easy bruising. Two of the patients experienced vascular rupture. We show that all mutations interfere with removal of the procollagen-I-N propeptide, even though the N-proteinase cleavage site remains intact. Incorporation of these uncleaved pN-collagen chains into the mature collagen fibrils results in restricted lateral growth of these fibrils, as evidenced by decreased dermal fibril diameters in vivo. While these helical mutations are directly responsible for the OI-features, they are, by interference of N-propeptide removal, indirectly responsible for the EDS features. doi:10.1016/j.matbio.2006.08.183 161 Conditional expression of collagen II mutants in SW1353 cells A. Steplewski, V. Hintze, R.J.Brittingham, K. Holmes, A. Fertala Department of Dermatology and Cutaneous Biology, Thomas Jefferson University, Philadelphia, PA 19107, United States Mutations in collagen II are associated with chondrodys- plasias. It is expected that pathological effects of collagen mutations can be counterbalanced by gene or cell therapy approaches. Due to a number of limitations, which include problems with delivery of therapeutic agents into patients, transgenic mice harboring collagen II mutations, and native chondrocytes molecular targets that have to be reached in order to change diseased phenotype have not been defined. We developed an experimental model that will allow us to test gene and cell therapy approaches aimed at alleviating the effects of the presence of mutant collagen II molecules. We designed DNA constructs for R75C, R519C, R789C, and G853E collagen II mutants found in chondrodysplasia patients under a Tet-responsive promoter. These constructs were designed to be expressed in the SW1353 chondrocytic cell line, which forms cartilage-like constructs in 3D cultures. We tested the behavior of these cells and the morphology of cartilage-like constructs formed in conditions allowing expression of recombinant collagen II. Subsequently, the behavior of cells and the morphological changes were monitored in these 3D constructs after switching off expression of exogenous collagen II. We demonstrated great utility of this system for studies on the effects of blocking expression of mutant collagen II on repair of damaged cartilaginous tissues. Moreover, we demonstrated a great utility of this system for defining minimal therapeutic targets that have to be reached to change a diseased phenotype caused by collagen II mutants. doi:10.1016/j.matbio.2006.08.184 162 ADAMTS10 interacts with fibrillin in Weill-Marchesani syndrome W.E. Kutz a , L.W. Wang a , D.R. Keene b , L.Y. Sakai b , S.S. Apte a a Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, United States b Shriners Hospital for Children, Portland, OR 97239, United States Mutations in ADAMTS10 or fibrillin-1 cause the recessive and dominant forms of Weill-Marchesani syndrome (WMS), respec- tively. WMS is a rare connective tissue disorder characterized by short stature, brachydactyly, ectopia lentis, and aortic stenosis. In most respects, WMS is the opposite of Marfan syndrome (MFS), a more common connective tissue disorder caused by dominant mutations in fibrillin-1. Given this genetic evidence, we hypothe- size that ADAMTS10 and fibrillin-1 proteins interact to regulate extracellular networks in connective tissues. Adamts10 mRNA, like fibrillin-1, was widely expressed in tissues relevant to WMS and MFS, such as aorta, lung, skin and the skeleton. Using blot overlay assays and BIAcore, we found that ADAMTS10 binds to the N-and C-terminal halves of fibrillin-1. Binding was specific to ADAMTS10, as ADAMTS1, 2, 4, 5, and 13 did not bind to fibrillin-1. In tissues, light and immuno-EM showed specific immunolocalization of ADAMTS10 along fibrillin microfibrils. Cell-based proteolysis assays suggested furin-activated ADAMTS10 is capable of cleaving the C-terminal portion of fibrillin-1. Lastly, immunocytochemistry of WMS patient cells, as well as MEFS from TS10-/- mice showed disorganized and sometimes absent fibrillin- 1 matrices. These results suggest an intimate relationship between ADAMTS10 and fibrillin-1, with fibrillin-1 likely being a substrate for ADAMTS10. The absence of well-defined fibrillin-1 micro- fibrils in cells lacking ADAMTS10 points toward a role for ADAMTS10 in fibrillin-1 assembly or modification doi:10.1016/j.matbio.2006.08.185 163 Skeletal phenotype of mice overexpressing mutant human COMP K. Posey a , Y. Yang b , E.S. Bales a , A. Veerisetty a , R. Haynes c , S.K. Sharan b , J.T. Hecht a,c a Department of Pediatrics, University of Texas Medical School at Houston, Houston, TX 77030, USA b Genetics of Cancer Susceptibility, National Cancer Institute, Frederick, MD 21702, United States c Shriners Hospital for Children, Houston, TX 77030, USA Cartilage oligomeric matrix protein (COMP) is an extra- cellular matrix protein found primarily in cartilage and S67 ASMB Meeting Abstracts / Matrix Biology 25 (2006) S1–S94