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Introductory RNA-seq Transcriptome Profiling
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Before we start: Align sequence reads to the reference genome The most time-consuming part of the analysis is doing the alignments of the reads (in Sanger fastq format) for all replicates against the reference genome.
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Overview: This training module is designed to provide a hands on experience in using RNA-Seq for transcriptome profiling. Question: How well is the annotated transcriptome represented in RNA-seq data in Arabidopsis WT and hy5 genetic backgrounds? How can we compare gene expression levels in the two samples? RNA-seq in the Discovery Environment
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Scientific Objective LONG HYPOCOTYL 5 (HY5) is a basic leucine zipper transcription factor (TF). Mutations in the HY5 gene cause aberrant phenotypes in Arabidopsis morphology, pigmentation and hormonal response. We will use RNA-seq to compare the transcriptomes of seedlings from WT and hy5 genetic backgrounds to identify HY5-regulated genes.
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Samples Experimental data downloaded from the NCBI Short Read Archive (GEO:GSM613465 and GEO:GSM613466) Two replicates each of RNA-seq runs for Wild- type and hy5 mutant seedlings.
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Specific Objectives By the end of this module, you should 1)Be more familiar with the DE user interface 2)Understand the starting data for RNA-seq analysis 3)Be able to align short sequence reads with a reference genome in the DE 4)Be able to analyze differential gene expression in the DE 5)Be able to use DE text manipulation tools to explore the gene expression data
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RNA-Seq Conceptual Overview Image source: http://www.bgisequence.com
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@SRR070570.4 HWUSI-EAS455:3:1:1:1096 length=41 CAAGGCCCGGGAACGAATTCACCGCCGTATGGCTGACCGG C + BA?39AAA933BA05>A@A=?4,9################# @SRR070570.12 HWUSI-EAS455:3:1:2:1592 length=41 GAGGCGTTGACGGGAAAAGGGATATTAGCTCAGCTGAATCT + @=:9>5+.5=?@ A?@6+2?:,%1/=0/7/>48## @SRR070570.13 HWUSI-EAS455:3:1:2:869 length=41 TGCCAGTAGTCATATGCTTGTCTCAAAGATTAAGCCATGCA + A;BAA6=A3=ABBBA84B AB2@>B@/9? @SRR070570.32 HWUSI-EAS455:3:1:4:1075 length=41 CAGTAGTTGAGCTCCATGCGAAATAGACTAGTTGGTACCAC + BB9?A@>AABBBB@BCA?A8BBBAB4B@BC71=?9;B:3B? @SRR070570.40 HWUSI-EAS455:3:1:5:238 length=41 AAAAGGGTAAAAGCTCGTTTGATTCTTATTTTCAGTACGAA + BBB?06-8BB@B17>9)=A91?>>8>*@ >@1:B>(B@ @SRR070570.44 HWUSI-EAS455:3:1:5:1871 length=41 GTCATATGCTTGTCTCAAAGATTAAGCCATGCATGTGTAAG + BBBCBCCBBBBBA@BBCCB+ABBCB@B@BB@:BAA@B@BB> @SRR070570.46 HWUSI-EAS455:3:1:5:1981 length=41 GAACAACAAAACCTATCCTTAACGGGATGGTACTCACTTTC + ?A>-?B;BCBBB@BC@/>A : Bioinformagician
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$ tophat -p 8 -G genes.gtf -o C1_R1_thout genome C1_R1_1.fq C1_R1_2.fq $ tophat -p 8 -G genes.gtf -o C1_R2_thout genome C1_R2_1.fq C1_R2_2.fq $ tophat -p 8 -G genes.gtf -o C1_R3_thout genome C1_R3_1.fq C1_R3_2.fq $ tophat -p 8 -G genes.gtf -o C2_R1_thout genome C2_R1_1.fq C1_R1_2.fq $ tophat -p 8 -G genes.gtf -o C2_R2_thout genome C2_R2_1.fq C1_R2_2.fq $ tophat -p 8 -G genes.gtf -o C2_R3_thout genome C2_R3_1.fq C1_R3_2.fq $ cufflinks -p 8 -o C1_R1_clout C1_R1_thout/accepted_hits.bam $ cufflinks -p 8 -o C1_R2_clout C1_R2_thout/accepted_hits.bam $ cufflinks -p 8 -o C1_R3_clout C1_R3_thout/accepted_hits.bam $ cufflinks -p 8 -o C2_R1_clout C2_R1_thout/accepted_hits.bam $ cufflinks -p 8 -o C2_R2_clout C2_R2_thout/accepted_hits.bam $ cufflinks -p 8 -o C2_R3_clout C2_R3_thout/accepted_hits.bam $ cuffmerge -g genes.gtf -s genome.fa -p 8 assemblies.txt $ cuffdiff -o diff_out -b genome.fa -p 8 –L C1,C2 -u merged_asm/merged.gtf \./C1_R1_thout/accepted_hits.bam,./C1_R2_thout/accepted_hits.bam,\./C1_R3_thout/accepted_hits.bam \./C2_R1_thout/accepted_hits.bam,\./C2_R3_thout/accepted_hits.bam,./C2_R2_thout/accepted_hits.bam Your RNA-Seq Data Your transformed RNA-Seq Data
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RNA-Seq Analysis Workflow Tophat (bowtie) Cufflinks Cuffmerge Cuffdiff CummeRbund Your Data iPlant Data Store FASTQ Discovery Environment Atmosphere
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Quick Summary Find Differentially Expressed genes Align to Genome: TopHat View Alignments: IGV Differential Expression: CuffDiff Download Reads from SRA Export Reads to FASTQ
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Import SRA data from NCBI SRA Extract FASTQ files from the downloaded SRA archives Pre-Configured: Getting the RNA-seq Data
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Examining Data Quality with fastQC
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RNA-Seq Workflow Overview
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Align the four FASTQ files to Arabidopsis genome using TopHat Step 1: Align Reads to the Genome Built-in ref. genomes User provided ref. genomes A single FASTQ file Folder with >= 1 FASTQ files
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TopHat TopHat is one of many applications for aligning short sequence reads to a reference genome. It uses the BOWTIE aligner internally. Other alternatives are BWA, MAQ, OLego, Stampy, Novoalign, etc.
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RNA-seq Sample Read Statistics Genome alignments from TopHat were saved as BAM files, the binary version of SAM (samtools.sourceforge.net/). Reads retained by TopHat are shown below Sequence runWT-1WT-2hy5-1hy5-2 Reads10,866,70210,276,26813,410,01112,471,462 Seq. (Mbase)445.5421.3549.8511.3
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Index BAM files using SAMtools Prepare BAM files for viewing
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Using IGV in Atmosphere 1.We already Launched an instance of NGS Viewers in Atmosphere 2.Use VNClient to connect to your remote desktop
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Pre-configured VM for NGS Viewers
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The Integrative Genomics Viewer (IGV) is a high-performance visualization tool for interactive exploration of large, integrated genomic datasets. It supports a wide variety of data types, including array-based and next-generation sequence data, and genomic annotations. Use IGV to inspect outputs from TopHat http://www.broadinstitute.org/igv/ Integrated Genomics Viewer (IGV)
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ATG44120 (12S seed storage protein) significantly down-regulated in hy5 mutant Background (> 9-fold p=0). Compare to gene on right lacking differential expression
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RNA-Seq Workflow Overview
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CuffDiff CuffLinks is a program that assembles aligned RNA-Seq reads into transcripts, estimates their abundances, and tests for differential expression and regulation transcriptome-wide. CuffDiff is a program within CuffLinks that compares transcript abundance between samples
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Examining Differential Gene Expression
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Examining the Gene Expression Data
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Filter CuffDiff results for up or down-regulated gene expression in hy5 seedlings Differentially expressed genes
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Example filtered CuffDiff results generated with the Filter_CuffDiff_Results to 1)Select genes with minimum two-fold expression difference 2)Select genes with significant differential expression (q <= 0.05) 3)Add gene descriptions
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Coming Soon: Downstream Analysis with cummeRbund
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Coming Soon: Support for Paired End Reads and Other Sequencing Platforms ?
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