number of grouping affect log2 fold change in DESeq2 analysis?

Question

[star]

I have RNA-seq data for samples in 10 different groups and I would like to find deferentially expressed genes. I have used Deseq2 R package. The deferentially expressed genes have FDR between 0.03 and 0.05. I checked log2FC and found it is low value in most deferentially expressed genes. How I can explain this? Why genes with low log2FC are found to be deferentially expressed? Also I have checked the normalized count and I couldn't find any reason!

[vivekbhr]

How come no differentially expressed gene has fdr below 0.03? I guess you have some kind of filtering going on ..

Answer 1

[Devon Ryan]

The number of groups you're using suggests that there's a lot of variance shrinkage going on, which is why you're picking up low fold-change differences. My guess is that you have relatively few replicates per group, which is causing aggressive fold-change shrinkage.