Project description:We used two RNA-Seq methods to measure the the global transcription levels in mouse liver cells. The data here provide insight into the pros and cons of whole transcript method and 3' RNA-Seq method.
Project description:Peripheral blood is an accessible and informative source of transcriptomal information for many human disease and pharmacogenomic studies. While there can be significant advantages to analyzing RNA isolated from whole blood, particularly in clinical studies, the preparation of samples for microarray analysis is complicated by the need to minimize artifacts associated with highly abundant globin RNA transcripts. The impact of globin RNA transcripts on expression profiling data can potentially be reduced by using RNA preparation and labeling methods that remove or block globin RNA during the microarray assay. We compared four different methods for preparing microarray hybridization targets from human whole blood collected in PAXGene tubes. Three of the methods utilized the Affymetrix one-cycle cDNA synthesis/in vitro transcription protocol but varied treatment of input RNA as follows: i. no treatment; ii. treatment with GLOBINclear; or iii. treatment with globin PNA oligos. In the fourth method cDNA targets were prepared with the Ovation amplification and labeling system. Results: We find that microarray targets generated with labeling methods that reduce globin mRNA levels or minimize the impact of globin transcripts during hybridization detect more transcripts in the microarray assay compared with the standard Affymetrix method. Comparison of microarray results with quantitative PCR analysis of a panel of genes from the NF-kappa B pathway shows good correlation of transcript measurements produced with all four target preparation methods, although method-specific differences in overall correlation were observed. The impact of freezing blood collected in PAXGene tubes on data reproducibility was also examined. Expression profiles show little or no difference when RNA is extracted from either fresh or frozen blood samples. Conclusion: RNA preparation and labeling methods designed to reduce the impact of globin mRNA transcripts can significantly improve the sensitivity of the DNA microarray expression profiling assay for whole blood samples. While blockage of globin transcripts during first strand cDNA synthesis with globin PNAs resulted in the best overall performance in this study, we conclude that selection of a protocol for expression profiling studies in blood should depend on several factors, including implementation requirements of the method and study design. RNA isolated from either freshly collected or frozen blood samples stored in PAXGene tubes can be used without altering gene expression profiles. Keywords: Whole Blood, Protocol Variation, Expression Profiling, Microarray, globin, PAXGene, PNA
Project description:Comparison of total RNA-seq and Affymetrix GeneChip(R) Human Transcriptome Array 2.0 analysis methods and Affymetrix GeneChip® WT PLUS Reagent and NuGEN Ovation® PICO WTA System V2 amplification methods for the detection of significant differentially expressed genes isolated from whole blood and brain RNA samples Affymetrix and NuGEN amplification methods are compared to determine which is most efficient, cost effective, and accurate in the detection of differentialy expressed transcript clusters on the HTA 2.0 microarray The optimum amplification microarray data is compared to total RNA-seq analysis of the same samples to determine which is the most efficient, cost effective, and accurate method of detecting differentially expressed genes
Project description:Strand-specific massively-parallel cDNA sequencing (RNA-Seq) is a powerful tool for novel transcript discovery, genome annotation, and expression profiling. Despite multiple published methods for strand-specific RNA-Seq, no consensus exists as to how to choose between them. Here, we developed a comprehensive computational pipeline for the comparison of library quality metrics from any RNA-Seq method. Using the well-annotated Saccharomyces cerevisiae transcriptome as a benchmark, we compared seven library construction protocols, including both published and our own novel methods. We found marked differences in complexity, strand-specificity, evenness and continuity of coverage, agreement with known annotations, and accuracy for expression profiling. Weighing each method’s performance and ease, we identify the dUTP second strand marking and the Illumina RNA ligation methods as the leading protocols, with the former benefitting from the availability of paired-end sequencing. Our analysis provides a comprehensive benchmark, and our computational pipeline is applicable for assessment of future protocols in any organism. Examination of 11 different strand-specific RNA-Seq libraries from 7 distinct methods; also 2 control non-strand-specific RNA-Seq libraries. To assess the performance of each strand-specific library in digital expression profiling, we compared them to reference expression measurements estimated from expression profiles using competitive hybridization of a mid-log RNA sample vs. genomic DNA using Agilent arrays.
Project description:Strand-specific massively-parallel cDNA sequencing (RNA-Seq) is a powerful tool for novel transcript discovery, genome annotation, and expression profiling. Despite multiple published methods for strand-specific RNA-Seq, no consensus exists as to how to choose between them. Here, we developed a comprehensive computational pipeline for the comparison of library quality metrics from any RNA-Seq method. Using the well-annotated Saccharomyces cerevisiae transcriptome as a benchmark, we compared seven library construction protocols, including both published and our own novel methods. We found marked differences in complexity, strand-specificity, evenness and continuity of coverage, agreement with known annotations, and accuracy for expression profiling. Weighing each method’s performance and ease, we identify the dUTP second strand marking and the Illumina RNA ligation methods as the leading protocols, with the former benefitting from the availability of paired-end sequencing. Our analysis provides a comprehensive benchmark, and our computational pipeline is applicable for assessment of future protocols in any organism.
Project description:Whole blood rather than purified peripheral blood mononuclear cells is likely to become the prime tissue using expression microarrays for disease predication or prognosis however excess of globin mRNA may reduce probe detection sensitivity. In our study, we assessed whether whole-blood or globin-reduced RNA gives the most robust and sensitive results to detect small gene expression changes in response to hormone replacement therapy exposure. Each sample (N = 12) were hybridized according to 3 different protocols: no globin reduction (controls), globin reduction using peptid nucleic acids (PNA) and using magnetic beads in the GlobinClear kit from Ambion. Finally, 7 and 4 technical replicates were conducted in no globin reduction and PNA groups, respectively. Both globin reduction approaches were mostly efficient at reducing globin RNA from cRNA. Samples processed by GlobinClear kit gave a very distinct gene expression profiles from the controls while samples processed with PNA gave an intermediary profile closest to the non globin reduction group with a slight increased sensitivity of transcript detection but a loss of reproducibility. Overall, no sign of higher sensitivity in detection of gene expression changes followed by hormone exposure was observed after globin reduction which was therefore judged not beneficial. Keywords: Groups comparaison To assess effect of globin reduction protocols on gene expression from whole-blood, we selected 12 postmenopausal women (6 HRT users and 6 non-HRT users) who were not using other medication than HRT at the time of blood sampling and in order to cover a wide body mass index (BMI) range in both HRT and non HRT users. The samples were also selected to contain the highest concentration of total extracted RNA. Each sample was hybridized according to 3 different protocols: no globin reduction (controls), globin reduction using PNAs, globin reduction using magnetic beads in the GlobinClear™ kit from Ambion. The reproducibility of the globin reduction method compared to the non globin reduction approach was investigated for the PNA method only since this method was the most effective and specific. We planned to conduct 7 technical replicates in each group (i.e. no globin reduction and PNA groups). During amplification process with PNA, 4 samples failed to reverse transcript long fragment of mRNA certainly due to inhibitory contamination and these arrays were therefore excluded from our analyses. One sample (sample 34) was amplified with PNA twice the same day to study technical reproducibility without amplification date effect. Finally, a total of 47 arrays were conducted including 7 and 4 technical replicates in no globin reduction and PNA group, respectively.