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Extreme clonality in lymphoblastoid cell lines with implications for allele specific expression analyses.

ABSTRACT: Lymphoblastoid cell lines (LCL) are being actively and extensively used to examine the expression of specific genes and genome-wide expression profiles, including allele specific expression assays. However, it has recently been shown that approximately 10% of human genes exhibit random patterns of monoallelic expression within single clones of LCLs. Consequently allelic imbalance studies could be significantly compromised if bulk populations of donor cells are clonal, or near clonal. Here, using X chromosome inactivation as a readout, we confirm and quantify widespread near monoclonality in two independent sets of cell lines. Consequently, we recommend where possible the use of bulk, non cell line, ex vivo cells for allele specific expression assays.

SUBMITTER: Plagnol V

PROVIDER: S-EPMC2494943 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Extreme clonality in lymphoblastoid cell lines with implications for allele specific expression analyses.

Plagnol Vincent V Uz Elif E Wallace Chris C Stevens Helen H Clayton David D Ozcelik Tayfun T Todd John A JA

PloS one 20080813 8

Lymphoblastoid cell lines (LCL) are being actively and extensively used to examine the expression of specific genes and genome-wide expression profiles, including allele specific expression assays. However, it has recently been shown that approximately 10% of human genes exhibit random patterns of monoallelic expression within single clones of LCLs. Consequently allelic imbalance studies could be significantly compromised if bulk populations of donor cells are clonal, or near clonal. Here, using ...[more]

PMID: 18698422

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Project description:BackgroundStatins are widely prescribed to lower plasma low-density lipoprotein cholesterol levels. Though statins reduce cardiovascular disease risk overall, statin efficacy varies, and some people experience adverse side effects while on statin treatment. Statins also have pleiotropic effects not directly related to their cholesterol-lowering properties, but the mechanisms are not well understood. To identify potential genetic modulators of clinical statin response, we looked for genetic variants associated with statin-induced changes in gene expression (differential eQTLs or deQTLs) in lymphoblastoid cell lines (LCLs) derived from participants of the Cholesterol and Pharmacogenetics (CAP) 40 mg/day 6-week simvastatin clinical trial. We exposed CAP LCLs to 2 μM simvastatin or control buffer for 24 h and performed polyA-selected, strand-specific RNA-seq. Statin-induced changes in gene expression from 259 European ancestry or 153 African American ancestry LCLs were adjusted for potential confounders prior to association with genotyped and imputed genetic variants within 1 Mb of each gene's transcription start site.ResultsFrom the deQTL meta-analysis of the two ancestral populations, we identified significant cis-deQTLs for 15 genes (TBC1D4, MDGA1, CHI3L2, OAS1, GATM, ASNSD1, GLUL, TDRD12, PPIP5K2, OAS3, SERPINB1, ANKDD1A, DTD1, CYFIP2, and GSDME), eight of which were significant in at least one of the ancestry subsets alone. We also conducted eQTL analyses of the endogenous (control-treated), statin-treated, and average of endogenous and statin-treated LCL gene expression levels. We identified eQTLs for approximately 6000 genes in each of the three (endogenous, statin-treated, and average) eQTL meta-analyses, with smaller numbers identified in the ancestral subsets alone.ConclusionsSeveral of the genes in which we identified deQTLs have functions in human health and disease, such as defense from viruses, glucose regulation, and response to chemotherapy drugs. This suggests that DNA variation may play a role in statin effects on various health outcomes. These findings could prove useful to future studies aiming to assess benefit versus risk of statin treatment using individual genetic profiles.

Project description:AimFolate is vital for cell growth and development through its important role in one-carbon metabolism - an essential process in the synthesis of amino acids and nucleic acids. Folate pathway genes have been considered as therapeutic targets of drugs for the treatment of cancer and other diseases. Racial and ethnic disparities of folate metabolism and outcome of antifolate therapies have been reported. In this study, we evaluate the genetic regulation for expression and alternative splicing of folate related genes in HapMap lymphoblastoid cell lines (LCLs) of individuals of European and African descent.Materials & methodsGene and exon level expression and alternative splicing of folate pathway genes were compared in LCLs derived from the Centre d'Etude du Polymorphisme Humain (CEPH) from Utah (CEU) and the Yoruba from Ibadan (YRI) using a permutation-based test. A genome-wide association study was performed to search for SNPs associated with folate pathway gene expressions and alternative splicing in the combined population samples.ResultsA total of 52 folate pathway genes were evaluated in the analysis of which 46 were expressed in the LCLs. There were 12 genes (26%) with differential gene-level expression and 23 genes (50%) with differential alternative splicing for exons or UTRs between the CEU and the YRI (permutation p <or= 0.05). The expression level of FPGS and the splicing indices of eight genes (ATP13A2, ASCC3L1, IFIH1, SMARCA5, SMARCA2, SETX, DDX52 and RUVBL2) were found to be associated with SNP genotypes in the combined populations (p < 3.2 x 10(-8), Bonferroni corrected p < 0.05).ConclusionOur study suggests that LCLs are an in vitro system suitable to evaluate the expression levels of folate pathway genes. The differential transcript-level expressions and the differentially alternative splicing events of exons or UTRs and associated SNP markers in 2 populations will enhance our understanding of the folate pathway and, thus, facilitate research in the areas of nutrition and folate metabolism.

Dataset Information

Extreme clonality in lymphoblastoid cell lines with implications for allele specific expression analyses.

Publications

Extreme clonality in lymphoblastoid cell lines with implications for allele specific expression analyses.

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