FMO5 and atrial fibrillation: We also performed niche analysis using just FMO5+ AT2s, CFTR+ AT2s, AF-c1/2, and AF-c3 cells, which identified two alveolar niches defined by the association of FMO5+ AT2s with AF-c1/2 cells, and CFTR+ AT2s with AF-c3 cells, concurring with our analysis using cell type identities inferred by label transfer (Fig. S3F–H).