the european nutrigenomics organisation deciding and acting on quality of microarray experiments in...
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the European Nutrigenomics Organisation
NuNuGOGONuNuGOGO
Deciding and acting on quality of microarray experiments in genomics
Chris EveloBiGCaT Bioinformatics Maastricht
the European Nutrigenomics Organisation
NuNuGOGONuNuGOGO
The transfer of information from DNA to protein. The transfer proceeds by means of an RNA intermediate called messenger RNA (mRNA). In procaryotic cells the process is simpler than in eucaryotic cells. In eucaryotes the coding regions of the DNA (in the exons,shown in color) are separated by noncoding regions (the introns). As indicated, these introns must be removed by an enzymatically catalyzed RNA-splicing reaction to form the mRNA.
From: Alberts et al. Molecular Biology of the Cell, 3rd edn.
Gene Expression
the European Nutrigenomics Organisation
NuNuGOGONuNuGOGO First Example
Is red wine healthy?
Does it protect rats from eating the unhealthy stuff we usually eat?
the European Nutrigenomics Organisation
NuNuGOGONuNuGOGO
Pool of 10 controls
Cy 3
10 treated
50 mg/kg·day,
2 wks
Cy 5
• Control group:10 male F344 ratsDiet: high fat (23%), high sucrose, low fibre
• Experimental group: 10 male F344 ratsSame diet plus 50 mg/kg red wine polyphenols
Experimental design
DNA MicroarrayDNA Microarray
Rat genomeRat Genome Oligo Set Version 1.1™ (Operon Technologies)
5707 oligos
Omnigrid 100 microarrayer
poly-L-lysine glass slides
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NuNuGOGONuNuGOGO Microarray Principle
The The genomics genomics workflowworkflow
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NuNuGOGONuNuGOGO
Conclusions disagree with previous results– 690 genes regulated genes– Involved in:
cell adhesion and cell-cell communication– Instead of:
e.g. antioxidant activity
Before our analysis
Quality controlQuality control-using Spotfire DecisionSite- (I)-using Spotfire DecisionSite- (I)
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Microarray laser scan.16 Print blocks
Created with Spotfire DecisionSiteColors represent feature numbers of spots on microarray
Quality controlQuality control-using Spotfire DecisionSite- (II)-using Spotfire DecisionSite- (II)
•Localization of the flagged features (empty spots and bad spots (e.g. Signal < BG))
•Flagged features are removed for further analysis
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NuNuGOGONuNuGOGOHierarchical Clustering
7.12E3 0
1 1706 2 2
rat 5 rat 12 rat 14 rat 13 rat 4 rat 3 rat 2 rat 1 rat 15 rat 11
Hierarchical Clustering
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NuNuGOGONuNuGOGO K-means Clustering
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NuNuGOGONuNuGOGO Dissimilar GenesHierarchical Clustering
5 12 14 13 4 3 2 1 15 11
690 genes
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NuNuGOGONuNuGOGO Dissimilar Genes
?Disagreement with biological data
Questions
Differences due to the dietary treatment?Check on the rats growth during the experimental time and on their weight at sacrifice
Differences due to the natural inter-individual variability?Fischer 344 are inbred rats, genetically very similar. A variability among rats is (of course) possible but unlikely in this case, due to the type of treatment and to the large amount of differences observed (more than 600 genes differentially expressed)
Technical problem?
Scatter Plot
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Localization of the differentially expressed genesLocalization of the differentially expressed genes-using Spotfire DecisionSite--using Spotfire DecisionSite-
Scatter Plot
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Scatter Plot
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Log ratio
3.48E3 0
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rat 14 rat 12 rat 5 rat 13 rat 1 rat 11 rat 15 rat 4 rat 3 rat 2
Visualize expression resultsVisualize expression results
SwissProt
Most important results of genMAPP Most important results of genMAPP
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NuNuGOGONuNuGOGO Conclusions
Using Spotfire Decisionsite we can:• see problems on microarrays• see unexpected things
using variable sliders• group co-expressed genes (clustering, pca)• see the location of specific genes or groups of genes• immediately see the effects of alternative
treatments• combine with biological interpretation in
GenMAPP
Example 2: Antibody MicroarrayExample 2: Antibody MicroarrayBD Biosciences (Clontech)BD Biosciences (Clontech)
Chip-based technology Monoclonal antibodies
printed at high density on a glass slide Profiling hundreds of proteins Analyses virtually any biological sample
(cells, whole tissue and body fluids)
Content of antibody arrayContent of antibody array
Two slides with flipped samplesTwo slides with flipped samples
Internally normalized resultsInternally normalized results
Sampling method controls for differences in labeling efficiency
Internally Normalized Ratio can be calculated
(represents the relative abundance of an antigen in sample A relative to that of sample B)
Ratio2
Ratio1
First arrays did not look First arrays did not look good...good...
Array 2
Array 3
Technique improvement...Technique improvement...
Technique improvement...Technique improvement...
Less background problems but also less signal…
Spotfire analysis showed:Spotfire analysis showed:
Technique needs improvements!
Location of the antibodies on the Microarray
Some high background antibodiesProcedure Normalization method
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NuNuGOGONuNuGOGO Participants
BiGCaT Bioinformatics:
• Rachel van Haaften
• Arie van Erk
• Chris Evelo
Florence University
• Christina Luceri
Funding:
• NuGO (exchange)
• NBIC (Spotfire server)