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CRNA amplification methods enhance microarray identification of transcripts expressed in the nervous system

ABSTRACT: Background: DNA microarrays provide a powerful method for global analysis of gene expression. The application of this technology to specific cell types and tissues, however, is typically limited by small amounts of available mRNA, thereby necessitating amplification. Here we compare microarray results obtained with two different methods of RNA amplification to profile gene expression in the C. elegans larval nervous system. Results: We used the mRNA-tagging strategy to isolate transcripts specifically from C. elegans larval neurons. The WT-Ovation Pico System (WT-Pico) was used to amplify 2 ng of Pan-neural RNA to produce labeled cDNA for microarray analysis. These WT-Pico-derived data were compared to microarray results obtained with a labeled aRNA target generated by two rounds of In Vitro Transcription (IVT) of 25 ng of Pan-neural RNA. WT-Pico results in a higher fraction of Present calls than IVT, a finding consistent with the proposal that DNA-DNA hybridization results in lower mismatch signals than the RNA-DNA heteroduplexes produced by IVT amplification. Microarray data sets from these samples were compared to a Reference profile of all larval cells to identify transcripts with elevated expression in neurons. These results were validated by the high proportion of known neuron-expressed genes detected in these profiles and by promoter-GFP constructs for previously uncharacterized genes in these data sets. Together, the IVT and WT-Pico methods identified 2,173 unique neuron-enriched transcripts. Only about half of these transcripts (1,044), however, are detected as enriched by both IVT and WT-Pico amplification. Conclusion: We show that two different methods of RNA amplification, IVT and WT-Pico, produce valid microarray profiles of gene expression in the C. elegans larval nervous system with a low rate of false positives. However, our results also show that each method of RNA amplification detects a unique subset of bona fide neural-enriched transcripts and thus a wider array of authentic neural genes are identified by the combination of these data sets than by the microarray profiles obtained with either method of RNA amplification alone. With its relative ease of implementation and greater sensitivity, WT-Pico is the preferred method of amplification for cases in which sample RNA is limiting. Keywords: expression profile

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE9485 | GEO | 2007/11/01

SECONDARY ACCESSION(S): PRJNA103265

REPOSITORIES: GEO

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Project description:Background: DNA microarrays provide a powerful method for global analysis of gene expression. The application of this technology to specific cell types and tissues, however, is typically limited by small amounts of available mRNA, thereby necessitating amplification. Here we compare microarray results obtained with two different methods of RNA amplification to profile gene expression in the C. elegans larval nervous system. Results: We used the mRNA-tagging strategy to isolate transcripts specifically from C. elegans larval neurons. The WT-Ovation Pico System (WT-Pico) was used to amplify 2 ng of Pan-neural RNA to produce labeled cDNA for microarray analysis. These WT-Pico-derived data were compared to microarray results obtained with a labeled aRNA target generated by two rounds of In Vitro Transcription (IVT) of 25 ng of Pan-neural RNA. WT-Pico results in a higher fraction of Present calls than IVT, a finding consistent with the proposal that DNA-DNA hybridization results in lower mismatch signals than the RNA-DNA heteroduplexes produced by IVT amplification. Microarray data sets from these samples were compared to a Reference profile of all larval cells to identify transcripts with elevated expression in neurons. These results were validated by the high proportion of known neuron-expressed genes detected in these profiles and by promoter-GFP constructs for previously uncharacterized genes in these data sets. Together, the IVT and WT-Pico methods identified 2,173 unique neuron-enriched transcripts. Only about half of these transcripts (1,044), however, are detected as enriched by both IVT and WT-Pico amplification. Conclusion: We show that two different methods of RNA amplification, IVT and WT-Pico, produce valid microarray profiles of gene expression in the C. elegans larval nervous system with a low rate of false positives. However, our results also show that each method of RNA amplification detects a unique subset of bona fide neural-enriched transcripts and thus a wider array of authentic neural genes are identified by the combination of these data sets than by the microarray profiles obtained with either method of RNA amplification alone. With its relative ease of implementation and greater sensitivity, WT-Pico is the preferred method of amplification for cases in which sample RNA is limiting. Experiment Overall Design: We profiled gene expression throughout the nervous system of the model organism Caenorhabditis elegans using two different amplification methods, WT-Pico and IVT (in vitro transcription). Since postembryonic cells are unattainable via this method, we used mRNA-tagging to isolate pan-neural RNAs from larval animals. In short, an epitope tagged poly-A binding protein (FLAG-PAB-1) was driven in all neurons using the F25B3.3 promoter. We then amplified harvested RNA using IVT or WT-Pico. Data generated from this study reveals significant differences between the two amplification methods. However, both seem to identify bona fide neural transcripts. Our work suggests that using two amplification methods, when possible, will provide one with a more accurate view of transcription in a particular cell type.

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. Evaluation of each amplification system consisted of three biological replicates per treatment (control root cells or giant cells) with one biological replicate split into three technical replicates for a total of 10 samples per amplification procedure. RNA samples for amplification with the NuGEN WT-Ovation Pico kit were isolated from 150 control cells or from 80 giant cells using the PicoPure RNA Isolation Kit (Arcturus, Mountain View, USA). For amplification with the NuGEN WT-Ovation One-Direct kit, samples containing 150 control or 80 giant cells were collected directly into 2ul of the NuGEN lysis buffer. RNA amplifications were carried out according to the respective kitsâ?? protocols.

Project description:Purpose: The goals of this study is to determine the best method of gene expression quantification (RNA-seq, Microarray, NanoString) and amplification kits adapted to low-input and/or low-quality RNA samples (FFPE samples) Methods: Mouse bladder cancer cell line (mouse bladder cancer cell line, BC57) and mouse normal mouse normal urothelium were fixed in formalin and embedded in paraffin (FFPE), andfesh frozen (FF) in liquid nitrogen. The total RNA of these 4 samples were tested by 3 technologies (NanoString, RNA-seq and Microarray) and the results were compared to its reference (high-quality and high-input RNA of mouse bladder cancer cell line and mouse normal mouse normal urothelium). For NanoString with low-input RNA samples, each sample was tested by NanoString quantification after amplification by SMARTer Stranded Total RNA-Seq Kit - Pico Input mammelian and Ovation SoLo NuGEN RNA-seq System, and NanoString based on PCR approach with three input quantities: 50pg, 250pg and 2ng of total RNA, except for NanoString quantification after amplification by SMARTer Stranded Total RNA-Seq Kit - Pico Input mammelian kit for which the minimum recommended quantity was 250pg of total RNA. NanoString direct quantification was also done for FF and FFPE samples at high amount (50ng of total RNA) and results obtained from FF samples were considered as the reference. To determine which is the method for NanoString technology, low-input and low-quality RNA samples, we performed NanoString control quality metrics, principal component analysis, and a differential analysis between the mouse bladder cancer cell lines and the mouse normal mouse normal urothelium for each input quantity, amplification method and method of sample preservation (FF or FFPE). Results: The NanoString based PCR based approach is recommended for quantification of gene expression of FFPE and FF samples from 250pg of total RNA. However, NanoString quantification after amplification by SMARTer Stranded Total RNA-Seq Kit - Pico Input mammelian and Ovation SoLo NuGEN RNA-seq System is not recommended for FF and FFPE from low-input samples.

Project description:Background: Standard Guthrie cards have been widely used to collect blood samples from neonates for newborn screening programs, and to a lesser extent, from normal controls and patients in research studies. Ease of blood collection (small quantity and less pain), transportation, and storage are the advantages of using these cards. It is believed that RNA obtained from these samples is of low quantity and degraded quality. However, we recently discovered that approximately 3,500 expressed genes can be detected from blood spot samples using in-house made, low resolution cDNA microarrays. Here, we established a new and improved methodology to acquire gene expression profiles from blood spot cards using commercially-available high resolution microarrays. We determined the optimal number of blood spot punches required for maximal RNA extraction, eliminated uses of trizol and chloroform for RNA extraction by using a modified protocol of the illustra Mini Spin Kit from GE-Whatm an, concentrated the quantity of RNA templates before amplification, improved amplification efficiency using the new Ribo-SPIA technology in WT-Ovation Pico System (WT-Pico) by NuGEN, before the samples were hybridized onto 4x44K whole human genome gene expression microarrays from Agilent. Nine dried blood spot samples were collected from a control population and stored at ~ -80 °C between 6 months to 2 years. High quality RNA was extracted from the buffy coat of the same individuals as a reference and processed using the standard Agilent microarray procedure. Commercially-available brain RNA was used as a positive control in both standard and new procedures for microarrays. Results: Three 3-mm punches produced the highest yield of total RNA using the non-trizol extraction method. Three to six nanogram per microliter of RNA can be concentrated and is sufficient to be amplified using the WT-Pico. Approximately 9,000 expressed genes can be detected after normalization and background correction of the microarray data. Conclusion: Genome-wide gene expression profile can be obtained from archived dried blood spot samples. Our new and improved methodology will add value to the perception of utilizing archival Guthrie cards eg. neonatal blood spot cards as unique biospecimens for molecular genomics and diagnostic studies of perinatal diseases such as pediatric cancers. Keywords: Gene Expression experiment

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CRNA amplification methods enhance microarray identification of transcripts expressed in the nervous system

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