The overall aim of this Program Project is to test further the hypothesis that mutations in the genes that encode for the extracellular components of articular cartilage, in particular the collagens of the tissue, cause heritable forms of osteoarthrits and related disorders of cartilage in man. The research focuses on diseases that produce degeneration of articular cartilage and that show dominant patterns of Mendelian inheritance. Therefore, it focuses on familial primary generalized osteoarthritis, the Wagner-Stickler syndrome or arthro-ophthalmopathy, and chondrodysplasias. Work completed during the last two years on the project has confirmed the hypothesis for at least a subset of the diseases. Analyses with restriction fragment length polymorphisms established linkage between the disease phenotype and the locus for the type II procollagen gene in a large family with primary generalized osteoarthritis associated with a mild chondrodysplasia. Cloning and sequencing of the gene then defined a mutation that caused the disease in the family. Similar studies in a family with the Stickler syndrome established linkage to the type II procollagen gene and then cloning and sequencing of the gene defined the mutation causing the disease. The present proposal is to complete the next necessary step on the work: It will define how many families with primary generalized osteoarthritis do in fact have a mutation in the type II procollagen gene or related genes expressed in cartilage. It will also define the spectrum of mutations that cause more rare diseases of cartilage and related tissues such as the Stickler syndrome and chondrodysplasias. The work proposed includes additional linkage analyses of families, definition at the cellular and molecular level of how mutations produce their devastating effects in cartilage, precise definition of mutations by extensive sequencing of genes with new technologies recently developed in our laboratory and others, and expression of the mutated genes in transgenic mice in order to create animal models for the human diseases. The results will provide simple and definitive DNA tests for molecular definition of the diseases in patients. They will provide fundamental information about the structure-function relationships of type II procollagen and other macromolecules of collagen that cannot be obtained in any other way. Finally, they will also provide authentic animal models for the human diseases that will be useful for testing of new medications for the diseases and for future considerations of gene therapy in man.
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