POSTN and systemic lupus erythematosus: We then subsetted and re-clustered fibroblasts from patients (n = 82) in the AMP RA/SLE single-cell RNA sequencing dataset15 that were highly enriched for the fibrogenic gene signature (top 10% of cells) and observed two broad fibrogenic fibroblast clusters – one marked by high COMP expression and another marked by high POSTN expression (Fig. 2a–b).