Project description:It is well established that epigenetic features, such as histone modifications and DNA methylation, are associated with gene expression across cell types. However, it is not well known how variation in genotype affects epigenetic state, or to what extent such variation contributes to variation in gene expression across genetically distinct individuals. Here we investigated the relationship between heritable epigenetic variation and gene expression in hepatocytes across nine inbred mouse strains. Eight of the inbred strains were founders of the diversity outbred (DO) mice, and the ninth was DBA/2J, which, along with C57BL/6J, is one of the founders of the BxD recombinant inbred panel of mice. We surveyed four histone modifications, H3K4me1, H3K4me3, H3K27me3 and H3K27ac, as well as DNA methylation. We used ChromHMM to identify 14 chromatin states representing distinct combinations of the four measured histone modifications. We found that variation in chromatin state mirrored genetic variation across the inbred strains. Furthermore, epigenetic variation was correlated with gene expression across strains. The correspondence between epigenetic state and gene expression was replicated in an independent population of DO mice in which we imputed local epigenetic state. In contrast, we found that DNA methylation did not vary across inbred strains and was not correlated with variation in expression in DO mice. This work suggests that chromatin state is highly influenced by local genotype and may be a primary mode through which expression quantitative trait loci (eQTLs) are mediated. We further demonstrate that strain variation in chromatin state, paired with gene expression is useful for annotation of functional regions of the mouse genome. Finally, we provide a data resource that documents variation in chromatin state across genetically distinct individuals.
Project description:Natural variation in protein expression is common in all organisms and contribute to phenotypic differences among individuals. While variation in gene expression at the transcript level has been extensively investigated, the genetic mechanisms underlying variation in protein expression have lagged considerably behind. Here we investigate genetic architecture of protein expression by profiling a deep mouse brain proteome of two inbred strains, C57BL/6J (B6) and DBA/2J (D2), and their reciprocal F1 hybrids using two-dimensional liquid chromatography coupled with tandem mass spectrometry (LC/LC-MS/MS) technology. By comparing protein expression levels in the four mouse strains, we observed 329 statistically significant differentially expressed proteins between the two parental strains and identified four common inheritance patterns, including dominant, additive, over- and under-dominant expression. We further applied the proteogenomic approach to detect variant peptides and define protein allele-specific expression (pASE).
Project description:It is well established that epigenetic features, such as histone modifications and DNA methylation, are associated with gene expression across cell types. However, it is not well known how variation in genotype affects epigenetic state, or to what extent such variation contributes to variation in gene expression across genetically distinct individuals. Here we investigated the relationship between heritable epigenetic variation and gene expression in hepatocytes across nine inbred mouse strains. Eight of the inbred strains were founders of the diversity outbred (DO) mice, and the ninth was DBA/2J, which, along with C57BL/6J, is one of the founders of the BxD recombinant inbred panel of mice. We surveyed four histone modifications, H3K4me1, H3K4me3, H3K27me3 and H3K27ac, as well as DNA methylation. We used ChromHMM to identify 14 chromatin states representing distinct combinations of the four measured histone modifications. We found that variation in chromatin state mirrored genetic variation across the inbred strains. Furthermore, epigenetic variation was correlated with gene expression across strains. The correspondence between epigenetic state and gene expression was replicated in an independent population of DO mice in which we imputed local epigenetic state. In contrast, we found that DNA methylation did not vary across inbred strains and was not correlated with variation in expression in DO mice. This work suggests that chromatin state is highly influenced by local genotype and may be a primary mode through which expression quantitative trait loci (eQTLs) are mediated. We further demonstrate that strain variation in chromatin state, paired with gene expression is useful for annotation of functional regions of the mouse genome. Finally, we provide a data resource that documents variation in chromatin state across genetically distinct individuals.
Project description:It is well established that epigenetic features, such as histone modifications and DNA methylation, are associated with gene expression across cell types. However, it is not well known how variation in genotype affects epigenetic state, or to what extent such variation contributes to variation in gene expression across genetically distinct individuals. Here we investigated the relationship between heritable epigenetic variation and gene expression in hepatocytes across nine inbred mouse strains. Eight of the inbred strains were founders of the diversity outbred (DO) mice, and the ninth was DBA/2J, which, along with C57BL/6J, is one of the founders of the BxD recombinant inbred panel of mice. We surveyed four histone modifications, H3K4me1, H3K4me3, H3K27me3 and H3K27ac, as well as DNA methylation. We used ChromHMM to identify 14 chromatin states representing distinct combinations of the four measured histone modifications. We found that variation in chromatin state mirrored genetic variation across the inbred strains. Furthermore, epigenetic variation was correlated with gene expression across strains. The correspondence between epigenetic state and gene expression was replicated in an independent population of DO mice in which we imputed local epigenetic state. In contrast, we found that DNA methylation did not vary across inbred strains and was not correlated with variation in expression in DO mice. This work suggests that chromatin state is highly influenced by local genotype and may be a primary mode through which expression quantitative trait loci (eQTLs) are mediated. We further demonstrate that strain variation in chromatin state, paired with gene expression is useful for annotation of functional regions of the mouse genome. Finally, we provide a data resource that documents variation in chromatin state across genetically distinct individuals.
Project description:The Mouse Genomes Project ( http://www.sanger.ac.uk/science/data/mouse-genomes-project ) uses using next-generation sequencing technologies to catalogue molecular variation in the common laboratory mouse strains, and a selected set of wild-derived inbred strains. Access to complete sequence of multiple inbred strains will add to these resources and will become a permanent foundation for a systems biology approach to phenotypic variation in the mouse. In this particular study, we have sequenced the transcriptome of whole-brain tissue from 16 laboratory mouse strains to examine differences in gene expression levels, differential RNA-editing, and for use in de novo gene prediction.
Project description:We have conducted a genome-wide analysis of spontaneous copy number variation (CNV) in the laboratory mouse. We used high resolution microarrays to identify 38 CNVs between 14 colonies of the C57BL/6 strain spanning ~967 generations of inbreeding, and examined these loci in 12 additional strains. It is clear from our results that many CNVs arise through a highly non-random process: 18 of 38 were the product of recurrent mutation, and rates of change vary roughly four orders of magnitude across different loci. These recurrent CNVs are distributed throughout the genome, affect 43 genes, and fluctuate in copy number over mere hundreds of generations, observations that raise questions about their contribution to natural variation. Keywords: Representational oligonucleotide microarray analysis, comparative genomic hybridization, DNA copy number variation, structural variation, inbred mice, spontaneous mutation rate