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Bioinformatics for Stem Cell Lecture 2 Debashis Sahoo, PhD
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Outline Lecture 1 Recap Multivariate analysis Microarray data analysis Boolean analysis Sequencing data analysis
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MULTIVARIATE ANALYSIS
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Identify Markers of Human Colon Cancer and Normal Colon 4 Piero DalerbaTomer Kalisky
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Single Cell Analysis of Normal Human Colon Epithelium
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Hierarchical Clustering
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Cluster 3.0 – http://bonsai.hgc.jp/~mdehoon/software/cluster/ http://bonsai.hgc.jp/~mdehoon/software/cluster/ Distance metric – Euclidian, Squared Euclidean, Manhattan, maximum, cosine, Pearson’s correlation Linkage – Single, complete, average, median, centroid
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Multivariate Analysis - PCA X = data matrix V = loading matrix U = scores matrix Principal Component Analysis
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Fundamentals of PCA Reduces dimensions of the data PCA uses orthogonal linear transformation First principal component has the largest possible variance. Exploratory tool to uncover unknown trends in the data
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PCA Analysis
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HIGH-THROUGHPUT DATA ANALYSIS
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MICROARRAY ANALYSIS
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Microarray Spotted vs. in situ Two channel vs. one channel Probe vs. probeset vs. gene
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Quantile Normalization Sort Average #1#2#3 Val(Probe_i) = SortedAvg[Rank(Probe_i)] SortedAvg
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Invariant Set Normalization Before Normalization After Normalization Invariant set
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Good to Check the Image
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1.Assign experiments to two groups, e.g., in the expression matrix below, assign Experiments 1, 2 and 5 to group A, and experiments 3, 4 and 6 to group B. Exp 1Exp 2Exp 3Exp 4Exp 5Exp 6 Gene 1 Gene 2 Gene 3 Gene 4 Gene 5 Gene 6 2. Question: Is mean expression level of a gene in group A significantly different from mean expression level in group B? Exp 1Exp 2Exp 3Exp 4Exp 5Exp 6 Gene 1 Gene 2 Gene 3 Gene 4 Gene 5 Gene 6 Group AGroup B SAM Two-Class Unpaired
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Permutation tests i)For each gene, compute d-value (analogous to t-statistic). This is the observed d-value for that gene. ii) Rank the genes in ascending order of their d-values. iii) Randomly shuffle the values of the genes between groups A and B, such that the reshuffled groups A and B respectively have the same number of elements as the original groups A and B. Compute the d-value for each randomized gene Exp 1Exp 2Exp 3Exp 4Exp 5Exp 6 Gene 1 Group AGroup B Exp 1Exp 4Exp 5Exp 2Exp 3Exp 6 Gene 1 Group AGroup B Original grouping Randomized grouping SAM Two-Class Unpaired
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iv) Rank the permuted d-values of the genes in ascending order v) Repeat steps iii) and iv) many times, so that each gene has many randomized d-values corresponding to its rank from the observed (unpermuted) d-value. Take the average of the randomized d-values for each gene. This is the expected d-value of that gene. vi) Plot the observed d-values vs. the expected d-values
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SAM Two-Class Unpaired Significant positive genes (i.e., mean expression of group B > mean expression of group A) Significant negative genes (i.e., mean expression of group A > mean expression of group B) “Observed d = expected d” line The more a gene deviates from the “observed = expected” line, the more likely it is to be significant. Any gene beyond the first gene in the +ve or –ve direction on the x-axis (including the first gene), whose observed exceeds the expected by at least delta, is considered significant.
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GenePattern http://genepattern.broadinstitute.org/
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AutoSOME http://jimcooperlab.mcdb.ucsb.edu/autosome/ Aaron Newman and James Cooper, BMC Bioinformatics, 2010, 11:117 Aaron Newman
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Gene Set Analysis Cell Cycle Transcription factor TGF-beta Signaling Pathway Wnt-signaling Pathway Protein-protein interaction network Your Gene Set Compute enrichment in pathways and networks Tools: GSEA, DAVID, Toppfun, MSigDB, and STRING
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BOOLEAN ANALYSIS
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Boolean Implication Analyze pairs of genes. Analyze the four different quadrants. Identify sparse quadrants. Record the Boolean relationships. – If ACPP high, then GABRB1 low – If GABRB1 high, then ACPP low ACPP GABRB1 [Sahoo et al. Genome Biology 08] 45,000 Affymetrix microarrays
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Threshold Calculation A threshold is determined for each gene. The arrays are sorted by gene expression StepMiner is used to determine the threshold Sorted arrays CDH expression [Sahoo et al. 07] Threshold High Low Intermediate
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BooleanNet Statistics [Sahoo et al. Genome Biology 08] nA low = (a 00 + a 01 ), nB low = (a 00 + a 10 ) total = a 00 + a 01 + a 10 + a 11, observed = a 00 expected = (nA low / total * nB low / total) * total a 00 (a 00 + a 01 ) a 00 (a 00 + a 10 ) + () 1 2 error rate = a 00 a 01 a 11 a 10 A B statistic = (expected – observed) expected √ Boolean Implication = (statistic > 3, error rate < 0.1)
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Six Boolean Implications [Sahoo et al. Genome Biology 08]
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MiDReG Algorithm [Sahoo et al. PNAS 2010] MiDReG = (Mining Developmentally Regulated Genes)
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MiDReG Algorithm [Sahoo et al. PNAS 2010] MiDReG = (Mining Developmentally Regulated Genes)
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MiDReG Algorithm [Sahoo et al. PNAS 2010] MiDReG = (Mining Developmentally Regulated Genes)
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B Cell Genes [Sahoo et al. PNAS 2010] CD19 KIT Boolean Implications
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Jun Seita [Seita, Sahoo et al. PLoS ONE, 2012] http://gexc.stanford.edu
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SEQUENCING DATA ANALYSIS
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Sequencing Data Format @HWI-EAS209:5:58:5894:21141#ATCACG/1 TTAATTGGTAAATAAATCTCCTAATAGCTTAGATNT +HWI-EAS209:5:58:5894:21141#ATCACG/1 efcfffffcfeefffcffffffddf`feed]`]_Ba >SEQUENCE_1 MTEITAAMVKELRESTGAGMMDCKNALSETNGDFDKAVQLLREKGLGKAAKKADRLAAEG LVSVKVSDDFTIAAMRPSYLSYEDLDMTFVENEYKALVAELEKENEERRRLKDPNKPEHK IPQFASRKQLSDAILKEAEEKIKEELKAQGKPEKIWDNIIPGKMNSFIADNSQLDSKLTL MGQFYVMDDKKTVEQVIAEKEKEFGGKIKIVEFICFEVGEGLEKKTEDFAAEVAAQL >SEQUENCE_2 SATVSEINSETDFVAKNDQFIALTKDTTAHIQSNSLQSVEELHSSTINGVKFEEYLKSQI ATIGENLVVRRFATLKAGANGVVNGYIHTNGRVGVVIAAACDSAEVASKSRDLLRQICMH FASTA FASTQ S - Sanger Phred+33, (0, 40) X - Solexa Solexa+64,(-5, 40) I - Illumina 1.3+ Phred+64, (0, 40) J - Illumina 1.5+ Phred+64, (3, 40) L - Illumina 1.8+ Phred+33, (0, 41)
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Mapping
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Mapping Software Long reads – BLAST, HMMER, SSEARCH Short reads – BLAT – Bowtie, BWA, Partek, SOAP, Tophat, Olego, BarraCUDA
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Visualizations
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UCSC Genome Browser GenoViewer, Samtools tview, MaqView, rtracklayer, BamView, gbrowse2 Integrative Genomics Viewer (IGV)
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Quantification Peak calling – QuEST, MACS, PeakSeq, T-PIC, SIPeS, GLITR, SICER, SiSSRs, OMT Expression quantification – Cufflinks, NEUMA, RSEM, ABySS, ERANGE, RSAT, Velvet, MISO, RSEQ SNP calling – samtools, VarScan, GATK, SOAP2, realSFS, Beagle, QCall, MaCH
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Peak Discovery [Pepke et al. Nature Methods 2009]
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Transcript Quantification [Pepke et al. Nature Methods 2009] RPKM, FPKM
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SNP Calling
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Typical RNA-seq Workflow [Trapnell et al. Nature Biotech 2010]
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