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 microarray experiments starting with nanogram amounts of RNA it is essential to implement reproducible and powerful RNA amplification techniques. Available methods were mainly tested for reproducibility, only a few studies concentrated on potential amplification bias. We evaluated three amplification protocols, which are less time-consuming than the commonly used T7-RNA polymerase based in vitro transcription protocols and therefore may be more suitable for clinical use: Template Switching (TS)-PCR (SMART-PCR Kit, BD), Ribo-SPIA (single primer isothermal amplification, Oviation, Nugen) and a random primer-based PCR. Additionally a more sensitive labeling method, Dendrimer-labeling (Genisphere), was evaluated. All methods were compared to unamplified RNA labelled at reverse transcription. Hybridizations were carried out on a targeted two-colour oligonucleotide microarray. From our results we conclude that RNA amplification with TS-PCR is highly reproducible and results in a reliable representation of the starting RNA population. We then assessed whether RNA amplification of clinical breast and thyroid cancer samples with TS-PCR showed robust performance when altered cycle numbers or partially degraded RNA were used. According to our experiments TS-PCR proved to be a very reliable method for global RNA amplification, even when starting from partially degraded RNA down to a RNA Integrity Number (RIN) of 4.3. Keywords: microarray expression profiling, RNA amplification techniques, RNA integrity
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:Genome-wide profiling of transcription factors based on massive parallel sequencing of immunoprecipitated chromatin (ChIP-seq) requires nanogram amounts of DNA. Here we describe a high-fidelity, single-tube linear DNA amplification method (LinDA) for ChIP-seq and reChIP-seq with picogram DNA amounts obtained from a few thousand cells. This amplification technology will facilitate global analyses of transcription-factor binding and chromatin with very small cell populations, such as stem or cancer-initiating cells.
Project description:Genome-wide profiling of transcription factors based on massive parallel sequencing of immunoprecipitated chromatin (ChIP-seq) requires nanogram amounts of DNA. Here we describe a high-fidelity, single-tube linear DNA amplification method (LinDA) for ChIP-seq and reChIP-seq with picogram DNA amounts obtained from a few thousand cells. This amplification technology will facilitate global analyses of transcription-factor binding and chromatin with very small cell populations, such as stem or cancer-initiating cells. In total 5 samples were generated from the F9 teratocarcinoma cell system: mRXRa-RARg-LinDA;mRXRa_100xfold-diluted_LinDA; mRXRa(1) and two others previously described in GSE30538 (mRXRa(2): !Series_sample_id=GSM757796; mRARg : !Series_sample_id=GSM757803). In addition, 14 samples were generated from the H3396 breast cancer cell system. Those samples containing the label "LinDA" has been amplified following the Linear DNA amplification method developed by Pattabhiraman et al. ((2011), Nature Methods 8, 565-67) prior library preparation for Solexa sequencing.
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: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:Methylation-based liquid biopsies show promise in detecting cancer from circulating cell-free DNA, but current limitations impede clinical application. Most assays necessitate substantial DNA inputs, posing challenges. Underrepresented tumor DNA fragments may go undetected during exponential amplification steps of traditional sequencing methods. Here we report LABS (Linear Amplification based Bisulfite Sequencing), enabling linear amplification of bisulfite-treated DNA fragments in a genome-wide, unbiased fashion, detecting cancer abnormalities with sub-nanogram inputs. Applying LABS to 100 patient samples revealed cancer-specific patterns, copy number alterations, and enhanced cancer detection accuracy by identifying tissue-of-origin and immune cell composition.