Project description:Noncoding variants play a central role in the genetics of complex traits, but we still lack a full description of the main molecular pathways through which they act. Here we used molecular data to quantify the contribution of cis-acting genetic effects at each major stage of gene regulation from chromatin to proteins, within a population sample of Yoruba lymphoblastoid cell lines (LCLs). We performed 4sU metabolic labeled transcripts in 65 YRI LCLs to identify genetic variants that affect transcription rates. As expected, we found an important contribution of genetic variation via chromatin, contributing â¼65% of eQTLs (expression Quantitative Trait Loci). The remaining eQTLs, which are not asso- ciated with chromatin-level variation, are highly enriched in transcribed regions, and hence may affect expression through co- or post-transcriptional processes. International HapMap lymphoblastoid cell lines (LCLs) derived from YRI (Yoruba in Ibadan, Nigeria); We adapted the 4sU labelling method from (PMID 21516085). Briefly, cell cultures were grown to log phase in volumes sufficient to yield about 300 ng of 4sU-labeled RNA. Cells were incubated with 4sU for the required length of time (0, 30, or 60 minutes), then washed, pelleted, and frozen. Total RNA was extracted, and 4sU-labeled RNA was separated from total RNA using a bead-based biotin-streptavidin purification protocol. We sequenced metabolic labeled transcripts in 65 YRI LCLs 30 minutes and 60 minutes after incubation.
Project description:Ethnic differences in human DNA methylation have been shown for a number of CpG sites, but the genome-wide patterns and extent of these differences are unknown. In addition, whether the genetic control of polymorphic DNA methylation is population-specific has not been investigated. Here we measure DNA methylation near the transcription start sites of over 14,000 genes in 180 cell lines derived from one African and one European population. We find population-specific patterns of DNA methylation at over a third of all genes. Furthermore, although the methylation at over a thousand CpG sites is heritable, these heritabilities are also distinctly different between populations, suggesting extensive divergence in the genetic control of DNA methylation. In support of this, genetic mapping of DNA methylation reveals that there is also little overlap in genetic associations between populations. This population-specificity is supported by the patterns of DNA methylation in several hundred brain samples, suggesting it holds in vivo and across tissues. These results suggest that DNA methylation is highly divergent between populations, and that this divergence may be due in large part to complex epistasis or gene x environment interactions. Genomic DNA from 180 lymphoblastoid cell lines were bisulphite converted and hybridized, along with 8 additional technical replicates, to the Illumina Infinium HumanMethylation27 Beadchip v1.2 for genome-wide DNA methylation profiling. The cell lines were derived from two HapMap populations: 'CEPH (Utah residents with ancestry from northern and western Europe)' (CEU) and 'Yoruba in Ibadan, Nigeria' (YRI).
Project description:Baseline microRNA (miRNA) expression was evaluated in 107 HapMap lymphoblastoid cell lines (LCLs; 53 CEU and 54 YRI) using Exiqon miRCURY LNA arrays v10.0 (Exiqon array). Total RNA from each of the 107 HapMap sample was labeled and hybridized onto an Exiqon array
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.