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What is the meaning of 'intercept' in the deseq2 results?

I have a dataset associated with two factors(Stage and Form). Stage has 4 conditions and Form has two conditions:

          Stage  Form
DS1_Wr60  Wr60   DS
DS2_Wr60  Wr60   DS
DS3_Wr60  Wr60   DS
DS4_Wr60  Wr60   DS
WS1_Wr60  Wr60   WS
WS2_Wr60  Wr60   WS
WS3_Wr60  Wr60   WS
WS4_Wr60  Wr60   WS
DS1_PP50  PP50   DS
DS2_PP50  PP50   DS
DS3_PP50  PP50   DS
DS4_PP50  PP50   DS
WS1_PP50  PP50   WS
WS2_PP50  PP50   WS
WS3_PP50  PP50   WS
WS4_PP50  PP50   WS
DS1_P15    P15   DS
DS2_P15    P15   DS
DS3_P15    P15   DS
DS4_P15    P15   DS
WS1_P15    P15   WS
WS2_P15    P15   WS
WS3_P15    P15   WS
WS4_P15    P15   WS
DS1_P50    P50   DS
DS2_P50    P50   DS
DS3_P50    P50   DS
DS4_P50    P50   DS
WS1_P50    P50   WS
WS2_P50    P50   WS
WS3_P50    P50   WS
WS4_P50    P50   WS

I performed deseq2 analysis like this:

col_data <- data.frame(row.names = colnames(count_data),Stage,Form)
dds <- DESeqDataSetFromMatrix(countData = count_data,colData = col_data,design = ~ Stage+Form)
> dds_out <- DESeq(dds_filter)
estimating size factors
estimating dispersions
gene-wise dispersion estimates
mean-dispersion relationship
final dispersion estimates
fitting model and testing
> resultsNames(dds_out)
[1] "Intercept"         "Stage_P50_vs_P15"  "Stage_PP50_vs_P15" "Stage_Wr60_vs_P15" "Form_WS_vs_DS"

I understand the other comparisons made but what about the "Intercept"? What does it indicate?

rna-seq rna-seq r deseq2

1 answer

It's the baseline expression of each gene.

Hi, thank you for your reply. Could you elaborate more in the context of my specific case? When I look into the intercept result it still shows some genes up and down...What does it mean?

What do you mean by "up and down"?

I mean genes are up- or down-regulated in the intercept result. How can I interpret this? What comparison did it make?

> res <- results(dds_out,name = "Intercept")
> summary(res)
out of 19287 with nonzero total read count
adjusted p-value < 0.1
LFC > 0 (up)       : 13119, 68%
LFC < 0 (down)     : 461, 2.4%
outliers [1]       : 161, 0.83%
low counts [2]     : 0, 0%
(mean count < 0)
[1] see 'cooksCutoff' argument of ?results
[2] see 'independentFiltering' argument of ?results

I'm not sure but I think that the null hypothesis is that the baseline expression is 0 so every expressed gene will be significantly up, not sure about the down, perhaps it's a normalization artifact.

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