Project description:<p>The common genetic variants associated with complex traits typically lie in non-coding DNA and may alter gene regulation in a cell type-specific manner. Consequently, the choice of tissue or cell model in the dissection of disease associations is important. We carried out an expression quantitative trait loci (eQTL) study of primary human osteoblasts (HOb) derived from 95 unrelated donors of Swedish origin, each represented by two independently derived primary lines to provide biological replication. We combined our data with publicly available information from a genome-wide association study (GWAS) of bone mineral density (BMD). The top 2000 BMD-associated SNPs were tested for cis-association of gene expression in HObs and in lymphoblastoid cell lines (LCLs) using publicly available data and showed that HObs have a significantly greater enrichment (threefold) of converging cis-eQTLs as compared to LCLs. The top 10 BMD loci with SNPs showing strong cis-effects on gene expression in HObs were selected for further validation using a staged design in two cohorts of Caucasian male subjects. All 10 variants were tested in the Swedish MrOS Cohort (n = 3014), providing evidence for two novel BMD loci (SRR and MSH3). These variants were then tested in the Rotterdam Study (n = 2090), yielding converging evidence for BMD association at the 17p13.3 SRR locus. The cis-regulatory effect was further fine-mapped to the proximal promoter of the SRR gene (rs3744270). Our results suggest that primary cells relevant to disease phenotypes complement traditional approaches for prioritization and validation of GWAS hits for follow-up studies.</p> <p>Reprinted from Grundberg E, Kwan T, Ge B et al., Genome Res Nov 2009, with permission from Genome Research, Cold Spring Harbor Press, PMID:<a href="http://www.ncbi.nlm.nih.gov/pubmed/19654370" target="_blank">19654370</a>.</p>
Project description:In this study, early infection by F. graminearum was characterized in a doubled-haploid population derived from the cross of the moderately FHB resistant wheat genotypes Wuhan 1 and Nyubai. Three significant QTL were identified: 1AL was associated with reduced deoxynivalenol levels, and 4BS and 5A were associated with reduced F. graminearum levels at 2 days after infection. The early resistance alleles for 1AL and 4BS were inherited from Wuhan 1, and those for the 5A QTL were inherited from Nyubai. The LOD support interval for the 5A QTL was in the same region as FHB5, a QTL previously associated with field resistance to FHB. Cis and trans eQTL were identified using RNA sequencing data from infected head samples. In total, 240 cis eQTL and 17,401 trans eQTL were identified within LOD support intervals for the three QTL. Hotspots for trans eQTL were identified within LOD support intervals for the 1AL and 4BS QTL. Differential gene expression analysis revealed twenty genes with cis eQTL within one of the 3 QTL support intervals, that had higher expression associated with FHB early resistance, and 17 genes with higher expression associated with FHB early susceptibility. Among those, genes with a cis eQTL peak coinciding with QTL peaks were enriched in functions related to signaling and protein-protein interaction, including NBS-LRR, BAH, LRR/F-box and TPR domain-containing proteins. Several genes located within one of the three QTL support intervals also had a trans eQTL with a peak at the same position as QTL peaks on other chromosomes, suggesting interactions between the QTL.
Project description:We used microarrays and a previously established linkage map to localize the genetic determinants of brain gene expression for a backcross family of lake whitefish species pairs (Coregonus sp.). Our goals were to elucidate the genomic distribution and sex-specificity of brain expression QTL (eQTL) and to determine the extent to which genes controlling transcriptional variation may underlie adaptive divergence in the recently evolved dwarf (limnetic) and normal (benthic) whitefish. We observed a sex-bias in transcriptional genetic architecture, with more eQTL observed in males, as well as divergence in genome location of eQTL between sexes. Hotspots of nonrandom aggregations of up to 32 eQTL in one location were observed. We identified candidate genes for species pair divergence involved with energetic metabolism, protein synthesis, and neural development based on co-localization of eQTL for these genes with eight previously identified adaptive phenotypic QTL and four previously identified outlier loci from a genome scan in natural populations. 88% of eQTL-phenotypic QTL co-localization involved growth rate and condition factor QTL, two traits central to adaptive divergence between whitefish species pairs. Hotspots co-localized with phenotypic QTL in several cases, revealing possible locations where master regulatory genes, such as a zinc finger protein in one case, control gene expression directly related to adaptive phenotypic divergence. We observed little evidence of co-localization of brain eQTL with behavioral QTL, which provides insight on the genes identified by behavioral QTL studies. These results extend to the transcriptome level previous work illustrating that selection has shaped recent parallel divergence between dwarf and normal lake whitefish species pairs and that metabolic, more than morphological differences appear to play a key role in this divergence. Keywords: eQTL mapping, gene expression, linkage mapping, adaptive radiation, Coregonus, microarrays
Project description:We used microarrays and a previously established linkage map to localize the genetic determinants of brain gene expression for a backcross family of lake whitefish species pairs (Coregonus sp.). Our goals were to elucidate the genomic distribution and sex-specificity of brain expression QTL (eQTL) and to determine the extent to which genes controlling transcriptional variation may underlie adaptive divergence in the recently evolved dwarf (limnetic) and normal (benthic) whitefish. We observed a sex-bias in transcriptional genetic architecture, with more eQTL observed in males, as well as divergence in genome location of eQTL between sexes. Hotspots of nonrandom aggregations of up to 32 eQTL in one location were observed. We identified candidate genes for species pair divergence involved with energetic metabolism, protein synthesis, and neural development based on co-localization of eQTL for these genes with eight previously identified adaptive phenotypic QTL and four previously identified outlier loci from a genome scan in natural populations. 88% of eQTL-phenotypic QTL co-localization involved growth rate and condition factor QTL, two traits central to adaptive divergence between whitefish species pairs. Hotspots co-localized with phenotypic QTL in several cases, revealing possible locations where master regulatory genes, such as a zinc finger protein in one case, control gene expression directly related to adaptive phenotypic divergence. We observed little evidence of co-localization of brain eQTL with behavioral QTL, which provides insight on the genes identified by behavioral QTL studies. These results extend to the transcriptome level previous work illustrating that selection has shaped recent parallel divergence between dwarf and normal lake whitefish species pairs and that metabolic, more than morphological differences appear to play a key role in this divergence. Keywords: eQTL mapping, gene expression, linkage mapping, adaptive radiation, Coregonus, microarrays The objective of this study was to elucidate the genomic distribution and sex-specificity of brain eQTL in dwarf and normal lake whitefish. Dissected brain tissue (250-350 mg) was sampled for 55 individuals from a hybrid x dwarf backcross mapping family. We used a loop design (YANG and SPEED 2002; CHURCHILL 2002) to maximize the number of sampled meioses. Each of 55 samples was technically replicated on two distinct slides, while performing dye swapping (Cy3 and Alexa) to estimate the dye intensity variation bias. After correcting for local background, raw intensity values were both log2 transformed and normalized using the regional LOWESS method implemented in the R/MANOVA software (KERR et al. 2000). We used a previously generated linkage map based on the same backcross individuals for which gene expression was measured. eQTL mapping was performed with QTL Cartographer.
Project description:Anterior pituitary glands were isolated from 21 week old male rats treated for 12 weeks with the synthetic estrogen diethylstilbestrol (DES). 43 COPxACI F2 animals were selected based on pituitary weight phenotypic extremes: 22 highest and 21 lowest pituitary weights in our F2 population. Expression profiles were determined using Affymetrix Rat Genome 230 v. 2.0 arrays. In conjunction with genomewide genotypes available for these 43 animals, linkage analysis was done using mRNA abundance of each transcript on the array as a separate quantitative phenotype. These arrays provide a resource for expression QTL (eQTL) mapping on a genomewide level in the pituitary gland. Keywords: Estrogen Response
Project description:gnp07_rilkit - rilkit-eqtl analysis (random pair design). To provide quantitative geneticists studying natural variation in our RIL populations with information and resources necessary to speed up QTL cloning and candidate genes identification. This articulates around the creation of two major resources and their integration into databases to make the information accessible to users: A. Whole transcriptome survey, B. Production of complementary material. Comparison of 164 Cvi/Col(8RV) Recombinant Inbred Lines (RILs) and 164 Bur/Col (20RV) RILs.
Project description:To explore the roles of cell-type specific methylation QTL (meQTL) for melanoma GWAS annotation, we generated DNA methylation data from the same sample set as our previouse eQTL study including 106 primary melanocyte cultures. The Illumina Infinium 450k Human DNA methylation Beadchip v1.2 was used to obtain DNA methylation profiles across approximately 480,000 CpGs in 106 primary melanocyte cultures. To be able to identify the DNA methylation probes whose methylation levels are correlated with germline genetic variants including the ones associated with melanoma, meQTL analysis was performed in these 106 primary melanocyte cultures using the same method as we did for eQTL study.
Project description:gnp07_rilkit - rilkit-eqtl analysis (random pair design). To provide quantitative geneticists studying natural variation in our RIL populations with information and resources necessary to speed up QTL cloning and candidate genes identification. This articulates around the creation of two major resources and their integration into databases to make the information accessible to users: A. Whole transcriptome survey, B. Production of complementary material. Comparison of 164 Cvi/Col(8RV) Recombinant Inbred Lines (RILs) and 164 Bur/Col (20RV) RILs. 162 dye-swaps. Genotype and ecotype comparison.