Question: single cell RNA seq Differential Expression using MAST
gravatar for quintanamaster
9 months ago by
United Kingdom
quintanamaster0 wrote:

Hi all,

I'm using MAST package to detect differentially expressed genes in single cell RNAseq datasets. I've used DESeq2 in the past and I know that it selects the reference group for calculating fold changes alphabetically if not pre-defined. I'm struggling to understand if MAST does the same thing? Does it select the reference group for FC calculation alphabetically? It's not very clear from the documentation available.

Thanks in advance for helping,


sequencing rna-seq next-gen • 668 views
ADD COMMENTlink modified 9 months ago by ATpoint44k • written 9 months ago by quintanamaster0
gravatar for ATpoint
9 months ago by
ATpoint44k wrote:

I guess so. The keyword you are looking for is reference level, see

The relevel function is what you need as described in the first few lines of code of paragraph 4.

ADD COMMENTlink modified 9 months ago • written 9 months ago by ATpoint44k

Thanks ATpoint!

I'm running the code from the Seurat vignette as below:

head<- FindMarkers(Combined, ident.1 = "Ast_2", ident.2 = NULL, test.use = "MAST") View(head) write.csv(head, "../Desktop/Hyp_DE_Ast22.csv", row.names = TRUE)

It doesn't let me use the "relevel" option so that's why I was wondering if it does the selection alphabetically by default?

ADD REPLYlink written 9 months ago by quintanamaster0

It looks like you are actually using Seurat, not MAST. Although you are using the MAST test, you are using Seurat's interface, not the native MAST one. Thus, you have to refer to Seurat documentation.

If you are not sure what the order is, check the average expression (AverageExpression()) and then you can see which group is higher or lower.

ADD REPLYlink written 9 months ago by igor12k
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