COL1A1 and osteogenesis imperfecta: Research advances have shown that different genetic mutations acting through shared molecular pathways can cause similar skeletal phenotypes [e.g., osteogenesis imperfecta (OI) results from disruptions in genes encoding type I collagen (COL1A1 and COL1A2) and genes encoding molecular chaperones (e.g., SERPINH1 and FKBP10)], as well as that different skeletal dysplasias can result from mutations in the same gene (e.g., mutations in the FGFR3 cause achondroplasia, hypochondroplasia, and thanatophoric dysplasia) (6, 7).