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Whole genome transcriptome variation in Arabidopsis thaliana Xu Zhang Borevitz Lab Whole genome transcriptome variation in Arabidopsis thaliana Xu Zhang Borevitz Lab
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Arabidopsis thaliana have been adapted to highly variable environments
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Transcription and splicing Chromosomal DNA Transcription Nuclear RNA Exon 1 Exon 2 Exon 3 Intron 1Intron 2 RNA splicing Messenger RNA Exon 1Exon 2Exon 3Exon 1Exon 3
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Whole genome tiling array Genetic hybridization polymorphisms could affect the estimation of gene expression High density and resolution: 1.6M unique probes at 35bp spacing Without bias toward known transcripts
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Col♀ x Col♂Van ♀ x Van ♂Col ♀ x Van ♂Van ♀ x Col ♂ parental strains and reciprocal F1 hybrids mRNA from total RNA; genomic DNA The experiment
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Double-stranded random labeling Random reverse transcription Double-stranded cDNA Random priming AAAAA
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Sequence polymorphisms Gene expression variation Splicing variation A functional network of differentially spliced genes HMM for a de novo transcription profiling Outlines
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Sequence polymorphisms Gene expression variation Splicing variation A functional network of differentially spliced genes HMM for a de novo transcription profiling Outlines
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SFP deletion or duplication in Van Single Feature Polymorphisms and indels SFPs SFP
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Sequence polymorphisms SPFs and indels (>200bp) were removed before gene expression analysis SFPs a FDRCol > Van c Van > Col c Total 11.82%13576914934150703 7.66%1264439479135922 5.22%1183816662125043 3.88%1108614979115840 3.15%1041153820107935 Indels b Model selectiondeletionduplicationTotal BIC d 51822540 AIC e 16451361781
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Deletions vs duplications
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Distribution of indels along chromosomes
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Sequence polymorphisms Gene expression variation Splicing variation A functional network of differentially spliced genes HMM for a de novo transcription profiling Outlines
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Additive, dominant and maternal effects of gene expression
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The linear model Gene probe Intensity ~ additive + dominant + maternal + ε intensity Col Van F1c F1v additive maternal dominant genotypes
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Gene expression variation between genotypes Delta a Sig+ b Sig- c TotalFalse d FDR additive 0.549113967887890110.15% 12674173644102154.88% 1.516269232549702.76% 1.812496761925392.03% 2.56903341024131.24% dominant 0.515113190470176716.31% 1405152119261869.65% 1.5157811968676.93% 1.892575667405.99% 2.541270311144.65% maternal 0.5599895609373512.06% 12046820541517.37% 1.54800 4910.29% 1.81630 2817.33% 2.5410 922.84%
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Mean gene intensity Van dominant Col dominant over dominant F1v dominantF1c dominant Maternal paternal The pattern of gene expression inheritance Col Van F1v F1c
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The pattern of gene expression inheritance
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Enrichment in GO functional categories GO enrichment for additive dominant maternal effect genes Defense response genes are highly expressed in F1 hybrid lines, while many growth related pathway are down-regulated
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Sequence polymorphisms Gene expression variation Splicing variation A functional network of differentially spliced genes HMM for a de novo transcription profiling Outlines
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Default expression status of exon and intron Exons: correction for gene expression corrected by gene mean corrected by a gene median splicing index (Mean exon /Mean gene ) Introns: direct comparison Exon/intron probe Intensity ~ additive + dominant + maternal + ε
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Differential exon splicing Exon probe Intensity ~ additive + dominant + maternal + ε Delta a Sig+ b Sig- c TotalFalse d FDR corrected by gene mean 0.3287190477559117% 0.417712930620567.0% 0.51271092369741.0% 0.692861785530.8% 0.777691463423.4% Corrected by gene median 0.352328080355669.2% 0.432817250020340.6% 0.52231203439628.0% 0.6154762305423.5% 0.7123521753419.3% Splicing index 0.340723564242566.0% 0.429217546713228.0% 0.52301433735013.0% 0.6178104282217.50% 0.714886234104.30%
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Differential intron splicing Intron probe Intensity ~ additive + dominant + maternal + ε Delta a Sig+ b Sig- c TotalFalse d FDR 0.35611034159533220.8% 0.4405523928859.17% 0.5316352668284.26% 0.6239220459122.61% 0.720215535771.91% 0.817612029651.53%
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Differential exon splicing is predominantly additive in F1 hybrids
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Some dominant effect in differential intron splicing in F1 hybrids
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Comparison for enrichment in known alternatively spliced exons Threshold 1Threshold 2 CalledNot calledCalledNot called Corrected by gene mean Known 2899171012 Not known 397551459055452 Fold enrichment 3.924.26 p-value 5.97E-091.90E-03 Corrected by gene median polish Known 2499561013 Not known 430551128555457 Fold enrichment 3.093.86 p-value 3.60E-066.14E-03 Splicing index Known 24109351112 Not known 537723288872777 Fold enrichment 2.963.72 p-value 6.84E-061.36E-02
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AT1G21350 AT1G34180 AT1G76170 AT1G29120 AT1G51350 AT1G80960 AT1G07350 Experimental determined FDR for differential splicing # of significant calls estimated FDR # of tested # of confirmed experimental FDR Exon (corrected by mean) 477117%452251.1% 11120.8%181044.4% Exon (corrected by median) 50040.6%402147.5% 10315.60%171041.2% Exon (splicing index) 64266.0%502354.0% 1021.00%201050.0% intron 4592.61%653841.5% 1951.15%583343.1%
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Sequence polymorphisms Gene expression variation Splicing variation A functional network of differentially spliced genes HMM for a de novo transcription profiling Outlines
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Enrichment of differentially spliced genes in chloroplast thylakoid enrichment of differentially spliced genes
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Chloroplast thylakoid
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Differrentially spliced genes which are located in chloroplast thylakoid Photosynthesis related genes AT5G38660 APE1 (Acclimation of Photosynthesis to Environment) mutant has altered acclimation responses
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AT1G07350transformer serine/arginine-richribonucleoprotein putative AT1G55310SC35-like splicing factor 33 kD(SCL33) AT2G29210splicing factor PWIdomain-containing protein AT5G04430KH domain-containing proteinNOVA putative Splicing regulator tend to be differentially spliced
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Sequence polymorphisms Gene expression variation Splicing variation A functional network of differentially spliced genes HMM for a de novo transcription profiling Outlines
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Generalized tiling array HMM 3-state HMM Discrete distribution for emission probability Transition probability counts for probe spacing Baum-Welch parameter estimation (by Jake Byrnes)
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An example of HMM detected segments
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A nice model also needs better array Array density is not enough to distinguish exon/intron boundaries Probe quality
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Differential segments >=3 continuous probes with posterior probability >0.99. Differentially expressed genes annotated genes for which ≥33% of their probes reside within the observed differential segments. Differentially spliced genes annotated genes for which <33% of probes resided within the differential segment, or annotated genes containing ≥2 differential segments with different states. Novel gene boundaries differential segments with >= 5 probes extending beyond annotated gene boundary Novel transcripts differential segments with >= 5 probes and outside any annotated gene boundary.
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Length distribution of segments called by HMM
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Comparison of annotation-based analysis and HMM Col > VanVan > ColTotal Annotation differential expression a 16269232549 differential exonic splicing b 287190477 differential intronic splicing c 202155357 HMM differential expression d 16549622616 differential splicing e 8745301404 un-annotated transcript f 344276 un-annotated 5' g 301949 un-annotated 3' g 28836
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Comparison of annotation-based analysis and HMM Annotation Expression (Col>Van) Expression (Van>Col) Splicing (Col>Van) Splicing (Van>Col) HMM 1654962921550 Expression (Col>Van) 16261270 225 Expression (Van>Col) 923 727132 Splicing (Col>Van) 44118147 Splicing (Van>Col) 300 9038
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Acknowledgements Justin Borevitz Yan Li Christos Noutsos Geoff Morris Andy Cal Jake Byrnes Josh Rest
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