Presentation on theme: "Vanderbilt Center for Quantitative Sciences Summer Institute Sequencing Analysis Yan Guo."— Presentation transcript:
Vanderbilt Center for Quantitative Sciences Summer Institute Sequencing Analysis Yan Guo
What is Sequencing? Sequencing is the process of determining the precise order of nucleotides. Non high throughput sequencing: Sanger Sequencing: The basic chain termination method, developed by Frederick Sanger in Generates all possible single-stranded DNA molecules complementary to a given template, and beginning at a common 5' base.
The Pros and Cons of Sanger Sequencing Pros: Highly accurate targetable Cons: Cost $15 per /1000 base pairs, to sequencing the whole genome will cost roughly: 30bil/1000x$15=$15m Low detection rate of alternative allele
Current Generation Sequencing IlluminaABI Solid454 Life Science PriceLowmediumHigh Read Length Read DepthHigh Low DifficultyEasyHighEasy
Sequencing Type By Source RNA: mRNA, Small RNA, Total RNA DNA: Whole Genome or targeted (Exome, mitochondrial, genes of interest, etc)
Sequencing Data Raw Image data is more than 2TB per sample Raw data is about 5-15GB per single end sample or 10-30GB per pair end sample for RNAseq or Exome Sequencing. Whole genome data can easily exceed 200GB per sample. In general 5x raw data size is needed to finish processing Raw data is usually in FASTQ format, the base quality is in Phred scale Older Illumina pipeline uses Phred 64 scale, newer CASAVA 1.8 pipeline uses Sanger scale.
Single end vs Paired end Paired end data has double amount of data than single end. Paired end is more expensive than single end. Paired end data is easier to do quality control (insert size, removing duplicate) Paired end data provides more opportunities to detect structural variance.
What can you obtain from DNAseq SNPs (require only normal or tumor) Somatic Mutations (require tumor and normal pair) Copy Number Variation (work best with whole genome sequencing) Small Structural Variance: Insertion, deletion Large Structure Variance: (Translocation, Inversion)
What can you obtain from RNAseq Gene Expression SNP (only for expressed genes) Novel Splicing Variants Genes Fusion RNAseq has been used primarily as a replacement of microarray
How does RNAseq compare to Microarray? Since 2008, people has been saying that RNAseq will replace microarray for gene expression profiling. VANTAGE stopped offering microarray service earlier this year. Wang, Z., M. Gerstein, and M. Snyder, RNA-Seq: a revolutionary tool for transcriptomics. Nat Rev Genet, (1): p Shendure, J., The beginning of the end for microarrays? Nat Methods, (7): p
Data Distribution Guo, Y., et al., Large Scale Comparison of Gene Expression Levels by Microarrays and RNAseq Using TCGA Data. PLoS One, (8): p. e71462.
Result Consistency Guo, Y., et al., Large Scale Comparison of Gene Expression Levels by Microarrays and RNAseq Using TCGA Data. PLoS One, (8): p. e71462.
RNAseq vs Microarray - advantages RNAseqMiroarray Result Type Rich, not limited to expressionLimited to expression only Expression Can quantify expression on exon and gene levelCan quantify expression on exon or gene level Novel Discovery Can be used for novel discovery Can only detect what is on the chip Analysis DifficultEasy Interpretation DifficultEasy Price for assay Price has become comparable to microarray, however the analysis hardware and analysis time may increase the final cost Price is stable
Raw 1:N:0:ATCACG NTGGAGTCCTAGGCACAGCTCTAAGCCTCCTTATTCGAGCCGAGCTGGGCC +
@EAS139:136:FC706VJ:2:2104:15343: :Y:18:ATCACG EAS139the unique instrument name 136the run id FC706VJthe flowcell id 2flowcell lane 2104tile number within the flowcell lane 'x'-coordinate of the cluster within the tile 'y'-coordinate of the cluster within the tile 1 the member of a pair, 1 or 2 (paired-end or mate-pair reads only) Y Y if the read fails filter (read is bad), N otherwise 18 0 when none of the control bits are on, otherwise it is an even number ATCACGindex sequence
Phred Score Phred Quality Score Probability of incorrect base call Base call accuracy 101 in 1090 % 201 in % 301 in % 401 in % 501 in %
Quality Control Quality control should be conducted at multiple steps during sequencing data processing – Raw data – Alignment – Results (Expression for RNA, and SNP/mutation for DNA) Guo, Y., et al., Three-stage quality control strategies for DNA re-sequencing data. Brief Bioinform, 2013.
Raw Data QC - Tools FAST QC rojects/fastqc/ rojects/fastqc/ FASTX-Toolkit QC3 https://github.com/slzhao/QC3https://github.com/slzhao/QC3 NGS QC Toolkit
Clustering Algorithms Start with a collection of n objects each represented by a p–dimensional feature vector x i, i=1, …n. The goal is to divide these n objects into k clusters so that objects within a clusters are more “similar” than objects between clusters. k is usually unknown. Popular methods: hierarchical, k-means, SOM, mixture models, etc.
Distance Calculation in Microarray Pearson Correlation Two profiles (vectors) and +1 Pearson Correlation – 1
Similarity Measurements Euclidean Distance
Linkage Single Linkage: D(X, Y) = min(d(x, y)), x ϵ X, y ϵ Y Complete Linkage: D(X, Y) = max(d(x, y)), x ϵ X, y ϵ Y Average Linkage:
Experssion QC - What to Look For
Correction of Batch Effect Guo, Y., et al., Statistical strategies for microRNAseq batch effect reduction. Translational Cancer Research, (3): p
Normalization of RNAseq Reads Per Kilo base per Million reads (RPKM)
RNAseq Data Alignment TopHat2 ml ml MapSplice ice ice
Gene Quantification CufflInks for RPKM HTSeq for read count huber.embl.de/users/anders/HTSeq/doc/over view.htmlhttp://www- huber.embl.de/users/anders/HTSeq/doc/over view.html
Data Gene Symbol DDR RFC HSPA PAX GUCA1A UBE1L THRA PTPN CCL CYP2E EPHB ESRRA CYP2A SCARB TTLL C2orf WFDC MAPK MAPK ADAM
Example of Quantile Normalization S1S2S3 G1244 G25414 G3468 G4358 G5339 S Red = G1; Green = G2; Blue = G3; Yellow = G4; Black = G5 Original Sort S1 S Sort S2 S Sort S3 S1S2S3 G1234 G2348 G3348 G4459 G55614 Sorted
Take Average for Each Row S1S2S Sorted S1S2S3 333 S1S2S S1S2S S1S2S S1S2S Averaged
Reorder S1S2S3 353 S1S2S Averaged S1S2S Red = G1; Green = G2; Blue = G3; Yellow = G4; Black = G5 S1S2S S1S2S S1S2S
Differential Expression Analysis Cuffdiff from Cufflinks package Trapnell, C., et al., Differential gene and transcript expression analysis of RNA-seq experiments with TopHat and Cufflinks. Nat Protoc, (3): p DESeq EdgeR tml tml NBPSeq project.org/web/packages/NBPSeq/index.htmlhttp://cran.r- project.org/web/packages/NBPSeq/index.html TSPM de/tspm-r-s2496.htmlhttp://omictools.com/sequencing/rna-seq/normalization- de/tspm-r-s2496.html baySeq html html
Which Method Is the Best? Guo, Y., et al., Evaluation of read count based RNAseq analysis methods. BMC Genomics, Suppl 8: p. S2.
Combined Approach Guo, Y., et al., MultiRankSeq: Multiperspective Approach for RNAseq Differential Expression Analysis and Quality Control. BioMed Research International, : p. 8. log2FoldChan ge(DESeq2) pValue(DESe q2)pAdj(DESeq2) log2FoldChan ge(edgeR) pValue(edge R)pAdj(edgeR) log2FoldChan ge(raw) 1- Likelihood(ba ySeq) AdjLikelihood (baySeq)rank(DESeq)rank(edgeR)rank(baySeq)rankMethod1 ENSMUSG _Rps E E E E E E ENSMUSG _Rpl23a E E E E E E ENSMUSG _Gm E E E E E E ENSMUSG _Atp5g E E E E E E ENSMUSG _Gm E E E E E ENSMUSG _Gm E E E E E E ENSMUSG _Rpl E E E E ENSMUSG _Rpl E E E E ENSMUSG _Rpl E E E E ENSMUSG _Gm E E E E E E ENSMUSG _Mup E E E E E ENSMUSG _Mir E E E E ENSMUSG _Rps E E E E
Presentation Using Heatmap and Cluster Zhao, S., et al., Advanced Heat Map and Clustering Analysis Using Heatmap3. BioMed Research International, : p. 6.
Difference Between Heatmaps
Questions We Can Answer with Cluster Microarray data quality checking – Does replicates cluster together? – Does similar conditions, time points, tissue types cluster together?
Presentation Using Volcano Plot
Presentation Using Circos Plot
Test Your Hypothesis Without Performing Any Analysis GEO
Test Your Hypothesis Without Performing Any Analysis
Functional Analysis Samples Space n M F Smoking a b c d Suppose in a study, we are trying to find out if the proportion of smoking individual is significantly different between men and women.
Fisher’s Exact Test MaleFemaleTotal Smokingaba + b Nonsmokingcdc + d Totala + cb + da+b+c+d=n H 0 : The proportion of smoking in male == the proportion of smoking in female H 1 : The proportion of smoking in male != the proportion of smoking in female
Fisher’s Exact Test – in Functional Analysis Winner Genes Non Winner Genes Breast Cancer Genes ab Non Brest Cancer Genes cd a b c Breast Cancer Genes Winner Genes All Genes d
Analogy There are Balls: in a box. Blindfolded, you randomly draw 100 balls. What is the probability that you draw less than 50
Gene Set Enrichment Analysis KS test based analysis (Ref)Ref GSEA does not need a winner list first
SNV and Indel Difficulty due to high false positive rate RNAMapper (Miller, et al. Genome Research, 2013) SNVQ (Duitama, et al. (BMC Genomics, 2013) FX (Hong, et al. Bioinformatics, 2012) OSA (Hu, et al. Binformatics, 2012)
Microsatellite instability Examples: Yoon, et al. Genome Research 2013 Zheng, et al. BMC Genomics, 2013
RNA Editing and Allele-specific expression RNA editing tools and database DARNED, REDidb, dbRES, RADAR Allele-specific expression asSeq (Sun, et al. Biometrics, 2012) AlleleSeq (Rozowsky, et al. Molecular Systems Biology, 2011)
Exogenous RNA Virus (Same as DNA) Food RNA (you are what you eat) Wang, et al. PLOS ONE, 2012