory sequences that can adopt and memorise one of two opposing epigenetic states, dependent of pre-imposed DNA methylation. This bistability is unique to ICRs and enabled us to systematically study the genetic and epigenetic determinants required for creating and maintaining the observed states. Through sequence manipulation we show that the ICR DNA sequence confers autonomy of ICRs and is required for creating epigenetic bistability. Genetic screens using DNA-methylation-sensitive reporters identify key components involved in regulating maintenance of epigenetic states. Besides DNMT1, UHRF1 and ZFP57, we identify novel factors that prevent switching between methylated and unmethylated states and validate two of these candidates, ATF7IP and ZMYM2, to be important for epigenetic memory at ICRs. In summary we show that the DNA sequence of ICRs provides the prerequisite for establishment of two distinct epigenetic states, while DNA and histone modifications ensure their stable propagation.
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:Genomic imprinting is an epigenetic mechanism whereby a subset of genes, called imprinted genes, show parent-of-origin-dependent monoallelic expression. Most imprinted genes are regulated by allele-specific DNA methylation at differentially methylated regions (DMRs). Although major imprinted genes and DMRs have already been identified in human and mouse, information on genomic imprinting is sporadic and limited in other mammalian species due to the cost and technical difficulties of genome-wide allele-specific gene expression and DNA methylation analyses. Here we propose two strategies to predict DMRs from whole-genome bisulfite sequencing (WGBS) data: one is based on conservation and the other is on germline DNA methylation patterns. Both strategies do not require genotype information and predict DMRs with high sensitivity and low background. We applied these strategies to human, rhesus, mouse and cow and estimated the evolutionary trajectory of individual DMRs. These analyses suggest that various factors, including CpG density, germline methylation and sequence-specific DNA binding proteins, may contribute to species-specific differences in genomic imprinting. Our strategies will facilitate cross-species comparison of genomic imprinting and identification of novel DMRs.
Project description:Genomic imprinting is regulated by parental-specific DNA methylation of imprinting control regions (ICRs). Despite an identical DNA sequence, ICRs can exist in two distinct epigenetic states that are memorized throughout unlimited cell divisions and reset during germline formation. Here, we systematically study the genetic and epigenetic determinants of this epigenetic bistability. By iterative integration of ICRs and related DNA sequences to an ectopic location in the mouse genome, we first identify the DNA sequence features required for maintenance of epigenetic states in embryonic stem cells. The autonomous regulatory properties of ICRs further enabled us to create DNA-methylation-sensitive reporters and to screen for key components involved in regulating their epigenetic memory. Besides DNMT1, UHRF1 and ZFP57, we identify factors that prevent switching from methylated to unmethylated states and show that two of these candidates, ATF7IP and ZMYM2, are important for the stability of DNA and H3K9 methylation at ICRs in embryonic stem cells.