Thirty-three novel COL1A1 and COL1A2 mutations in patients with osteogenesis imperfecta types I-IV.

Osteogenesis imperfecta (OI) is a heritable disease of bone characterized by low bone mass and bone fragility. Six different types of OI have been described to date, based on clinical phenotype and histological findings. The genetic defect in many patients with OI types I-IV is due to mutations in the genes encoding type I collagen, while patients with OI types V and VI show no evidence of mutations in the COL1A1/COL1A2 genes. Here we report thirty-three novel mutations in patients with types I-IV OI. Sixteen mutations were in COL1A1 and seventeen were in COL1A2. Most mutations resulted in substitutions for glycine: one of these, a doublet GG>CC transversion, created a unique Gly-->Pro missense mutation in the triple helical domain of COL1A2. Two rare triple helical Gly-->Glu substitutions in COL1A2 are also described. In addition, there were six single-base deletion mutations resulting in frameshifts, seven splice junction mutations, and a 9-bp triple helix insertion associated with a severe (OI II) phenotype. The variety of mutations described in the COL1A1/COL1A2 genes giving rise to an OI phenotype is in accordance with the clinical heterogeneity of the disease. Hum Mutat 17:434, 2001.