The FB2 cluster displayed enriched expression of the inflammation-associated genes CXCL and IL6. Importantly, subcluster FB3, which was significantly increased in AF, was enriched for AEBP1, a positive regulator of collagen fibrillogenesis via COL1A1 and COL3A1. FB4 cells express genes responsive to lipids, for example, APOE and PTGDS. FB5 cells highly express IGFBP6 and MFAP5, which are associated with growth factors. The gene discussed is APOE; the disease is atrial fibrillation.