Controversial DESEQ2 results
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Stephan • 0
@406a168a
Last seen 22 months ago
Germany

Dear all, I ran a DESEQ2 script to evaluate gene ratio changes. When I have a look on the raw data it seems that the ratio is higher in the PET14 samples when in the Soil/ NoMP controls. But thr Deseq analysis shows me a positive log2fold change for otu 2 which corresponds in a lower ratio in my case. Does anyone have an explanation for this?

Thanks a lot Stephan Below are the original data


T14NoMP1   T14NoMP2   T14NoMP3   T14NoMP4    T14NoMP5       T14PE1      T14PE2       T14PE3       T14PE4       T14PE5    T14Soil1    T14Soil2    T14Soil3    T14Soil4     T14Soil5
otu001 15.49600219 0.71672122 1.04939165 7.25112383 12.41321836 4.235161e-01 20.60396068  5.080065432 15.990734851 20.145296115  0.31653702  0.55708149  0.92024388  6.41080776 23.406969736
otu002  1.71866085 2.43154776 2.02328512 1.90285255  1.76140920 2.153202e+00  2.00962395  3.776349930  2.463601552  2.107220045  0.94157150  1.21138013  1.38092935  1.13129426  1.098722348
otu003  0.04139551 0.02164607 0.01839983 0.02538947  0.02674946 9.308081e-05  0.00458436  0.006081188  0.007444051  0.002374211  0.00717658  0.01013808  0.00558299  0.00509914  0.004146075
otu004  0.33576741 0.50464516 0.40462458 0.32373456  0.34749654 8.001034e-01  0.08304846  0.064430695  0.096548372  0.123210245  0.42297635  0.25579105  0.19918321  0.32468280  0.235927196
otu005  4.77548214 3.29980457 2.59519889 7.42613315  3.54733314 3.703788e+01 52.07337724 36.632964717 18.614310414 40.830865803 39.61681424 15.55572315 31.69627507 16.42143724 18.240599756
otu006  1.14832861 1.25183746 1.14993670 1.33360559  1.07910937 8.022288e-01  3.60871444  3.704028002  2.365334311  2.730540930  0.57839931  1.33972200  1.60898705  1.00387325  1.287353742

 diagdds = phyloseq_to_deseq2(psPE_T14, ~ Polymer)
 calculate geometric means prior to estimate size factors
gm_mean = function(x, na.rm=TRUE){
  exp(sum(log(x[x > 0]), na.rm=na.rm) / length(x))
}
geoMeans = apply(counts(diagdds), 1, gm_mean)
diagdds = estimateSizeFactors(diagdds, geoMeans = geoMeans)
diagdds = DESeq(diagdds, fitType="mean")
res<-results(diagdds)
res

baseMean log2FoldChange     lfcSE       stat    pvalue      padj
       <numeric>      <numeric> <numeric>  <numeric> <numeric> <numeric>
otu001  7.285483      0.4001557  0.837073  0.4780415  0.632621  0.925354
otu002  1.891746      0.6738062  0.766467  0.8791071  0.379343  0.925354
otu003  0.000000             NA        NA         NA        NA        NA
otu004  0.162719      1.0391874  1.371087  0.7579296  0.448493  0.925354
otu005 19.543096     -0.0685950  0.634957 -0.1080309  0.913971  0.925354
otu006  1.474963      0.0734311  0.783753  0.0936916  0.925354  0.925354
phyloseq DESeq2 • 858 views
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Sorry the code and data has to bad format to be understood correctly but are you talking about normalized data ? Because you should never interpret raw counts Have you checked what is your reference when you performed differential analysis ? (this is very important)

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Excuse me for the formatting, it was displayed correctly in the preview but not after submitting. Thanks for improving the format!

Regarding your comment, the reference are the NoMP_T14 and Soil_T14 samples. The data are not normalized, because the values are gene ratios. So we want to check if the gene ratios are different between treatment and control, Its just surprising, since for every other treatment the DESEQ analysis correlates with the ratio changes, but not for this one and I could not find any errors.

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@mikelove
Last seen 1 day ago
United States

Note that I don't recommend use of DESeq2 for microbiome / metagenomics data. It's not clear to me that the assumptions are satisfied.

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