Project description:Multiple regulatory layers influence allele-specific expression (ASE), particularly through sequence-dependent and parent-of-origin-dependent mechanisms at the transcriptional level. However, little is known about allele-specific gene regulation at the post-transcriptional level. Here, we conduct transcriptome-wide analysis of allele-specific m6A in mice. Using early postnatal cerebellum and cerebrum samples from reciprocal crosses of two divergent mouse strains, we employed quantitative m6A assays to measure allelic differences in m6A at single-base resolution. Our study reveals widespread sequence-dependent allelic imbalance in m6A methylation, identifying thousands of allele-specific m6A (ASm6A) sites with statistically significant and reproducible allelic methylation differences across diverse samples. We find evidence of potential cis-regulatory variants within 50-nt flanking regions of these ASm6A sites, with the highest enrichment at the motif positions. Intriguingly, we detect parental effects on allelic methylation across m6A sites exhibiting parent-of-origin-dependent ASE. For both sequence- and parent-of-origin-dependent allelic m6A methylation, we observe opposing allelic preferences between methylation and expression, suggesting a potential role of ASm6A in regulating ASE through negative effects on gene expression. Overall, our findings reveal that both cis-acting and parent-of-origin effects influence ASm6A, offering new insights into post-transcriptional mechanisms of ASE regulation.
Project description:Multiple regulatory layers influence allele-specific expression (ASE), particularly through sequence-dependent and parent-of-origin-dependent mechanisms at the transcriptional level. However, little is known about allele-specific gene regulation at the post-transcriptional level. Here, we conduct transcriptome-wide analysis of allele-specific m6A in mice. Using early postnatal cerebellum and cerebrum samples from reciprocal crosses of two divergent mouse strains, we employed quantitative m6A assays to measure allelic differences in m6A at single-base resolution. Our study reveals widespread sequence-dependent allelic imbalance in m6A methylation, identifying thousands of allele-specific m6A (ASm6A) sites with statistically significant and reproducible allelic methylation differences across diverse samples. We find evidence of potential cis-regulatory variants within 50-nt flanking regions of these ASm6A sites, with the highest enrichment at the motif positions. Intriguingly, we detect parental effects on allelic methylation across m6A sites exhibiting parent-of-origin-dependent ASE. For both sequence- and parent-of-origin-dependent allelic m6A methylation, we observe opposing allelic preferences between methylation and expression, suggesting a potential role of ASm6A in regulating ASE through negative effects on gene expression. Overall, our findings reveal that both cis-acting and parent-of-origin effects influence ASm6A, offering new insights into post-transcriptional mechanisms of ASE regulation.
Project description:Base-resolution analyses of parent-of-origin and sequence dependent allele specific DNA methylation in the mouse genome (ChIP-seq and Methyl-seq)
Project description:Allele specific DNA methylation (ASM) is crucial for genomic imprinting and mammalian development. Here we present a base-resolution, genome-wide allelic DNA methylation map for both CG and non-CG sites in the mouse brain. We found parent-of-origin dependent (imprinted) ASM at 1,952 CGs which form 55 discrete clusters. This uncovers 31 reported differentially methylated regions (DMRs), including virtually all known germline DMRs, and 24 novel candidate DMRs with some occurring at microRNA genes. In the same adult tissue we also report a surprising presence of non-CG methylation with some showing evidence of imprinting. Finally, we identified sequence dependent ASM at 131,765 CGs. Interestingly, methylation at these sites exhibits a strong dependence on the immediate adjacent bases, allowing us to define a conserved sequence preference for the mammalian DNA methylation machinery. Our genome-wide ASM map should help with understanding the epigenetic differences between two parental genomes in mammals.
Project description:Allele specific DNA methylation (ASM) is crucial for genomic imprinting and mammalian development. Here we present a base-resolution, genome-wide allelic DNA methylation map for both CG and non-CG sites in the mouse brain. We found parent-of-origin dependent (imprinted) ASM at 1,952 CGs which form 55 discrete clusters. This uncovers 31 reported differentially methylated regions (DMRs), including virtually all known germline DMRs, and 24 novel candidate DMRs with some occurring at microRNA genes. In the same adult tissue we also report a surprising presence of non-CG methylation with some showing evidence of imprinting. Finally, we identified sequence dependent ASM at 131,765 CGs. Interestingly, methylation at these sites exhibits a strong dependence on the immediate adjacent bases, allowing us to define a conserved sequence preference for the mammalian DNA methylation machinery. Our genome-wide ASM map should help with understanding the epigenetic differences between two parental genomes in mammals.
Project description:Allele specific DNA methylation (ASM) is crucial for genomic imprinting and mammalian development. Here we present a base-resolution, genome-wide allelic DNA methylation map for both CG and non-CG sites in the mouse brain. We found parent-of-origin dependent (imprinted) ASM at 1,952 CGs which form 55 discrete clusters. This uncovers 31 reported differentially methylated regions (DMRs), including virtually all known germline DMRs, and 24 novel candidate DMRs with some occurring at microRNA genes. In the same adult tissue we also report a surprising presence of non-CG methylation with some showing evidence of imprinting. Finally, we identified sequence dependent ASM at 131,765 CGs. Interestingly, methylation at these sites exhibits a strong dependence on the immediate adjacent bases, allowing us to define a conserved sequence preference for the mammalian DNA methylation machinery. Our genome-wide ASM map should help with understanding the epigenetic differences between two parental genomes in mammals.
Project description:In vitro cortex generated from embryonic stem cells (ESCs) is a model system to investigate corticogenesis and a promising tool for cortical therapy. A fundamental question that has implications for understanding corticogenesis and for using stem cells therapeutically is to determine whether in vitro cortex reproduces some fine-tuned epigenetic modifications that are important for corticogenesis and function in vivo such as parent-of-origin dependent DNA methylation and expression of imprinted genes (IGs). Here, we have compared at single-base resolution the parent-of-origin dependent DNA methylation and expression of IGs in hybrid cortices generated either in vivo or in vitro from ESCs using Reduced Representation Bisulfite Sequencing (RRBS) and RNA-seq. We report that in vitro cortex strictly reproduced the in vivo parental expression of 41 IGs, including those involved in corticogenesis such as Mest (paternal) and Cdkn1c (maternal). The expressed allele was set in ESCs and maintained during in vitro corticogenesis for most IGs but some switched from a biallelic expression in ESCs to the monoallelic expression observed in vivo. RRBS experiments revealed that parent-of-origin dependent methylation at imprinted loci were also largely similar in in vitro and in vivo cortices except at a few loci. The most discordant locus was Gpr1-Zdbf2: Zdbf2 RNA was paternal in vivo and biallelic in vitro, and this was concomitant with an aberrant gain of methylation on the maternal allele in vitro. Thus, we conclude that the epigenetic mechanisms at imprinted loci are largely but not strictly preserved in vitro. We propose that in vitro corticogenesis, with its set of IGs displaying faithful parent-of-origin dependent expression and methylation, helps to define the poorly known mechanisms regulating imprinting in the brain and roles of IGs during corticogenesis.
Project description:Allele specific DNA methylation (ASM) is crucial for genomic imprinting and mammalian development. Here we present a base-resolution, genome-wide allelic DNA methylation map for both CG and non-CG sites in the mouse brain. We found parent-of-origin dependent (imprinted) ASM at 1,952 CGs which form 55 discrete clusters. This uncovers 31 reported differentially methylated regions (DMRs), including virtually all known germline DMRs, and 24 novel candidate DMRs with some occurring at microRNA genes. In the same adult tissue we also report a surprising presence of non-CG methylation with some showing evidence of imprinting. Finally, we identified sequence dependent ASM at 131,765 CGs. Interestingly, methylation at these sites exhibits a strong dependence on the immediate adjacent bases, allowing us to define a conserved sequence preference for the mammalian DNA methylation machinery. Our genome-wide ASM map should help with understanding the epigenetic differences between two parental genomes in mammals. The crosses of the two mouse strains 129x1/SvJ (129) and Cast/EiJ (Cast) were performed at Jackson Laboratories (http://jaxmice.jax.org/) and the male mice F1 offspring and males of each of the two parental strains were shipped to investigator laboratories at 8 to 9 weeks of age. A total of 500ng genomic DNA isolated from IMR90, MEF, and the frontal cortex of F1i and F1r was digested in parallel by the DNA methylation dependent restriction enzyme FspEI. FspEI recognizes the CmC site (the second cytosine is methylated and can be in the context of CG, CHG or CHH) and creates a 5 protruding end 17 bases downstream of the methylcytosine. A similar experiment was performed by incubating the F1i genomic DNA with a DNA methylation independent restriction enzyme BstNI. The digested DNA was gel purified, size selected for fragments within 100-600bp. The resulting DNA was then prepared as genomic DNA libraries for high-throughput sequencing (Illumina).