Hybrid mice reveal parent-of-origin and cis- and trans-regulatory effects in the retina
ABSTRACT: A fundamental challenge in genomics is to map DNA sequence variants onto changes in gene expression. Gene expression is regulated by cis-regulatory elements (CREs, i.e., enhancers, promoters, and silencers) and the trans factors (e.g., transcription factors) that act upon them. A powerful approach to dissecting cis and trans effects is to compare F1 hybrids with F0 homozygotes. Using this approach and taking advantage of the high frequency of polymorphisms in wild-derived inbred Cast/EiJ mice relative to the reference strain C57BL/6J, we conducted allele-specific mRNA-seq analysis in the adult mouse retina, a disease-relevant neural tissue. We found that cis effects account for the bulk of gene regulatory divergence in the retina. Many CREs contained functional (i.e., activating or silencing) cis-regulatory variants mapping onto altered expression of genes, including genes associated with retinal disease. By comparing our retinal data with previously published liver data, we found that most of the cis effects identified were tissue-specific. Lastly, by comparing reciprocal F1 hybrids, we identified evidence of imprinting in the retina for the first time. Our study provides a framework and resource for mapping cis-regulatory variants onto changes in gene expression, and underscores the importance of studying cis-regulatory variants in the context of retinal disease. Retinas from four classes of 8 week old male mice were collected: F0 C57BL/6J (B6), F0 Cast/EiJ (Cast), F1 B6xCast, and F1 CastxB6. Three replicates per class were generated. Each replicate consisted of a pool of 6-8 retinas. The mRNA-seq was conducted with paired-end 2x101 sequencing on the Illumina HiSeq 2000 platform. One lane of sequencing was run for all twelve samples. An additional lane of sequencing was run for the six F1 samples.
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:Endoplasmic reticulum (ER) stress occurs when misfolded proteins accumulate in the ER. The cellular response to ER stress involves complex transcriptional and translational changes, important to the survival of the cell. ER stress is a primary cause and a modifier of many human diseases. A first step to understanding how the ER stress response impacts human disease is to determine how the transcriptional response to ER stress varies among individuals. The genetic diversity of the eight mouse Collaborative Cross (CC) founder strains allowed us to determine how genetic variation impacts the ER stress transcriptional response. We used tunicamycin, a drug commonly used to induce ER stress, to elicit an ER stress response in mouse embryonic fibroblasts (MEFs) derived from the CC founder strains and measured their transcriptional responses. We identified hundreds of genes that differed in response to ER stress across these genetically diverse strains. Strikingly, inflammatory response genes differed most between strains; major canonical ER stress response genes showed relatively invariant responses across strains. To uncover the genetic architecture underlying these strain differences in ER stress response, we measured the transcriptional response to ER stress in MEFs derived from a subset of F1 crosses between the CC founder strains. We found a unique layer of regulatory variation that is only detectable under ER stress conditions. Over 80% of the regulatory variation under ER stress derives from cis-regulatory differences. This is the first study to characterize the genetic variation in ER stress transcriptional response in the laboratory mouse. Our findings indicate that the ER stress transcriptional response is highly variable among strains and arises from genetic variation in individual downstream response genes, rather than major signaling transcription factors. These results have important implications for understanding how genetic variation impacts the ER stress response, an important component of many human diseases. We investigated the genetic variation in ER stress transcriptional response in mouse embryonic fibroblasts (MEFs) across eight mouse strains: A/J, C57BL/6J, 129S1Sv/ImJ, NOD/ShiLtJ, NZO/H1LtJ, CAST/EiJ, PWK/PhJ, and WSB/EiJ. MEFs from each strain were treated with a control DMSO or ER stress-inducing drug, Tunicamycin (TM). To identify the genetic architecture underlying this genetic variation, MEFs from F1 strains were also studied. MEFs from the following F1s were evaluated: C57BL/6J X CAST/EiJ, C57BL/6J X 129S1Sv/ImJ, C57BL/6J X NOD/ShiLtJ, C57BL/6J X NZO/H1LtJ, and C57BL/6J X WSB/EiJ. Again F1 MEFS were treated with either DMSO or TM. There are two or three replicates for each sample.
Project description:Genetically distinct individuals are differentially affected by the DNA damaging effects of exposure to environmental toxicants, but the mechanisms contributing to these differences are poorly understood. It is known that genetic variation affects the establishment of the gene regulatory landscape, and we hypothesized that this may significantly contribute to the observed heterogeneity in individual responses to exogenous cellular insults. In this study, we investigated how genetic variation and chromatin organization may dictate susceptibility to DNA damage. We measured DNA damage, mRNA and miRNA expression, and chromatin accessibility genome-wide in lung tissue from two genetically-divergent inbred mouse strains, C57BL/6J and CAST/EiJ, at baseline and in response to exposure to a model DNA-damaging chemical, 1,3-butadiene (BD). Our results show that unexposed CAST/EiJ and unexposed C57BL/6J mice have very different chromatin organization and transcription profiles in the lung. Importantly, in unexposed CAST/EiJ, which is more resistant to BD-induced DNA damage, we see increased transcription and a more accessible chromatin landscape around genes involved in detoxification pathways. Upon BD exposure, chromatin is significantly remodeled in C57BL/6J around these genes to more closely resemble that found in CAST/EiJ. This suggests that strain-specific differences in baseline chromatin organization and transcription contribute to the relative resistance of CAST/EiJ to the DNA damaging effects of BD. Based on these results, we propose more generally that differences in the baseline molecular state of key tissues, driven by unique genetic backgrounds, significantly contributes to inter-individual variability in response to DNA-damaging environmental agents. Overall design: Investigation of strain-specific chromatin accessibility and gene expression differences in lung tissue from CAST/EiJ and C57BL/6J mice, and how the gene regulatory landscape changes in response to 1,3-Butadiene exposure
Project description:We report testis H3K4me3 enrichment in an F1 male from a C57BL/6J (B6) x CAST/Eij (CAST) cross (B6 mother, CAST father). This mouse is heterozygous at PRDM9 for a humanized allele (Davies et al. Nature 2016) and the CAST allele. After filtering of promoter H3K4me3 regions, these data serve as a measure of PRDM9 binding enrichment on each homologue. We found that both crossovers and non-crossovers (observed by sequencing F2 genomic DNA) are depleted at "asymmetric" Double-Strand Break hotspots where PRDM9 primarily binds only one of the two homologues. This proves that PRDM9 plays an important role in promoting inter-homologue interactions and can explain why increasing PRDM9 binding asymmetry predicts hybrid infertility. See Li, Bitoun, Altemose et al. 2018 (pending) for a complete summary. Overall design: Two replicates of anti-H3K4me3 ChIP-seq, one per testis, plus an input chromatin control, from a male B6CAST-F1-PRDM9 Humanized/CAST mouse
Project description:We have identified candidate genes from the Feml2 QTL influencing femur length through allele specific expression analysis of growth plates in C57BL/6J x CAST/EiJ F1 hybrids. This work provides the foundation to identify novel genes affecting bone geometry. Overall design: total RNA sequencing in 7 male C57BL/6JxCAST F1s
Project description:RNA-Seq was performed on mESCs generated from F1 hybrids from reciprocal crosses of C57BL/6J and CAST/EiJ, denoted B and C hereafter; cell lines are designated as BC or CB, with the maternal line symbolized first Overall design: 3 XX and 3 XY lines were used from each cross as well as two XO lines for a total of 14 samples.
Project description:We profiled the genome-wide occupancy of three tissue-specific transcription factors, HNF4A, CEBPA and FOXA1, as well as the genome-wide occurrence of the histone mark, H3K4me3 in the livers of two inbred parental mouse strains (C57BL/6J and CAST/EiJ) and their F1 crosses. We also included H3K27ac data generated from F1 hybrids as well as the profiling of HNF4A, CEBPA and FOXA1 in both CEBPA and HNF4a heterozygous knock-outs.
Project description:The inactive X chromosome’s (Xi) physical territory is microscopically devoid of transcriptional hallmarks and enriched in silencing-associated modifications. How these microscopic signatures relate to specific Xi sequence is unknown. This study reports the profiling of Xi gene expression and chromatin states at high-resolution via allele-specific sequencing in F1 hybrid mouse trophoblast stem cells (TSCs). Datasets provided include those generated from strand-specific RNA-Seq, ChIP-Seq, FAIRE-Seq, and DNase-Seq protocols. Included for each dataset are FASTQ files, BED alignments and WIG files with coordinates relative to UCSC genome build mm9, and _snp files that report the location of all SNP-overlapping reads. The F1 TSC lines profiled were generated from crosses between CAST/EiJ (Cast) and C57BL/6J (B6) mice. C/B denotes a Cast mother and B6 father, and B/C denotes a B6 mother and Cast father.
Project description:We profiled genome-wide gene expression of 170 individual mid-gestation (embryonic day 11.5) whole mouse embryos derived from a 2-generation interspecies mouse cross and asked to what extent genetic variation drives four important parameters of regulatory architecture: allele-specific expression (ASE), imprinting, trans-regulatory effects, and maternal effect. The inbred strain C57BL/6J and wild-derived inbred strain CAST/EiJ were used in reciprocal crosses to generate F1 embryos. F1 progeny were backcrossed to C57BL/6J in reciprocal crosses to generate 154 N2 embryos. We employed a backcross design, in which N2 offspring have genotypically distinct parents, to enable comparison of gene expression for offspring from each side of the reciprocal cross. Our findings demonstrate that genetic variation contributes to widespread gene expression differences during mammalian embryogenesis. Transcriptome analysis of E11.5 mouse embryos: 16 F1 embryos from reciprocally crossed C57BL/6J and CastEi/J parents; and 154 N2 embryos from reciprocal backcross of F1s to the C57BL/6J parent.
Project description:Adult female Wistar rats (about 220g) obtained from a breeding colony were mated and fed either a protein sufficient (PS) or protein restricted (PR) diet (n = 6 per dietary group) during F0 pregnancy which provided an increase in energy of approximately 25% compared to the diet fed to the breeding colony (2018S). During lactation dams were fed AIN93G and litters were standardisied to 8 offspring within 24 hours of birth with a bias towards females. Offpsring were weaned onto AIN93M at postnatal day 28 and F1 and F2 females were mated on postnatal day 70 (n = 6 per F0 dietary group). F1 and F2 dams were fed the PS diet during pregnancy and AIN93G during lactation. Offspring were weaned onto AIN93M. On postnatal day 70 unmated female offspring were fasted for 12 hours then sacrificed for hepatic transcritpome analysis by microarray. Expression of 1,684 genes differed by at least 2 fold between adult female F1 offspring of F0 dams from both dietary groups. 1680 genes were altered in F2 offspring and 2,065 genes altered in F3 offspring. Expression of 113 genes was altered in all three generations. Of these, 47% showed directionally opposite differences between generations. Gene ontology analysis revealed clear differences in the pathways altered in each generation. F1 and F2 offspring of F0 dams fed a PR diet showed impaired fasting glucose homeostasis. Hepatic phosphoenolpyruvate carboxykinase (PEPCK) expression was elevated in F1 and F2 offspring from F0 PR dams, but decreased in F3, compared to PS offspring