In the study, mice were genetically engineered by the Baylor team with the CRTAP gene removed, and then monitored for signs of abnormalities. Results showed that the mice were unable to properly line up the fibers that make up collagen using an enzyme called 3-prolyl hydroxylase, which they determined needs to bind to CRTAP for it to function normally. As a result of the loss of normal 3-prolyl hydroxylase function, the cells that build bone (osteoblasts) were found to make thicker collagen fibers, but fewer of them, resulting in weaker bone.
Boyce and his group in the Center for Musculoskeletal Research at the Medical Center characterized the skeletal abnormalities in the genetically engineered mice and carried out studies of bone cells from the mice as well as detailed microscopic analysis of their bones. They found that, without this key gene, mice developed osteoporosis due to defects in their osteoblasts. Another team working at McGill University in Montreal identified human patients who had OI due to mutations in CRTAP, demonstrating for the first time that CRTAP has an essential function in humans.
In addition, the findings of the current study provide the first proof that osteogenesis imperfecta can be inherited in a recessive manner. Previously, the genes known to be involved in OI were dominant, meaning that if you had a defect in the gene in your chromosome, you developed the disease. That left open the possibility that the mutation causing OI was spontaneous, that something went wrong for the first time in the gene of the person developing it, and not inherited from parents.
The newly discovered gene however is a recessive trait, signifying that the disease can be passed down generation to generation,
Source:University of Rochester Medical Center