Multi-Omics Integration (MOFA+)

Multi-Omics Integration (MOFA+)

Identify latent factors driving variation across 2+ omics layers using MOFA+ (Multi-Omics Factor Analysis). Decomposes multi-omics data into interpretable factors, each capturing shared or view-specific biological signal. Handles missing data across views natively.

When to Use This Skill

Use when you:

• ✅ Have 2+ omics layers measured on overlapping samples (RNA-seq + proteomics, methylation + mutations, etc.)
• ✅ Want to find shared sources of variation across omics (not just per-omics analysis)
• ✅ Need to identify which omics layers contribute to each source of variation
• ✅ Have incomplete data (not all samples measured in all views) — MOFA handles this
• ✅ Want factor scores for downstream patient stratification or survival analysis

Don't use for:

• ❌ Single omics data (use bulk-rnaseq-counts-to-de-deseq2 or bulk-omics-clustering)
• ❌ Supervised prediction (use lasso-biomarker-panel instead)
• ❌ Single-cell multi-modal (MOFA2 supports it, but consider scrna-trajectory-inference)
• ❌ Fewer than 10 samples per view

Runtime: ~5-8 minutes total (CLL example). First run adds ~1-3 min for Python environment setup.

Installation

# Bioconductor packages
if (!requireNamespace("BiocManager", quietly = TRUE)) install.packages("BiocManager")
BiocManager::install(c("MOFA2", "MOFAdata", "ComplexHeatmap"))

# CRAN packages
install.packages(c("ggprism", "circlize", "reshape2", "RColorBrewer"))

Inputs

• Multi-omics data: Named list of matrices (features × samples), one per omics view
  • Minimum 2 views, any combination of omics types
  • Samples as columns, features as rows
  • Missing samples across views OK (MOFA handles incomplete overlap)
• Sample metadata (optional): CSV/TSV with sample IDs + clinical variables (for factor-trait associations)
• Supported formats: R matrices, CSV/TSV files, or MultiAssayExperiment

Outputs

Analysis objects (RDS):

• mofa_model.rds — Complete trained MOFA model for downstream use
  • Load with: model <- readRDS('mofa_results/mofa_model.rds')
  • Required for: bulk-omics-clustering (factor-based clustering), lasso-biomarker-panel (feature selection)

CSV results:

• factor_values.csv — Sample factor scores (samples × factors)
• weights_*.csv — Feature weights per view (features × factors)
• variance_explained_per_factor.csv — R² per factor per view
• variance_explained_total.csv — Total R² per view
• top_features_per_factor.csv — Top 20 features per factor per view

Visualizations (PNG + SVG):

• mofa_variance_per_factor — Heatmap: R² per factor per view (signature MOFA plot)
• mofa_total_variance — Bar chart: total R² per view
• mofa_factor_scatter — Scatter: Factor 1 vs 2 colored by clinical variable
• mofa_factor_correlation — Tile: factor-factor correlations
• mofa_top_weights — Faceted bar: top feature weights per factor
• mofa_factor_heatmap — ComplexHeatmap: factors × samples with annotations
• mofa_factor_clinical — Box plots: factor values by clinical groups

Reports:

• analysis_report.md — Markdown summary with methods, results, references
• analysis_report.pdf — PDF report with embedded figures (requires rmarkdown + LaTeX)

Clarification Questions

1. Input Files (ASK THIS FIRST):
   • Do you have multi-omics data matrices to integrate?
   • Expected: Named list of matrices (features × samples), or CSV files per omics view
   • Or use example data? CLL blood cancer dataset (200 patients: mRNA, methylation, mutations, drug response)

🚨 IF EXAMPLE DATA SELECTED: Skip questions 3-4. Proceed directly to Step 1.

2. Analysis Options:

   • (If using example data) Number of factors:
     • a) 15 factors — standard analysis (recommended)
     • b) 5 factors — quick demo (~2 min faster)
   • (If using own data) Number of factors:
     • a) 15 (recommended starting point)
     • b) Custom number

3. (Own data only) Data types per view:

   • Which omics types? (RNA-seq, proteomics, methylation, mutations, metabolomics, drug response, other)
   • Are any views binary (0/1)? MOFA uses Bernoulli likelihood for binary data.

4. (Own data only) Sample metadata:

   • Do you have a sample metadata file (CSV/TSV) with clinical variables?
   • Variables for factor-trait associations (e.g., disease status, treatment, subtype)?

Standard Workflow

Note: Run from the OmicsClaw root directory and add the workflow scripts to sys.path:

import sys; import os; sys.path.insert(0, os.path.abspath('knowledge_base/scripts/multi-omics-integration'))

🚨 MANDATORY: USE SCRIPTS EXACTLY AS SHOWN - DO NOT WRITE INLINE CODE 🚨

Step 1 - Load data:

# For CLL example data:
source("scripts/load_example_data.R")
cll <- load_cll_data()

# For user data:
# source("scripts/load_example_data.R")
# cll <- load_user_data(
#   file_paths = list(RNA = "rna.csv", Protein = "protein.csv"),
#   metadata_path = "metadata.csv"
# )

✅ VERIFICATION: "✓ Data loaded successfully!" with per-view dimensions

Step 2 - Run MOFA analysis:

source("scripts/mofa_workflow.R")
model <- run_mofa_analysis(
    data_list = cll$data,
    metadata = cll$metadata,
    n_factors = 15,
    output_dir = "mofa_results"
)

DO NOT write inline MOFA code. Just call run_mofa_analysis().

⏱️ Takes ~2-5 min (+ ~1-3 min extra on first run for Python environment setup via basilisk).

✅ VERIFICATION: "✓ MOFA model trained successfully!" with variance explained summary

Step 3 - Generate visualizations:

source("scripts/mofa_plots.R")
generate_all_plots(model, output_dir = "mofa_results")

🚨 DO NOT write inline plotting code (ggsave, ggplot, Heatmap, etc.). Just use the script. 🚨

The script handles PNG + SVG export with graceful fallback for SVG dependencies.

✅ VERIFICATION: "✓ All plots generated successfully!" with file count

Step 4 - Export results:

source("scripts/export_results.R")
export_all(model, output_dir = "mofa_results")

DO NOT write custom export code. Use export_all().

✅ VERIFICATION: "=== Export Complete ===" with file list

⚠️ CRITICAL - DO NOT:

• ❌ Write inline MOFA code → STOP: Use run_mofa_analysis()
• ❌ Write inline plotting code (ggsave, ggplot, Heatmap, etc.) → STOP: Use generate_all_plots()
• ❌ Write custom export code → STOP: Use export_all()
• ❌ Try to install basilisk/reticulate manually → MOFA2 handles Python automatically

⚠️ IF SCRIPTS FAIL - Script Failure Hierarchy:

1. Fix and Retry (90%) — Install missing package, re-run script
2. Modify Script (5%) — Edit the script file itself, document changes
3. Use as Reference (4%) — Read script, adapt approach, cite source
4. Write from Scratch (1%) — Only if genuinely impossible, explain why

NEVER skip directly to writing inline code without trying the script first.

Common Issues

Interpretation Guide

Variance Decomposition (Key MOFA Output)

• High R² in one view: Factor captures view-specific variation
• High R² across views: Factor captures shared cross-omics signal (most interesting)
• Low total R²: MOFA explains little variation in that view — consider adding features or views

Factor Interpretation

See: references/mofa-interpretation-guide.md for detailed downstream analysis.

Suggested Next Steps

After running MOFA:

• Patient stratification: Use bulk-omics-clustering on factor scores to define molecular subtypes
• Biomarker discovery: Use lasso-biomarker-panel on top-weighted features per factor
• Pathway enrichment: Use functional-enrichment-from-degs on top mRNA features per factor
• Network analysis: Use coexpression-network on factor-associated genes
• Survival analysis: Use survival-analysis-clinical with factor scores as covariates

Related Skills

References

• Argelaguet R, et al. (2020) MOFA+: a statistical framework for comprehensive integration of multi-modal single-cell data. Genome Biology 21:111.
• Argelaguet R, et al. (2018) Multi-Omics Factor Analysis—a framework for unsupervised integration of multi-omics data sets. Molecular Systems Biology 14:e8124.
• Dietrich S, et al. (2018) Drug-perturbation-based stratification of blood cancer. Journal of Clinical Investigation 128(1):427-445.