Question: Help with limma contrast/design matrices
gravatar for mat149
3.0 years ago by
mat14940 wrote:


I was hoping someone could give this script a look-through and determine if I have made an error at some point.  This regards the analysis of Affymetrix 1.1 st zebrafish gene arrays.

I have three groups of samples and I am detecting differentially expressed genes between all three contrasts (1: morphant-control 2: rescue-control 3: morphant-rescue).  I have 8x control samples, 4x treatment#1 (morphant) samples, and 4x treatment#2 (rescue) samples.  I am using limma's lmFit and eBayes for this.  When I get my topTable results back, the fold change signs are inverted. The genes that should be downregulated are returned as positive logFC integers and vice versa . I know from analyzing this data previously that, for instance, KEGG pathway enrichment for phototransduction should be downregulated but in this case it will be returned as upregulated.

It seems like a silly inquiry, but I cant figure it out.



#### read samples in

CELlist <- list.celfiles("C:\\Users\\mat149\\Desktop\\GG\\CEL", full.names=TRUE, pattern=NULL, all.file=FALSE)
CELdat <- read.celfiles(filenames = CELlist,experimentData=TRUE,phenoData=pdat,verbose=TRUE)

### RMA

eset<-rma(CELdat, background=TRUE, normalize=TRUE, subset=NULL, target="core")     
eset <- annotateEset(eset, annotation(eset))

fd <- fData(eset)
fd$ENTREZID <- mapIds(, as.character(fd$SYMBOL), "ENTREZID","SYMBOL")
fData(eset) <- fd




ph = CELdat@phenoData 
ph@data[ ,1] = c("WT1","WT2","WT3","WT4","WT5","WT6","WT7","WT8","MO1","MO2","MO3","MO4","RS1","RS2","RS3","RS4")
ph@data[ ,2] = c("control","control","control","control","control","control","control","control","morphant","morphant","morphant","morphant","rescue","rescue","rescue","rescue")
groups = ph@data$Treatment
f = factor(groups,levels=c("control","morphant","rescue"))


#### LIMMA

design = model.matrix(~ 0 + f)
design = lmFit(eset,design)

contrast.matrix = makeContrasts(morphant-control,rescue-control,morphant-rescue,levels=design) =,contrast.matrix) = eBayes(





> sessionInfo()
R version 3.3.1 (2016-06-21)
Platform: i386-w64-mingw32/i386 (32-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] stats4    parallel  stats     graphics  grDevices utils     datasets 
[8] methods   base     

other attached packages:
 [1] limma_3.28.21         AnnotationDbi_1.34.4    
 [4] affycoretools_1.44.3     pd.zebgene.1.1.st_3.12.0 RSQLite_1.0.0           
 [7] DBI_0.5-1                oligo_1.36.1             Biostrings_2.40.2       
[10] XVector_0.12.1           IRanges_2.6.1            S4Vectors_0.10.3        
[13] Biobase_2.32.0           oligoClasses_1.34.0      BiocGenerics_0.18.0     

loaded via a namespace (and not attached):
 [1] httr_1.2.1                    munsell_0.4.3                
 [3] latticeExtra_0.6-28           BSgenome_1.40.1              
 [5] dichromat_2.0-0               R.utils_2.5.0                
 [7] PFAM.db_3.3.0                 httpuv_1.3.3                 
 [9] R6_2.2.0                      ensembldb_1.4.7              
[11] graph_1.50.0                  affxparser_1.44.0            
[13] BiocInstaller_1.22.3          data.table_1.9.6             
[15] reshape_0.8.6                 annotate_1.50.1              
[17] xtable_1.8-2                  gdata_2.17.0                 
[19] tools_3.3.1                   stringr_1.1.0                
[21] rtracklayer_1.32.2            mime_0.5                     
[23] GSEABase_1.34.1               shiny_0.14.2                 
[25] chron_2.3-47                  R.oo_1.21.0                  
[27] GOstats_2.38.1                foreach_1.4.3                
[29] digest_0.6.10                 KernSmooth_2.23-15           
[31] GO.db_3.3.0                   GenomeInfoDb_1.8.7           
[33] codetools_0.2-15              GGally_1.2.0                 
[35] ff_2.2-13                     GenomicAlignments_1.8.4      
[37] gplots_3.0.1                  genefilter_1.54.2            
[39] scales_0.4.1                  stringi_1.1.2                
[41] locfit_1.5-9.1                R.methodsS3_1.7.1            
[43] gcrma_2.44.0                  lattice_0.20-33              
[45] AnnotationForge_1.14.2        interactiveDisplayBase_1.10.3
[47] biovizBase_1.20.0             Rcpp_0.12.7                  
[49] OrganismDbi_1.14.1            caTools_1.17.1               
[51] Hmisc_4.0-0                   Formula_1.2-1                
[53] ggplot2_2.1.0                 htmlTable_1.7                
[55] Category_2.38.0               grid_3.3.1                   
[57] ReportingTools_2.12.2         GenomicRanges_1.24.3         
[59] preprocessCore_1.34.0         plyr_1.8.4                   
[61] RBGL_1.48.1                   survival_2.39-4              
[63] edgeR_3.14.0                  acepack_1.4.1                
[65] affy_1.50.0                   rpart_4.1-10                 
[67] magrittr_1.5                  SummarizedExperiment_1.2.3   
[69] VariantAnnotation_1.18.7      gridExtra_2.2.1              
[71] affyio_1.42.0                 biomaRt_2.28.0               
[73] htmltools_0.3.5               ggbio_1.20.2                 
[75] knitr_1.15                    nnet_7.3-12                  
[77] gtable_0.2.0                  zlibbioc_1.18.0              
[79] colorspace_1.2-7              geneplotter_1.50.0           
[81] cluster_2.0.4                 gtools_3.5.0                 
[83] RCurl_1.95-4.8                DESeq2_1.12.4                
[85] bitops_1.0-6                  RColorBrewer_1.1-2           
[87] Matrix_1.2-6                  foreign_0.8-66               
[89] bit_1.1-12                    GenomicFeatures_1.24.5       
[91] hwriter_1.3.2                 reshape2_1.4.2               
[93] XML_3.98-1.4                  AnnotationHub_2.4.2          
[95] iterators_1.0.8               splines_3.3.1                
[97] BiocParallel_1.6.6            Rsamtools_1.24.0

limma contrast matrix • 435 views
ADD COMMENTlink written 3.0 years ago by mat14940

Several points:

  1. Make a limma tag, otherwise the maintainers don't get notified.
  2. Post a specific example of a gene that's behaving in the unexpected manner that you describe, i.e., its expression values across all samples and the log-fold changes that are reported by limma. The code looks (mostly) fine so, right now, there's only your word that something's amiss.
ADD REPLYlink written 3.0 years ago by Aaron Lun25k

In addition: take a gene that "you know" the sign is inverted for and plot its expression from your data among the two groups implicated in your contrast.

I agree with Aaron in that your code looks mostly correct, so apart from perhaps a mislabelling of the conditions to samples, positive logFCs in your coef=1 result will give you genes higher expressed in "morphant" compared to their expression levels in "control"

ADD REPLYlink modified 3.0 years ago • written 3.0 years ago by Steve Lianoglou12k
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