COL1A1 and osteogenesis imperfecta: Studies have revealed that patients with osteogenesis imperfecta (OI) primarily exhibit mutations in the collagen type 1 alpha 1 chain (COL1A1) gene or the collagen type 1 alpha 2 chain (COL1A2) gene, which are associated with the lower trabecular number, trabecular thickness, bone mass, and connectivity in the SB.