Quantitative analysis of chromatin interactions upon copy number variation at mouse 4E2 [RNA-seq]
ABSTRACT: The three-dimensional organization of chromatin has a critical impact on the regulation of gene expression. However, little is known about the effect of DNA copy number variants (CNVs) on chromatin organization. We performed an allele-specific chromatin conformation and gene expression analysis of wild-type (WT) mouse chromosome 4 and an engineered 4.3Mb chromosome 4 deletion in mouse embryonic fibroblasts. A newly developed quantitative framework for the analysis of paired-end 4C-seq data revealed a number of significant differentially interacting regions (DIRs) and higher-order chromatin compaction changes present in the deletion chromosome. Selected DIRs were validated by 3D DNA FISH experiments. We discovered a significant enrichment of CTCF and Smc1 binding sites within DIRs, as well as differentially expressed genes determined by RNA-Seq. Together, our findings highlight the complex effects of a 4E2 CNV on chromatin structure and function, both locally in the deletion chromosome and globally in the WT copy. Examination of chromatin contacts and gene expression in wild type chromosome 4 and a 4.3Mb deletion in chromosome 4 in mouse
Project description:X chromosome inactivation (XCI) silences most genes on one X chromosome in female mammals, but some genes escape XCI. To identify escape gene in vivo and to explore molecular mechanisms that regulate this process we analyzed the allele-specific expression and chromatin structure of X-linked genes in mouse tissues and cells with skewed XCI and distinguishable alleles based on single nucleotide polymorphisms. Using a new method to estimate allelic expression, we demonstrate a continuum between complete silencing and significant expression from the inactive X (Xi). Few genes (2-3%) escape XCI to a significant level and only a minority differs between mouse tissues, suggesting stringent silencing and escape controls. Allelic profiles of DNase I hypersensitivity and RNA polymerase II occupancy of genes on the Xi correlate with escape from XCI. Allelic binding profiles of the DNA binding protein CCCTC-binding factor (CTCF) in different cell types indicate that CTCF binding at the promoter correlates with escape. Importantly, CTCF binding at the boundary between escape and silenced domains may prevent the spreading of active escape chromatin into silenced domains. Examination of allelic expression in mouse hybrid tissues.
Project description:X chromosome inactivation (XCI) silences most genes on one X chromosome in female mammals, but some genes escape XCI. To identify escape gene in vivo and to explore molecular mechanisms that regulate this process we analyzed the allele-specific expression and chromatin structure of X-linked genes in mouse tissues and cells with skewed XCI and distinguishable alleles based on single nucleotide polymorphisms. Using a new method to estimate allelic expression, we demonstrate a continuum between complete silencing and significant expression from the inactive X (Xi). Few genes (2-3%) escape XCI to a significant level and only a minority differs between mouse tissues, suggesting stringent silencing and escape controls. Allelic profiles of DNase I hypersensitivity and RNA polymerase II occupancy of genes on the Xi correlate with escape from XCI. Allelic binding profiles of the DNA binding protein CCCTC-binding factor (CTCF) in different cell types indicate that CTCF binding at the promoter correlates with escape. Importantly, CTCF binding at the boundary between escape and silenced domains may prevent the spreading of active escape chromatin into silenced domains. Examination of CTCF and RNA PolIIS5p occupancy in mouse hybrid cells and adult tissues.
Project description:In mammals, genes located on the X chromosome are present in one copy in XY males and two in XX females. To balance the dosage of X-linked gene expression between the sexes one of the two X chromosomes in females is silenced by X inactivation initiated by up-regulation of the lncRNA (long non-coding RNA) Xist and recruitment of specific chromatin modifiers for silencing. The inactivated X chromosome becomes heterochromatic and visits a specific nuclear compartment adjacent to the nucleolus. We report a novel role for the X-linked lncRNA Firre in anchoring the inactive mouse X chromosome and preserving one of its main epigenetic features, trimethylation of histone H3 at lysine 27 (H3K27me3). Similar to Dxz4, Firre is expressed from a macrosatellite repeat locus associated with a cluster of CTCF and cohesin binding specifically on the inactive X. CTCF binding initially present in both male and female mouse embryonic stem cells was found to be lost from the active X during development. The Firre and Dxz4 loci on the inactive X were preferentially located adjacent to the nucleolus. Knockdown of Firre RNA disrupted perinucleolar targeting and H3K27me3 levels in mouse fibroblasts, demonstrating an important role for this lncRNA in maintenance of one of the main epigenetic features of the X chromosome. There was no X-linked gene reactivation after Firre knockdown; however, a compensatory increase in the expression of chromatin modifier genes implicated in X silencing was observed. In female ES cells Firre RNA knockdown did not disrupt Xist expression/coating nor silencing of G6pdx during differentiation, suggesting that Firre does not play a role in the onset of X inactivation. We conclude that the X-linked lncRNA Firre helps position the inactive X chromosome near the nucleolus and preserve one of its main epigenetic features. Examination of allelic expression in Patski cells upon Firre knockdown.
Project description:We report the application of single-molecule-based sequencing technology for high-throughput profiling of RNA polymerase II phosphorylated at serine 5 (PolII-S5p; the transcription initiation form) in female mouse cultured hybrid cells and female hybrid brain derived from mouse systems with skewed X inactivation based on crosses between C57BL/6J (BL6) and M. spretus. In these systems, alleles can be differentiated by frequent SNPs between mouse species, and the active X (Xa) compared to the haploid set of autosomes from the same species. To examine PolII-S5p occupancy in vivo, ChIP-seq was done in brain from an adult female F1 mouse in which the BL6 X is always active and the spretus X inactive. Uniquely mapped reads containing informative SNPs were assigned to each haploid chromosome set (BL6 or spretus) and were counted to establish allele-specific PolII-S5p occupancy profiles. We found that PolII-S5p allele-specific occupancy with or without normalization by input genomic DNA sequencing data showed that expressed genes on the Xa (>1RPKM) had 30% higher PolII-S5p peak levels at their promoters compared to autosomal genes from the same species (BL6). This result was confirmed by performing an independent allele-specific ChIP-seq analysis on fibroblasts derived from embryonic kidney (Patski cell line) that have the opposite X inactivation pattern from the brain sample, i.e. an Xa from M. spretus and an Xi from BL6. These findings suggest that transcription initiation of X-linked genes is enhanced to contribute to X upregulation in cell lines and in vivo. Examination of allele-specific PolII-S5p occupancy in mouse hybrid cells and brain.
Project description:We report genomic imprinting effects in the arcuate nucleus, dorsal raphe nucleus, liver and muscle of adult female mice Examination of allele-specific gene expression hybrid mice generated from reciprocal crosses of CastEiJ x C57BL/6J mice
Project description:The maternal and paternal genomes play different roles in mammalian brains as a result of genomic imprinting, an epigenetic regulation leading to differential expression of the parental alleles of some genes. Here we investigate genomic imprinting in the cerebellum using a newly developed Bayesian statistical model that provides unprecedented transcript-level resolution. We uncover 160 imprinted transcripts, including 41 novel and independently validated imprinted genes. Strikingly, many genes exhibit parentally biased -rather than monoallelic- expression, with different magnitudes according to age, organ, and brain region. Developmental changes in parental bias and overall gene expression are strongly correlated, suggesting combined roles in regulating gene dosage. These findings reveal the remarkable complexity of genomic imprinting, with important implications for understanding the normal and diseased brain. 48 samples of F1 mouse hybrids produced by crossing C57Bl/6J males with Cast/EiJ females (denoted as F1i) and reciprocally crossing Cast/EiJ males and C57Bl/6J famales (denoted as F1r).
Project description:Two inbred mouse strains, C57BL/6J and CAST/EiJ, were crossed to generate both initial and reciprocal F1 crosses. For each genetically distinct class of mice (F0 C57BL/6J, F0 CAST/EiJ, F1i - C57BL/6J x CAST/EiJ, F1r - CAST/EiJ x C57BL/6J, where the male parent is listed first), samples were collected from a single lobe of the liver from 6 male mice between the ages of 4 and 6 months. The 24 samples were then processed to generate strand-specific RNA-seq libraries, which were sequenced on the Illumina GAII platform using 72bp paired-end reads.
Project description:The host response to influenza A infections is strongly influenced by host genetic factors. Animal models of genetically diverse mouse strains are well suitable to identify host genes involved in severe pathology, viral replication and immune responses. Here, we have utilizing a dual RNAseq approach that allowed us to investigate both viral and host gene expression in the same individual from a single expression assay after H1N1 infection. We performed a comparative expression analysis to identify (i) correlations between host genes and the viral gene expression, (ii) host genes involved in viral replication, and (iii) genes showing differential expression between the two mouse strains after infection. These genes may be key players involved in regulating the differences in pathogenesis and host defense mechanisms after influenza A infections. Expression levels of influenza segments correlated well with the viral load and may thus be used as surrogates for conventional viral load measurements. Furthermore, we investigated the functional role of two genes, Reg3g and Irf7, in knock-out mice and found that deletion of the Irf7 gene renders the host highly susceptible to H1N1 infection. Female, 10-12 weeks old mice were anesthetized by intra-peritoneal injection with Ketamine/Xylazine (85% NaCl (0.9%), 10% Ketamine, 5% Xylazine) with doses adjusted to the individual body weight. Mice were then intra-nasally infected with 20µl virus solution (2x10³ FFU PR8M) or mock-treated with PBS.
Project description:The recent development of next-generation sequencing (NGS) techniques encouraged us to assess the transcriptome of the murine OE. We analyzed RNA from OEs of female and male adult mice and from fluorescence-activated cell sorting (FACS)-sorted olfactory receptor neurons (ORNs) obtained from transgenic OMP-GFP mice The Illumina RNA-Seq protocol was utilized to generate up to 86 million reads per transcriptome.
Project description:Genomic imprinting results in the preferential expression of the paternal, or maternal allele of certain genes. We have performed a genome-wide characterization of imprinting in the mouse embryonic and adult brain using F1 hybrid mice generated from reciprocal crosses of CASTEiJ and C57BL/6J mice. We also uncovered genes associated with sex specific parental effects in the adult mouse brain. Our study identified preferential selection of the maternally inherited X chromosome in glutamatergic neurons of the female cortex. Examination of allele specific expression in the brains of reciprocal crosses of F1 hybrid mice from CASTEiJ and C57BL/6J crosses. Processed data files (GenomicAligned, SNP_calls, TranscriptomeAligned, fRNAdbAligned) and README file linked below as supplementary files.