BulkSignalR :
Inference of ligand-receptor interactions from bulk data or spatial transcriptomics

Jean-Philippe Villemin

Institut de Recherche en Cancérologie de Montpellier, Inserm, Montpellier, France
jean-philippe.villemin@inserm.fr

Jacques Colinge

Institut de Recherche en Cancérologie de Montpellier, Inserm, Montpellier, France
jacques.colinge@inserm.fr

01/08/2025

Code
library(BulkSignalR)

Differential mode

BulkSignalR now allows the user to request different pairwise comparisons from a large cohort of samples.

In this mode, ligand-receptor interactions are inferred based on gene or protein regulation-associated P-values when comparing two clusters of samples.

The user must first perform a differential expression analysis (using the tool of his choice as DESeq2, EdgeR…) between a pair of sample clusters.

In the next chunk of code, we describe an application to Salivary Duct Carcinoma (SDC) samples where we compare two clusters of patients.

We first create a BSR-DataModel object as follows :

Code
data(sdc, package = "BulkSignalR")
normal <- grep("^N", names(sdc))
bsrdm <- BSRDataModel(sdc[, -normal])

As an example here, we generate random values but user should provide his own logFC and associated pvalues from DGE ouputs.

Code
colA <- as.integer(1:3)
colB <- as.integer(12:15)

# We then coerce the initial **BSRDataModel** object to 
# a **BSRDataModelComp** object. 

bsrdm.comp <- as(bsrdm, "BSRDataModelComp")


n <- nrow(ncounts(bsrdm.comp))
stats <- data.frame(pval = runif(n),
logFC = rnorm(n, 0, 2),
expr = runif(n, 0, 10))
rownames(stats) <- rownames(ncounts(bsrdm.comp))

We define the cluster comparison and add it.

Code
bsrcc <- BSRClusterComp(bsrdm.comp, colA, colB, stats)
bsrdm.comp <- addClusterComp(bsrdm.comp, bsrcc, "random.example")

Finally we infer ligand-receptor interactions from the comparison. We use a subset of the reference to speed up inference in the context of the vignette.

Code
subset <- c("REACTOME_BASIGIN_INTERACTIONS",
"REACTOME_SYNDECAN_INTERACTIONS",
"REACTOME_ECM_PROTEOGLYCANS",
"REACTOME_CELL_JUNCTION_ORGANIZATION")

reactSubset <- BulkSignalR:::.SignalR$BulkSignalR_Reactome[
BulkSignalR:::.SignalR$BulkSignalR_Reactome$`Reactome name` %in% subset,]

resetPathways(dataframe = reactSubset,
resourceName = "Reactome")

bsrinf.comp <- BSRInferenceComp(bsrdm.comp,
reference="REACTOME",
max.pval = 1, 
"random.example")

head(LRinter(bsrinf.comp))
##          L     R         pw.id                        pw.name       pval
## 6     AGRN  MUSK R-HSA-3000178     REACTOME_ECM_PROTEOGLYCANS 0.18366630
## 25    CALR ITGAV R-HSA-3000170 REACTOME_SYNDECAN_INTERACTIONS 0.02219996
## 251   CALR ITGAV R-HSA-3000178     REACTOME_ECM_PROTEOGLYCANS 0.02190318
## 55  COL4A4 ITGAV R-HSA-3000170 REACTOME_SYNDECAN_INTERACTIONS 0.05377459
## 551 COL4A4 ITGAV R-HSA-3000178     REACTOME_ECM_PROTEOGLYCANS 0.05305570
## 57  COL4A6 ITGAV R-HSA-3000170 REACTOME_SYNDECAN_INTERACTIONS 0.03694712
##           qval  L.logFC  R.logFC    LR.pval LR.corr rank len rank.pval
## 6   0.18837570 1.318274 1.563014 0.40134711       1    9  17 0.4872850
## 25  0.07389423 1.394406 2.348577 0.06956223       1    6  11 0.4310522
## 251 0.07389423 1.394406 2.348577 0.06956223       1   13  24 0.4310522
## 55  0.08280531 2.891966 2.348577 0.16849939       1    6  11 0.4310522
## 551 0.08280531 2.891966 2.348577 0.16849939       1   13  24 0.4310522
## 57  0.07389423 1.452941 2.348577 0.11577154       1    6  11 0.4310522
##     rank.corr  LR.score   L.expr   R.expr
## 6           1 0.1859113 9.412899 3.334787
## 25          1 0.1852940 4.295503 6.728237
## 251         1 0.1852940 4.295503 6.728237
## 55          1 0.1753966 3.296953 6.728237
## 551         1 0.1753966 3.296953 6.728237
## 57          1 0.2063148 7.823487 6.728237

Technical notes

Three previously described S4 objects (BSR-DataModel, BSR-Inference, BSR-Signature) have been extented :


A new S4 object BSR-ClusterComp representing the comparison of two clusters of samples to infer LR interactions based on the resulting P-values and log-fold-changes (logFC) has been added.

This new desgin let us handle sample cluster comparisons.

as.BSRDataModelComp converts of BSR-DataModel into BSR-DataModelComp In case ligand-receptor inferences should be obtained based on gene/protein regulation P-values comparing two clusters of samples, it is necessary to first promote the BSR-DataModel object that contains the count matrix into a BSR-DataModelComp object able to contain a list of such cluster pairs comparisons. This function performs this promotion, adding an empty list of comparisons.

BSRClusterComp is used to define the comparison between two clusters of samples by using defined column indexes of the expression matrix that belong to each cluster, and storing the result of the cluster difference statistical analysis obtained by an external tool such as edgeR, DESeq2, etc.

addClusterComp add a comparison between two clusters of samples to a BSR-DataModelComp object.

Several comparison can be defined and added sequentially.


Thank you for reading this guide and for using BulkSignalR.

Session Information

Code
sessionInfo()
## R Under development (unstable) (2024-10-21 r87258)
## Platform: x86_64-pc-linux-gnu
## Running under: Ubuntu 24.04.1 LTS
## 
## Matrix products: default
## BLAS:   /home/biocbuild/bbs-3.21-bioc/R/lib/libRblas.so 
## LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.12.0
## 
## locale:
##  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
##  [3] LC_TIME=en_GB              LC_COLLATE=C              
##  [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
##  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
##  [9] LC_ADDRESS=C               LC_TELEPHONE=C            
## [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       
## 
## time zone: America/New_York
## tzcode source: system (glibc)
## 
## attached base packages:
## [1] stats     graphics  grDevices utils     datasets  methods   base     
## 
## other attached packages:
## [1] BulkSignalR_0.99.22
## 
## loaded via a namespace (and not attached):
##   [1] DBI_1.2.3                   grr_0.9.5                  
##   [3] gridExtra_2.3               rlang_1.1.4                
##   [5] magrittr_2.0.3              clue_0.3-66                
##   [7] GetoptLong_1.0.5            matrixStats_1.5.0          
##   [9] compiler_4.5.0              RSQLite_2.3.9              
##  [11] gprofiler2_0.2.3            png_0.1-8                  
##  [13] vctrs_0.6.5                 ggalluvial_0.12.5          
##  [15] pkgconfig_2.0.3             SpatialExperiment_1.17.0   
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## [103] homologene_1.4.68.19.3.27   Formula_1.2-5              
## [105] cli_3.6.3                   viridisLite_0.4.2          
## [107] S4Arrays_1.7.1              ComplexHeatmap_2.23.0      
## [109] dplyr_1.1.4                 gtable_0.3.6               
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## [121] farver_2.1.2                rjson_0.2.23               
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## [125] multtest_2.63.0             lifecycle_1.0.4            
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## [129] bit64_4.5.2                 MASS_7.3-64