GPC4 and rheumatoid arthritis: The KEGG pathways (Supplementary Table 3) that were enriched by the group of genes that showed strong positive correlations include the glycosaminoglycan degradation pathway (HEXA and HGSNAT), the rheumatoid arthritis pathway (CTSK and ATP6V family), inflammation-related pathways (GSK3B, NCK2, HRH1, and ITPR1), Wnt signaling pathways (APCDD1L, FZD1, GPC4, GSK3B, and MMP7), hedgehog signaling pathway (EVC and GSK3B), and PPAR signaling pathways (ACSL1, FABP4, and PLIN2).