Osteogenesis imperfecta mutations may probe vital functional domains (e.g. proteoglycan binding sites) of type I collagen fibrils.

Osteogenesis imperfecta (OI) is a disease characterized by bone malformations caused by mutations in type 1 collagen.(1) Since many of the 338 possible glycine mutations have not been observed in clinical practice, is this due to chance alone? Because only 83 mutations have been reported in 126 patients, we conclude that many mutations are absent from clinical data for non-random causes. Mutations affecting vital intermolecular interactions in the extracellular matrix (e.g. potential collagen binding sites for proteoglycans) may result in non-viable fetuses that do not progress to clinical status. Some mutations may be silent because they do not significantly affect normal function. The total number of clinically active mutations that will be observed may be far fewer than the potential 338 maximum.