Bone fragments from tibias or femurs were collected from 10 children with OI type III (9 with glycine substitution mutations in COL1A1 or COL1A2 and 1 with valine deletion in COL1A2) and 4 children who were not affected by OI (Supplemental Table 1; supplemental material available online with this article; https://doi.org/10.1172/JCI152571DS1). Here, COL1A1 is linked to osteogenesis imperfecta type 3.