| 1. |
- Ghotbi, Roza, et al.
(author)
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Allele-specific expression and gene methylation in the control of CYP1A2 mRNA level in human livers
- 2009
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In: The Pharmacogenomics Journal. - : Springer Science and Business Media LLC. - 1470-269X .- 1473-1150. ; 9:3, s. 208-217
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Journal article (peer-reviewed)abstract
- The basis for interindividual variation in the CYP1A2 gene expression is not fully understood and the known genetic polymorphisms in the gene provide no explanation. We investigated whether the CYP1A2 gene expression is regulated by DNA methylation and displays allele-specific expression (ASE) using 65 human livers. Forty-eight percent of the livers displayed ASE not associated to the CYP1A2 mRNA levels. The extent of DNA methylation of a CpG island including 17 CpG sites, close to the translation start site, inversely correlated with hepatic CYP1A2 mRNA levels (P=0.018). The methylation of two separate core CpG sites was strongly associated with the CYP1A2 mRNA levels (P=0.005) and ASE phenotype (P=0.01), respectively. The CYP1A2 expression in hepatoma B16A2 cells was strongly induced by treatment with 5-aza-2'-deoxycytidine. In conclusion, the CYP1A2 gene expression is influenced by the extent of DNA methylation and displays ASE, mechanisms contributing to the large interindividual differences in CYP1A2 gene expression.
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| 2. |
- Milani, Lili, et al.
(author)
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Allele-specific gene expression patterns in primary leukemic cells reveal regulation of gene expression by CpG site methylation
- 2009
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In: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 19:1, s. 1-11
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Journal article (peer-reviewed)abstract
- To identify genes that are regulated by cis-acting functional elements in acute lymphoblastic leukemia (ALL) we determined the allele-specific expression (ASE) levels of 2, 529 genes by genotyping a genome-wide panel of single nucleotide polymorphisms in RNA and DNA from bone marrow and blood samples of 197 children with ALL. Using a reproducible, quantitative genotyping method and stringent criteria for scoring ASE, we found that 16% of the analyzed genes display ASE in multiple ALL cell samples. For most of the genes, the level of ASE varied largely between the samples, from 1.4-fold overexpression of one allele to apparent monoallelic expression. For genes exhibiting ASE, 55% displayed bidirectional ASE in which overexpression of either of the two SNP alleles occurred. For bidirectional ASE we also observed overall higher levels of ASE and correlation with the methylation level of these sites. Our results demonstrate that CpG site methylation is one of the factors that regulates gene expression in ALL cells.
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| 3. |
- Milani, Lili, 1981-
(author)
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Gene Expression in Cancer Cells : Detection of Splice Variants, Allele-specific Expression and DNA Methylation
- 2009
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Doctoral thesis (other academic/artistic)abstract
- The human genome sequencing project has provided a wealth of information on sequence variation between individuals. The surprisingly low number of genes in the human genome is compensated for by a complex regulation of gene expression. New methods are now being developed for the discovery and analysis of the regulatory regions of the genome to elucidate factors that affect both normal and disease-associated human genetic variation. In parallel with identification of DNA sequence variation, efforts are being made to unravel the next layer of information - epigenetic modifications of the genome. The studies in this thesis describe the application of methods for genotyping single nucleotide polymorphisms (SNPs) in DNA for the analysis of gene transcripts in cancer cells. We performed quantitative analysis of splice variants and screened for allele-specific gene expression (ASE) in cancer cells using the tag-microarray based minisequencing system. This analysis revealed transcript isoforms that were differentially spliced in leukemia cell lines and normal endothelial cell lines. We detected wide-spread allele-specific gene expression in cancer cells that were sensitive or resistant to anti-cancer drugs. In regulatory regions of the genes with ASE we identified putative regulatory SNPs. Using technology developed for large-scale SNP genotyping, we screened for ASE in an internationally unique collection of childhood acute lymphoblastic leukemia (ALL) samples. Analysis of DNA methylation in promoter regions of genes displaying ASE revealed genes, whose expression is regulated by allele-specific DNA methylation. For a subset of these genes we found a correlation between DNA methylation levels and probability of disease-free survival in ALL patients with different chromosomal aberrations. The methylation patterns that we identified constitute excellent candidate markers for subtyping of ALL patients and for stratification of ALL patients based on their probability of disease-free survival and response to drug treatment. The results of this study have increased our understanding of epigenetic changes in ALL cells and will hopefully help to design better treatment plans for the patients to avoid over-treatment and unnecessary side effects.
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| 4. |
- Mukonzo, Jackson K, et al.
(author)
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A novel polymorphism in ABCB1 gene, CYP2B6*6 and sex predict single-dose efavirenz population pharmacokinetics in Ugandans.
- 2009
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In: British journal of clinical pharmacology. - : Wiley. - 1365-2125 .- 0306-5251. ; 68:5, s. 690-9
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Journal article (peer-reviewed)abstract
- AIMS: Efavirenz exhibits pharmacokinetic variability causing varied clinical response. The aim was to develop an integrated population pharmacokinetic/pharmacogenetic model and investigate the impact of genetic variations, sex, demographic and biochemical variables on single-dose efavirenz pharmacokinetics among Ugandan subjects, using NONMEM. METHODS: Efavirenz plasma concentrations (n = 402) from 121 healthy subjects were quantified by high-performance liquid chromatography. Subjects were genotyped for 30 single nucleotide polymorphisms (SNPs), of which six were novel SNPs in CYP2B6, CYP3A5 and ABCB1. The efavirenz pharmacokinetics was described by a two-compartment model with zero- followed by first-order absorption. RESULTS: Apparent oral clearance (95% confidence interval) was 4 l h l(-1) (3.5, 4.5) in extensive metabolizers. In the final model, incorporating multiple covariates, statistical significance was found only for CYP2B6*6 and CYP2B6*11 on apparent oral clearance as well as ABCB1 (rs3842) on the relative bioavailability. Subjects homozygous for CYP2B6*6 (G516T, A785G) and *11 displayed 21 and 20% lower apparent oral clearance, respectively. Efavirenz relative bioavailability was 26% higher in subjects homozygous for ABCB1 (rs3842). The apparent peripheral volume of distribution was twofold higher in women compared with men. CONCLUSIONS: The model identified the four factors CYP2B6*6, CYP2B6*11, a novel variant allele in ABCB1 (rs3842) and sex as major predictors of efavirenz plasma exposure in a healthy Ugandan population after single-dose administration. Use of mixed-effects modelling allowed the analysis and integration of multiple pharmacogenetic and demographic covariates in a pharmacokinetic population model.
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