hdwgcna

name

hdwgcna

description

Co-expression network analysis for single-cell and spatial transcriptomics using hdWGCNA (R/Seurat). Covers the full pipeline — metacell construction, soft-power selection, network construction, module identification, module eigengenes (MEs/hMEs), hub gene scoring — plus three downstream analyses: differential module eigengenes between groups (FindDMEs / FindAllDMEs), module-trait correlation (ModuleTraitCorrelation), and enrichment via Enrichr / fgsea. Operates on Seurat objects.

hdWGCNA: High-Dimensional Co-Expression Network Analysis

Overview

hdWGCNA is the modern adaptation of WGCNA for high-dimensional transcriptomics — single-cell RNA-seq, single-nucleus RNA-seq, and spatial transcriptomics. It solves WGCNA's two biggest problems with single-cell data:

1. Sparsity — single cells have many zeros, breaking WGCNA's correlation structure. hdWGCNA aggregates similar cells into "metacells" first.
2. Batch effects — module eigengenes (MEs) can be confounded by donor/sample. hdWGCNA computes batch-corrected harmonized MEs (hMEs) via Harmony.

The package operates on Seurat objects: every step adds data to seurat_obj@misc[[wgcna_name]], so you can run multiple parallel analyses (e.g. one network per cell type) on the same Seurat object.

When to Use This Skill

• Identifying co-expressed gene modules within a cell type (e.g. "neuronal modules in inhibitory neurons")
• Finding hub genes (genes most central to a module) for downstream wet-lab validation
• Testing module activity differences between conditions (case vs control, treated vs untreated)
• Correlating module eigengenes with continuous traits (age, disease severity, cell type proportion)
• Functional enrichment of modules (GO, KEGG, custom gene sets) via Enrichr or fgsea
• Module preservation testing across datasets (cross-condition / cross-species)

Not for: bulk RNA-seq (use vanilla WGCNA), trajectory analysis (use scVelo / Slingshot), differential expression at the gene level (use Seurat / DESeq2).

Prerequisites

• R ≥ 4.2, Seurat ≥ 4.x, WGCNA, harmony, UCell, igraph
• A Seurat object with: cell type / cluster labels, sample/donor identifiers, PCA + Harmony reductions if you want hMEs
• Recommend ≥ 5,000 cells per group of interest after QC

# Install (one-time)
install.packages("BiocManager")
BiocManager::install(c("WGCNA", "GeneOverlap", "UCell"))
devtools::install_github('smorabit/hdWGCNA', ref='dev')

Quick Start — Full Pipeline

library(Seurat)
library(hdWGCNA)
library(tidyverse)
library(cowplot)
library(patchwork)
library(WGCNA)
allowWGCNAThreads(nThreads = 8)

# Assumes you already have a normalized Seurat object with cell type labels.
seurat_obj <- readRDS('your_annotated_seurat.rds')

# ── 1. Set up hdWGCNA experiment ───────────────────────────────────────────
seurat_obj <- SetupForWGCNA(
  seurat_obj,
  gene_select = "fraction",     # keep genes expressed in ≥ fraction of cells
  fraction = 0.05,
  wgcna_name = "INH"             # name this analysis (you can run multiple)
)

# ── 2. Build metacells ─────────────────────────────────────────────────────
# k-NN aggregation within each (cell_type × Sample) bin → "metacells"
# reduces sparsity while keeping per-sample biology distinct.
seurat_obj <- MetacellsByGroups(
  seurat_obj,
  group.by = c("cell_type", 
  reduction           
  k                          
  max_shared                 
  ident.group  

seurat_obj  NormalizeMetacellsseurat_obj


seurat_obj  SetDatExpr
  seurat_obj
  group_name              
  group.by  
  assay  
  layer  



seurat_obj  TestSoftPowersseurat_obj networkType  
plot_list  PlotSoftPowersseurat_obj
wrap_plotsplot_list ncol  



seurat_obj  ConstructNetwork
  seurat_obj
  tom_name                
  overwrite_tom  

PlotDendrogramseurat_obj main  


seurat_obj  ScaleDataseurat_obj features  VariableFeaturesseurat_obj
seurat_obj  ModuleEigengenes
  seurat_obj
  group.by.vars        



seurat_obj  ModuleConnectivity
  seurat_obj
  group.by  
  group_name  

seurat_obj  ResetModuleNamesseurat_obj new_name  


hub_df  GetHubGenesseurat_obj n_hubs  


libraryUCell
seurat_obj  ModuleExprScoreseurat_obj n_genes   method  


saveRDSseurat_obj 

The result object is the same Seurat object, with the entire hdWGCNA experiment stored in seurat_obj@misc[["INH"]]. Inspect the three key outputs:

# Module assignments (one row per gene)
modules <- GetModules(seurat_obj) %>% subset(module != 'grey')
head(modules)
#   gene_name  module    color   kME_INH-M1   kME_INH-M2 ...
# 1 GRIN1      INH-M1    red     0.332        0.021
# 2 INTS11     INH-M2    blue    0.050        0.227

# Module eigengenes (cells × modules)
hMEs <- GetMEs(seurat_obj)             # harmonized
MEs  <- GetMEs(seurat_obj, harmonized = FALSE)   # raw

# Hub genes (top N per module by kME)
hub_df <- GetHubGenes(seurat_obj, n_hubs = 25)

Convenience runner: Rscript scripts/build_network.R --rds annotated.rds --cell-type INH --out seurat_hdwgcna.rds. See references/network_construction.md for parameter tuning, metacell diagnostics, and gotchas.

---

Downstream 1 — Differential Module Eigengenes (DMEs)

The question: does module-N activity differ between condition A and condition B (e.g. AD vs control, treated vs untreated)? This is the most common follow-up after network construction.

Two-group test — FindDMEs

# Pick the cells to compare. Often: same cell type, two conditions.
group1 <- [e-mail] %>%
  filter(cell_type == 'INH', condition == 'AD')   %>% rownames()
group2 <- [e-mail] %>%
  filter(cell_type == 'INH', condition == 'Ctrl') %>% rownames()

DMEs <- FindDMEs(
  seurat_obj,
  barcodes1 = group1,
  barcodes2 = group2,
  test.use  = 'wilcox',          # Mann-Whitney U
  pseudocount.use = 0.01,        # for log2FC stability
  wgcna_name = 'INH'
)

Returns a dataframe with one row per module: p_val, avg_log2FC, pct.1, pct.2, p_val_adj, module. The pct.* columns are the fraction of cells in each group whose ME is non-zero — useful when a module is "active" in one condition but silent in the other.

Visualize

PlotDMEsLollipop(seurat_obj, DMEs, group.by = 'cell_type', wgcna_name = 'INH')
PlotDMEsVolcano (seurat_obj, DMEs, plot_labels = TRUE,    wgcna_name = 'INH')

The lollipop is for a single comparison (great for figures). The volcano shows effect-size × significance at a glance — useful when you have many modules and want to spot the outliers.

One-vs-all — FindAllDMEs

Across each level of a grouping variable, runs that level vs all other cells:

DMEs_all <- FindAllDMEs(
  seurat_obj,
  group.by   = 'cell_type',
  wgcna_name = 'INH'
)
# adds a `group` column with the tested category

Module signature scores instead of MEs

If your modules don't have clean eigengenes (e.g. small modules with noisy first PC), test on UCell-based hub-gene signatures instead:

seurat_obj <- ModuleExprScore(seurat_obj, n_genes = 25, method = 'UCell')
DMEs_scores <- FindDMEs(
  seurat_obj,
  barcodes1 = group1, barcodes2 = group2,
  features  = 'ModuleScores',
  wgcna_name = 'INH'
)

Convenience: Rscript scripts/downstream_analyses.R --rds seurat_hdwgcna.rds --task dme --group-by condition --group1 AD --group2 Ctrl --cell-type INH

Source: hdWGCNA Differential MEs tutorial.

---

Downstream 2 — Module–Trait Correlation

The question: which modules correlate with continuous or ordered phenotypes (age, Braak stage, disease severity, % tumor cells per spot)?

cur_traits <- c('age', 'Braak_stage', 'sex_binary', 'cell_density')

seurat_obj <- ModuleTraitCorrelation(
  seurat_obj,
  traits   = cur_traits,
  group.by = 'cell_type',         # stratify the correlation by cell type
  wgcna_name = 'INH'
)

mt_cor <- GetModuleTraitCorrelation(seurat_obj)
# mt_cor is a list:
#   mt_cor$cor   — correlation coefficients (one matrix per group)
#   mt_cor$pval  — p-values
#   mt_cor$fdr   — FDR-corrected

PlotModuleTraitCorrelation(
  seurat_obj,
  label        = 'fdr',           # or 'pval' or 'cor'
  label_symbol = 'stars',         # *** < 0.001, ** < 0.01, * < 0.05
  text_size    = 2.5,
  high_color   = 'yellow',
  mid_color    = 'black',
  low_color    = 
  plot_max                   
  combine                    

Trait type compatibility

Trait type	Supported?	Notes
Continuous (numeric)	✅	Use as-is
Binary categorical	✅	Convert to 0/1 before passing
Ordered categorical	✅	Convert to factor with explicit levels = c('low', 'mid', 'high'), then as.numeric()
Unordered categorical (>2 levels)	❌	The correlation is meaningless. Either dummy-encode or skip.

Sample ID, mouse strain, batch — these are unordered categorical; if you want to test for batch effects on modules, use ANOVA via FindDMEs between groups instead.

Convenience: Rscript scripts/downstream_analyses.R --rds seurat_hdwgcna.rds --task trait --traits age,Braak_stage

Source: hdWGCNA Module-Trait Correlation tutorial.

---

Downstream 3 — Functional Enrichment

The question: what biological processes / pathways does each module represent?

Enrichr (web-based, fast, comprehensive)

library(enrichR)

dbs <- c(
  'GO_Biological_Process_2023',
  'GO_Cellular_Component_2023',
  'GO_Molecular_Function_2023',
  'KEGG_2021_Human',
  'Reactome_2022',
  'WikiPathway_2023_Human'
)

seurat_obj <- RunEnrichr(
  seurat_obj,
  dbs        = dbs,
  max_genes  = 100,                # genes per module sent to Enrichr (sorted by kME)
  wgcna_name = 'INH'
)

enrich_df <- GetEnrichrTable(seurat_obj)
# Columns: Term, Overlap, P.value, Adjusted.P.value, Odds.Ratio, Combined.Score, Genes, db, module

Visualize

# Per-module bar plots — writes one PDF per module to outdir/
EnrichrBarPlot(
  seurat_obj,
  outdir     = 'figures/enrichr/',
  n_terms    = 10,
  plot_size  = c(5, 7),
  logscale   = TRUE,
  wgcna_name = 'INH'
)

# Single dot plot across all modules (great for figures)
EnrichrDotPlot(
  seurat_obj,
  mods       = 'all',
  database   = 'GO_Biological_Process_2023',
  n_terms    = 2,                # top N per module
  term_size  = 8,
  p_adj      = FALSE,
  wgcna_name = 'INH'
)

GSEA via fgsea (when you have a ranked gene list)

For a continuous test (not over-representation), rank genes by kME within a module and use fgsea against any MSigDB collection:

library(fgsea)
library(msigdbr)

# Pull genes ranked by kME in module of interest
modules <- GetModules(seurat_obj) %>% filter(module != 'grey')
target_mod <- 'INH-M3'
ranks <- modules %>%
  arrange(desc(.data[[paste0('kME_', target_mod)]])) %>%
  pull(.data[[paste0('kME_', target_mod)]], name = gene_name)

# Get pathways from MSigDB
pathways <- msigdbr(species = 'Homo sapiens', category = 'H') %>%
  split(x = .$gene_symbol, f = .gs_name

gsea_res  fgseapathways ranks minSize   maxSize  
headgsea_resorderpadj

Convenience: Rscript scripts/downstream_analyses.R --rds seurat_hdwgcna.rds --task enrich --dbs GO_Biological_Process_2023,KEGG_2021_Human

Source: hdWGCNA Enrichment tutorial.

---

Visualization Cookbook

Module feature plot (UMAP × module)

plot_list <- ModuleFeaturePlot(seurat_obj, features = 'hMEs', order = TRUE)
wrap_plots(plot_list, ncol = 6)
# Alternatives: features = 'scores' (UCell hub scores), 'MEs' (raw, no Harmony)

Module dot plot across cell types

hMEs <- GetMEs(seurat_obj, harmonized = TRUE)
modules <- GetModules(seurat_obj)
mods <- levels(modules$module); mods <- mods[mods != 'grey']
[e-mail] <- cbind([e-mail], hMEs)
DotPlot(seurat_obj, features = mods, group.by = 'cell_type') +
  RotatedAxis() +
  scale_color_gradient2(high = 'red', mid = 'grey95', low = 'blue')

Hub gene network (top hubs from each module)

ModuleNetworkPlot(seurat_obj, n_hubs = 5)              # one figure per module
HubGeneNetworkPlot(seurat_obj, n_hubs = 5, n_other = 10)   # multi-module network

Module–module correlation

ModuleCorrelogram(seurat_obj, features = 'hMEs')

Module radar plot across cell subtypes

ModuleRadarPlot(
  seurat_obj,
  group.by = 'cluster_label',
  barcodes = [e-mail] %>% filter(cell_type == 'INH') %>% rownames(),
  axis.label.size = 4
)

More patterns + custom layouts in references/plotting_guide.md.

---

Key Parameters to Adjust

Metacell construction (MetacellsByGroups)

• k (default 25): cells per metacell. Lower → finer resolution but noisier. For small datasets (< 2000 cells/type), drop to 10–15.
• max_shared (default 10): caps cell sharing across metacells. Higher → fewer metacells but more redundancy.
• group.by: always include both cell type and sample — otherwise metacells will mix donors and you'll lose biology.

Soft power

• The plot from PlotSoftPowers should show R² climbing past 0.8. Pick the lowest power that crosses this threshold.
• Default networkType='signed' (recommended). 'unsigned' collapses positive and negative correlations — usually wrong.

Network construction (ConstructNetwork)

• minModuleSize (default 50): smallest allowed module. Reduce for small datasets.
• mergeCutHeight (default 0.2): merges similar modules. Increase (0.3–0.4) to consolidate noisy modules.
• deepSplit (0–4): how aggressively to split. 2 is default; 4 produces many tiny modules.

Module eigengenes (ModuleEigengenes)

• group.by.vars: pass your batch/donor variable. Without this you get raw MEs (MEs) — use harmonized (hMEs) for downstream stats.

kME / hub genes

• n_hubs (default 25 for ModuleExprScore): how many top-kME genes count as "the module's signature". 25 is a good default; for sparse single-cell data, 50 makes the signature more stable.

---

Best Practices

• Run one network per major cell type, not one big network across all cells. WGCNA's TOM is dominated by cell-type identity otherwise — the "modules" will just be marker-gene signatures for each cell type rather than meaningful within-cell-type co-expression.
• Save the Seurat object after ConstructNetwork. It's the slow step — minutes to hours depending on n cells and n genes. Everything downstream (MEs, kME, hubs, DMEs, enrichment) is fast.
• The grey module is the dumping ground for unassigned genes. Always subset(module != 'grey') before downstream analyses.
• Inspect PlotDendrogram BEFORE downstream analysis. If the dendrogram has one giant module and a tiny grey blob, your soft power is too low. If it has 30+ skinny modules, soft power is too high or minModuleSize is too small.
• For module-trait correlation with categorical traits, dummy-encode unordered factors instead of relying on alphabetical order. Otherwise the correlation is meaningless.
• Cross-condition module preservation matters. A module discovered in controls may not exist in cases. Test with ModulePreservation before trusting cross-condition DME results.

---

End-to-End Template

assets/hdwgcna_template.R is a single parameterized script — set the variables at the top (input .rds, cell type, sample column, condition column) and run end-to-end through DME + module-trait correlation + Enrichr.

Rscript assets/hdwgcna_template.R

Convenience Scripts

• scripts/build_network.R — network construction only (the slow step). Saves an annotated Seurat object.
• scripts/downstream_analyses.R — DME / module-trait / enrichment. Subtask selected via --task dme|trait|enrich|all.

---

References

• hdWGCNA documentation — Morabito et al., main project site
• Basic tutorial
• Differential Module Eigengenes
• Module–Trait Correlation
• Enrichment Analysis
• Original WGCNA: Langfelder & Horvath (2008), BMC Bioinformatics
• hdWGCNA paper: Morabito, Reese, Rahimzadeh et al. (2023), Cell Reports Methods