Project description:Our aim was to identify which stand alone amplification protocol performed best in our lab when the starting amount of total RNA was limited to 50 ng (A typical amount of total RNA we obtained by laser capture microdissection of tissues from silique samples). Since the quality of extracted RNA is very often tissue dependent and will affect the amplification efficiency, we decided to use total RNA extracted from whole siliques; better representing tissues targeted by LCM. We set out to compare two basic methods of RNA amplification, based on IVT and PCR. Keywords: Comparison of target preparation regimes from limiting amounts of RNA
Project description:For more than a decade, microarrays have been a powerful and widely used tool to explore the transcriptome of biological systems. However, the amount of biological material from cell sorting or laser capture microdissection is much too small to perform microarray studies. To address this issue, RNA amplification methods have been developed to generate sufficient targets from picogram amounts of total RNA to perform microarray hybridisation. In this study, four commercial protocols for amplification of picograms amounts of input RNA for microarray expression profiling were evaluated and compared. The quantitative and qualitative performances of the methods were assessed. Microarrays were hybridised with the amplified targets and the amplification protocols were compared with respect to the quality of expression profiles, reproducibility within a concentration range of input RNA, and sensitivity.
Project description:We tested the performance of three methods for amplifying single-cell amounts of RNA under ideal conditions: T7-based in vitro transcription; switching mechanism at 5' end of RNA template (SMART) PCR amplification; and global PCR amplification. All methods introduced amplification-dependent noise when mRNA was amplified 108-fold, compared with data from unamplified cDNA. PCR-amplified cDNA demonstrated the smallest number of differences between two parallel replicate samples and the best correlation between independent amplifications from the same cell type, with SMART outperforming global PCR amplification. SMART had the highest true-positive rate and the lowest false-positive rate when comparing expression between two different cell types, but had the lowest absolute discovery rate of all three methods. Direct comparison of the performance of SMART and global PCR amplification on single-cell amounts of total RNA and on single neural stem cells confirmed these findings. Under the conditions tested, PCR amplification was more reliable than linear amplification for detecting true expression differences between samples. SMART amplification had a higher true-positive rate than global amplification, but at the expense of a considerably lower absolute discovery rate and a systematic compression of observed expression ratios. Keywords: Oliginucleotide expression microarrays, T7-based linear amplification; SMART PCR-based amplification; global PCR amplification
Project description:For more than a decade, microarrays have been a powerful and widely used tool to explore the transcriptome of biological systems. However, the amount of biological material from cell sorting or laser capture microdissection is much too small to perform microarray studies. To address this issue, RNA amplification methods have been developed to generate sufficient targets from picogram amounts of total RNA to perform microarray hybridisation. In this study, four commercial protocols for amplification of picograms amounts of input RNA for microarray expression profiling were evaluated and compared. The quantitative and qualitative performances of the methods were assessed. Microarrays were hybridised with the amplified targets and the amplification protocols were compared with respect to the quality of expression profiles, reproducibility within a concentration range of input RNA, and sensitivity. Four commercial protocols for amplification of picograms amounts of input RNA for microarray expression profiling were evaluated and compared. For each protocol, one RNA amplification was performed from 250 pg, and one from 500 pg of human universal RNA by two operators in two independent laboratories and compared to the amplified aRNA obtained from 2 µg and 100 ng RNA inputs following the standard protocol proposed by Affymetrix. A negative control (amplification without total RNA) and a positive control (if available) were included in each experimental batch. Samples indicating 50, 100, and 1000 pg RNA inputs correspond to 3 additional quantities of total RNA used to synthesise the cDNA target using the nugen protocol for comparison (250, 500 pg + 50, 100, 1000 pg).
Project description:Differential gene expression between groups of homogenous cell types is a biological question whose time has come. RNA can be extracted from small numbers of cells, such as those isolated by laser capture microdissection, but the small amounts obtained often require amplification to enable whole genome transcriptome profiling by technologies such as microarray analysis and RNA-seq. Recently, advances in amplification procedures make amplification directly from whole cell lysates possible. The aim of this study was to compare two amplification systems for variations in observed RNA abundance attributable to the amplification procedure for use with small quantities of cells isolated by laser capture microdissection. Arabidopsis root cells undergoing giant cell formation due to nematode infestation and un-infested control root cells were laser captured and used to evaluate 2 amplification systems. One, NuGEN's WT-Ovation Pico amplification system, uses total RNA as starting material while the other, NuGEN's WT-One-Direct Amplification system, uses lysate containing the captured cells. The reproducibility of whole genome transcript profiling and correlations of both systems were investigated after microarray analysis. The NuGEN WT-Ovation One-Direct system was less reproducible and more variable than the NuGEN WT-Ovation Pico system. The NuGEN WT-Ovation Pico Amplification kit resulted in the detection of thousands of genes differentially expressed genes between giant cells and control cells. This is in marked contrast to the relatively few genes detected after amplification with the NuGEN WT-Ovation One-Direct Amplification kit.
Project description:Conventional prokaryotic RNA labeling method usually requires large amounts of starting materials and tends to generate high background signals. Recently, two novel methods based on amplification systems were introduced. Here, we compared three alternative strategies: direct labeling method, ployadenylation-involved oligo-dT priming amplification method and random priming amplification method (hereafter referred to as DL, PAOD and RPA method in this article) for prokaryotic RNA labeling employing the expression profiling investigation in Escherichia coli (E. coli) heat shock model.