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Load and process single cell data

Here we perform analysis of PBMCs from 8 individuals stimulated with interferon-β Kang, et al, 2018, Nature Biotech. We perform standard processing with dreamlet to compute pseudobulk before applying crumblr.

Here, single cell RNA-seq data is downloaded from ExperimentHub.

library(dreamlet)
library(muscat)
library(ExperimentHub)
library(scater)

# Download data, specifying EH2259 for the Kang, et al study
eh <- ExperimentHub()
sce <- eh[["EH2259"]]

sce$ind <- as.character(sce$ind)

# only keep singlet cells with sufficient reads
sce <- sce[rowSums(counts(sce) > 0) > 0, ]
sce <- sce[, colData(sce)$multiplets == "singlet"]

# compute QC metrics
qc <- perCellQCMetrics(sce)

# remove cells with few or many detected genes
ol <- isOutlier(metric = qc$detected, nmads = 2, log = TRUE)
sce <- sce[, !ol]

# set variable indicating stimulated (stim) or control (ctrl)
sce$StimStatus <- sce$stim

Aggregate to pseudobulk

Dreamlet creates the pseudobulk dataset:

# Since 'ind' is the individual and 'StimStatus' is the stimulus status,
# create unique identifier for each sample
sce$id <- paste0(sce$StimStatus, sce$ind)

# Create pseudobulk data by specifying cluster_id and sample_id for aggregating cells
pb <- aggregateToPseudoBulk(sce,
  assay = "counts",
  cluster_id = "cell",
  sample_id = "id",
  verbose = FALSE
)

Process data

Here we evaluate whether the observed cell proportions change in response to interferon-β.

library(crumblr)

# use dreamlet::cellCounts() to extract data
cellCounts(pb)[1:3, 1:3]
##          B cells CD14+ Monocytes CD4 T cells
## ctrl101      101             136         288
## ctrl1015     424             644         819
## ctrl1016     119             315         413
# Apply crumblr transformation
# cobj is an EList object compatable with limma workflow
# cobj$E stores transformed values
# cobj$weights stores precision weights
cobj <- crumblr(cellCounts(pb))

Analysis

Now continue on with the downstream analysis

library(variancePartition)

fit <- dream(cobj, ~ StimStatus + ind, colData(pb))
fit <- eBayes(fit)

topTable(fit, coef = "StimStatusstim", number = Inf)
##                         logFC    AveExpr          t     P.Value  adj.P.Val         B
## CD8 T cells       -0.25085170  0.0857175 -4.0787416 0.002436375 0.01949100 -1.279815
## Dendritic cells    0.37386979 -2.1849234  3.1619195 0.010692544 0.02738587 -2.638507
## CD14+ Monocytes   -0.10525402  1.2698117 -3.1226341 0.011413912 0.02738587 -2.709377
## B cells           -0.10478652  0.5516882 -3.0134349 0.013692935 0.02738587 -2.940542
## CD4 T cells       -0.07840101  2.0201947 -2.2318104 0.050869691 0.08139151 -4.128069
## FCGR3A+ Monocytes  0.07425165 -0.2567492  1.6647681 0.128337022 0.17111603 -4.935304
## NK cells           0.10270672  0.3797777  1.5181860 0.161321761 0.18436773 -5.247806
## Megakaryocytes     0.01377768 -1.8655172  0.1555131 0.879651456 0.87965146 -6.198336

Given the results here, we see that CD8 T cells at others change relative abundance following treatment with interferon-β.

Session Info

## R version 4.4.1 (2024-06-14)
## Platform: aarch64-apple-darwin23.5.0
## Running under: macOS Sonoma 14.7.1
## 
## Matrix products: default
## BLAS:   /Users/gabrielhoffman/prog/R-4.4.1/lib/libRblas.dylib 
## LAPACK: /opt/homebrew/Cellar/r/4.4.2_2/lib/R/lib/libRlapack.dylib;  LAPACK version 3.12.0
## 
## locale:
## [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
## 
## time zone: America/New_York
## tzcode source: internal
## 
## attached base packages:
## [1] stats4    stats     graphics  grDevices utils     datasets  methods   base     
## 
## other attached packages:
##  [1] crumblr_0.99.14             muscData_1.20.0             scater_1.34.0              
##  [4] scuttle_1.16.0              zenith_1.8.0                ExperimentHub_2.14.0       
##  [7] AnnotationHub_3.14.0        BiocFileCache_2.14.0        dbplyr_2.5.0               
## [10] muscat_1.20.0               dreamlet_1.4.1              SingleCellExperiment_1.28.1
## [13] SummarizedExperiment_1.36.0 Biobase_2.66.0              GenomicRanges_1.58.0       
## [16] GenomeInfoDb_1.42.1         IRanges_2.40.1              S4Vectors_0.44.0           
## [19] BiocGenerics_0.52.0         MatrixGenerics_1.18.0       matrixStats_1.4.1          
## [22] variancePartition_1.36.3    BiocParallel_1.40.0         limma_3.62.1               
## [25] ggplot2_3.5.1              
## 
## loaded via a namespace (and not attached):
##   [1] fs_1.6.5                  bitops_1.0-9              httr_1.4.7               
##   [4] RColorBrewer_1.1-3        doParallel_1.0.17         Rgraphviz_2.50.0         
##   [7] numDeriv_2016.8-1.1       tools_4.4.1               sctransform_0.4.1        
##  [10] backports_1.5.0           utf8_1.2.4                R6_2.5.1                 
##  [13] metafor_4.6-0             lazyeval_0.2.2            mgcv_1.9-1               
##  [16] GetoptLong_1.0.5          withr_3.0.2               prettyunits_1.2.0        
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##  [34] gridGraphics_0.5-1        generics_0.1.3            shape_1.4.6.1            
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##  [52] crayon_1.5.3              lattice_0.22-6            beachmat_2.22.0          
##  [55] msigdbr_7.5.1             annotate_1.84.0           KEGGREST_1.46.0          
##  [58] pillar_1.9.0              knitr_1.49                ComplexHeatmap_2.22.0    
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