Project description:Allelic variation in gene expression is common in human genome. To understand genetic and epigenetic basis of allelic gene expression variation, we conducted allele specific RNA polymerase occupancy and allele specific gene expression analysis in CEPH lymphoblastoid cell lines.
Project description:We used microarrays to measure the expression levels of genes in irradiated immortalized B cells, lymphoblastoid cells, from members of Centre dEtude du Polymorphisme Humain (CEPH) Utah pedigrees. Data were collected for cells at baseline and 2 hour and 6 hour after exposure to 10 Gy of ionizing radiation (IR). Experiment Overall Design: We used microarrays to measure the expression levels of genes in irradiated immortalized B cells, lymphoblastoid cells, from members of 15 Centre dEtude du Polymorphisme Humain (CEPH) Utah pedigrees (CEPH 1333, 1341, 1346, 1362, 1408, 1416, 1420, 1421, 1423, 1424, 1444, 1447, 1451, 1454, 1582). Expression data was obtained for cell lines derived from 2 parents and 8 children per each family. Cells were irradiated at 10 Gy in a 137Cs irradiator. Cells were harvested prior to radiation and at 2 and 6 hours following exposure to IR.
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:Paired genomic DNA and cDNA samples obtained from lymphoblastoid cell lines from CEU and YRI HapMap individuals were hybridized to custom Illumina SNP arrays to study allele-specific expression in this tissue.
Project description:Histone modifications are important markers of function and chromatin state, yet the DNA elements that direct them to specific locations in the genome are poorly understood. Here we use the genetic variation in Yoruba lymphoblastoid cell lines as a natural experiment to identify genetic differences that affect histone marks and to better understand their relationship with transcriptional regulation. Across the genome, we identified hundreds of quantitative trait loci that impact histone modification or RNA polymerase (PolII) occupancy. In many cases the same variant is associated with quantitative changes in multiple histone marks and PolII, as well as in DNaseI sensitivity and nucleosome positioning, indicating that these molecular phenotypes often share a single underlying genetic cause. Variants that impact chromatin at distal regulatory sites frequently also direct changes in chromatin and gene expression at associated promoters; while most of these distal regulators enhance promoter activity, some act as distal chromatin silencers. Finally, we find that polymorphisms in transcription factor binding sites are often causally responsible for variation in local histone modification. In summary, the class of variants identified here generate coordinated changes in chromatin both locally and sometimes at distant locations, frequently drive changes in gene expression, and likely play an important role in the genetics of complex traits. ChIP-seq of RNA Polymerase II and 4 histone modifications (H3K4me1, H3K4me3, H3K27ac, H3K27me3) in 10 unrelated Yoruba HapMap lymphoblastoid cell lines
Project description:Baseline expression levels of genes in CEPH individuals from the International HapMap Project were measured using the Affymetrix Human Genome Focus Arrays. Arrays were analyzed using MAS 5.0 software (Affymetrix). Keywords = Gene Expression, lymphoblastoid cells, human Keywords: other
Project description:Understanding the genetic mechanisms underlying natural variation in gene expression is a central goal of both medical and evolutionary genetics, and studies of expression quantitative trait loci (eQTLs) have become an important tool for achieving this goal. While all eQTL studies to date have assayed mRNA levels using expression microarrays, recent advances in RNA sequencing enable the analysis of transcript variation at unprecedented resolution. We sequenced RNA from 69 lymphoblastoid cell lines (LCLs) derived from unrelated Nigerian individuals that have been extensively genotyped by the International HapMap Project. Pooling data from all individuals, we generated a map of the transcriptional landscape of these cells, identifying extensive use of unannotated polyadenylation sites and over 100 novel putative protein-coding exons. Using the genotypes from the HapMap project, we identified over a thousand genes at which genetic variation influences overall expression levels or splicing. We demonstrate that eQTLs near genes generally act via a mechanism involving allele-specific expression, and that variation that influences the inclusion of an exon is enriched within or near the consensus splice sites. Our results illustrate the power of high-throughput sequencing for the joint analysis of variation in transcription, splicing, and allele-specific expression across individuals. RNA-Seq in 69 lymphoblastoid cell lines from multiple Yoruban HapMap individuals in at least two replicate lanes per individual