TYPE-II COLLAGEN PRO-ALPHA-CHAINS CONTAINING A GLY574SER MUTATION ARENOT INCORPORATED INTO THE CARTILAGE MATRIX OF TRANSGENIC MICE

The biochemical consequences of a type II procollagen mutation that co ntained a Gly574Ser amino acid substitution were analyzed in a transge nic mouse strain. The mutation correlated with one previously characte rized in a patient with the lethal human chondrodysplasia, hypochondro genesis (Horton et al., 1992), and resulted in a similar shortlimbed p henotype. There were fewer collagen fibrils present in the transgenic cartilage and reduced immunofluorescence of cartilage matrix using a t ype II collagen antibody. Pepsin-extracted collagen from transgenic mo use embryo cartilage was analyzed electrophoretically and indicated le ss type II as well as type XI collagen compared to their wild-type lit termates. A pulse-chase experiment was performed to evaluate the biosy nthesis and fate of type II collagen. Chondrocytes isolated from trans genic tissue synthesized fewer stable molecules, resulting in decrease d secretion of the procollagen chains. By amino acid sequence analysis of the type II collagen peptides from cartilage of transgenic mouse e mbryos, serine was not detected at residue 574, the site mutated in th e transgene. Based on sequence data, we believe that the molecules inc orporated into collagen fibrils of the extracellular matrix, while few er in number, were composed of normal alpha 1(II) chains.