Collagen mutations in bone matrix dysfunction

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This project is a biochemical investigation of collagen, which is the principle protein of bone, joints, blood vessels and skin. More than 200 mutations have been identified in the genes for type I collagen that result in Osteogenesis Imperfecta (OI), otherwise known as brittle-bone disease, in children and adults. However, very little is known about how these mutations cause bones to be brittle and why the disease varies so widely in severity. Our experiments are directed towards a better understanding of how bone cells respond to the mutant collagen and how these mutations actually result in brittle bones. We know that the majority of OI-causing mutations typically lead to a severe OI because the mutant collagen interferes with normal functioning of the matrix and effectively weakens it. We will examine how the mutant collagen disrupts normal cell function using bone and skin cell lines in which we have added a mutated collagen gene. The mutations we will introduce are the same ones that cause OI in patients. The experiments cannot be carried out with OI cell lines isolated from humans because it is very difficult to identify the mutant collagen in the matrix. Instead we have engineered a marker into the mutant collagen to allow the mutant collagen to be easily tracked. We will then examine how the presence of the mutant collagen affects matrix integrity, turnover and the formation of mutant matrix. In the second part of the study we will make a transgenic mouse that carries a specific collagen mutation. This will allow us to examine the fate of mutant collagen in a whole animal. As with the engineered cells described above, the mutant collagen will be altered to allow easy tracking. Collectively, these experiments will provide valuable information about how the presence mutant collagen disprupts integrity of the extracellular matrix of skin and bone.