COL21A1 and osteogenesis imperfecta: Based on the integrated result of the protein–protein network (14 interactive proteins from the predicted gene set A) and pathway enrichment analysis (3 interactive proteins from the predicted gene set B), we finally identified 15 genes (ADAMTS2, ADAMTS3, ADAMTS14, COL4A6, COL5A2, COL8A1, COL19A1, COL20A1, COL21A1, COL22A1, COL24A1, COL27A1, COL28A1, TLL1, WNT8B) as the potential causal genes to OI disease.