Correlation of clinical phenotype and COMP trafficking

Correlation of clinical phenotype and COMP trafficking

S64 ASMB Meeting Abstracts / Matrix Biology 25 (2006) S1–S94 lymphocytes. Surviving subsets of Tg and KO mice likewise presented an altered lymphocy...

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S64

ASMB Meeting Abstracts / Matrix Biology 25 (2006) S1–S94

lymphocytes. Surviving subsets of Tg and KO mice likewise presented an altered lymphocyte profile in marrows and lymphatics throughout life. Moreover, all collagen X mice displayed altered serum and growth plate cytokine expression by ELISA, RT-PCR, and protein array. We propose a cytokine metabolism imbalance, linked to an impaired HC matrix, as a cause of hematopoietic defects in the collagen X mice. (DK057904 to OJ). doi:10.1016/j.matbio.2006.08.175

153 Prolyl 3-hydroxylation and recessive osteogenesis imperfecta R. Morello a, T. Bertin a, J. Hicks b, P. Castagnola c, F.H. Glorieux d, H. Bachinger e, P.H. Byers f, D.R. Eyre f, B.F. Boyce g, B. Lee h a

Baylor College of Medicine, Houston, TX, United States Texas Children's Hospital, Houston, TX, United States c Istituto Nazionale Ricerca sul Cancro, Genova, Italy d Shriners Hospital for Children, Montreal, Canada e Shriners Hospital for Children, Portland, OR, United States f University of Washington, Seattle, WA, United States g University of Rochester Medical Center, Rochester, NY, United States h Howard Hughes Medical Institute, Houston, TX, United States b

The biological consequences of collagen prolyl 3-hydroxylation are unknown. We previously identified a novel protein, CRTAP that was expressed during chondrogenesis. Crtap null mice show an osteochondrodysplasia characterized by rhizomelia, kyphosis, and severe osteopenia. Histomorphometric analyses showed normal numbers of osteoblasts and osteoclasts but significantly decreased bone mass and bone formation rate, with very little osteoid and a decreased mineralization lag time. Our data show that the low bone mass is due to decreased osteoid formation, but with an accelerated matrix mineralization. CRTAP can complex with prolyl 3-hydroxylase 1 protein and Crtap−/− mice lack fibrillar collagen prolyl 3-hydroxylation. On EM, collagen fibrils appear thickened suggesting a defect in fibrillogenesis. Finally, we identified CRTAP mutations in two families with recessively inherited forms of OI. In the original family with OI type VII, we detected a C>G transversion in intron 1 that created a new splice donor site and activated a cryptic exon. In the second, a single nucleotide deletion in exon 4 led to a frameshift and lack of mRNA and protein. Our data demonstrate the importance of prolyl 3-hydroxylation for bone formation, collagen fibrillogenesis and osteoid synthesis, and that loss of function of CRTAP causes recessive OI. doi:10.1016/j.matbio.2006.08.176

154 Correlation of clinical phenotype and COMP trafficking K.L. Posey a, T. Chen b, E.S. Bales a, J. Hecht

a,c

, B. Vertel

a

a

Department of Pediatrics, University of Texas Medical School at Houston, Houston, TX 77030, USA b Department of Cell Biology and Anatomy, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA c Shriners Hospital for Children, Houston, TX 77030, USA Mutations in cartilage oligomeric matrix protein (COMP) produce clinical phenotypes ranging from pseudoachondroplasia (PSACH), a dwarfing condition, to a mild condition, multiple epiphyseal dysplasia (MED/EDM1). It has been difficult to determine why different mutations give rise to the variable clinical phenotype since chondrocytes from both PSACH and EDM1 have dialated rER containing COMP. The most common PSACH mutation severely impedes cellular trafficking of COMP and type IX collagen, consistent with observations from patient cells. We hypothesized that PSACH and EDM1 mutations variably affect the cellular trafficking behavior of COMP and this correlates with the clinical severity. FLAG-tagged mutant COMP proteins with 11 different mutations were expressed in RCS cells and the relative COMP protein retention was assessed. Mutations in type 3 repeat domain correlated with clinical phenotype; the PSACH mutations having more cells retaining mutant COMP, while EDM1 mutations were associated with fewer cells containing rER-retained protein. In contrast, the cellular trafficking pattern observed for the mutations in the C-terminal globular domain was not predictive of the clinical phenotype. These results clearly demonstrate that different COMP mutations do have variable effects on the intracellular transport system. doi:10.1016/j.matbio.2006.08.177

155 A spectrum of dominant collagen VI mutations in Bethlem myopathy N.L. Baker a, M. Mörgelin b, R.A. Pace a, N.E. Adams a, J.F. Bateman a, S.R. Lamandé a a

Murdoch Childrens Research Institute and University of Melbourne, Parkville 3052, Australia b Lund University, Lund, Sweden Collagen VI is an abundant ECM protein made up of three subunits encoded by COL6A1, COL6A2 and COL6A3. Mutations in these genes cause Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD). BM is a