Ultrastructural Organisation of Cartilage in Proteoglycan-Deficient Zebrafish Mutants
M Wiweger, C Avramut, F Prins, RBG Ravelli, PCW Hogendoorn. LUMC, Leiden, Netherlands
Background: Proteoglycans (PGs) are molecules consisting of a protein core onto which sugar chains, glycosaminoglycans (GAGs), are attached. PGs are produced by chondrocytes and, once secreted, they become a major component of the extracellular cell matrix (ECM). PGs and ECM are involved in many cellular events such as adhesion, migration and differentiation. Changes in PG structure and composition were found in various pathologies, e.g. osteochondromas and osteoarthritis. In order to investigate the role of different PGs in cartilage development, we studied a group of zebrafish (Danio rerio) mutants affected in different genes involved in PG-synthesis.
Design: We used AB (wild type) zebrafish and five mutant lines: dak (ext2), which lacks Heparan sulphate only; hi307 (β3gat3) that is deficient in both Heparan and Chondroitin sulphates; pic (papst1), which is unable to sulfate PGs; hi954 (uxs1) that fails to initiate GAG biosynthesis and kny (gpc4) that does not form the protein core of Glypican 4. WT and homozygous mutants were raised till 5dpf under standard conditions, anesthetized in tricane and fixed in glutaraldehyde. Light microscopy observations were performed on five fish from each line. Single representatives of each line were also subjected to the electron microscopy.
Results: Our results show that each mutant displayed a different phenotype. For example, chondrocytes in the β3gat3 mutant displayed a WT morphology, while the ones from the uxs1 mutant were enlarged, misshapen and partially fused with each others (Pic. 1). However, all mutants had abnormal ECM and/or chondrocyte morphology. For instance, the β3gat3 mutant lacked collagen network, whereas the uxs1 mutant had bundles of short and very thick collagen fibers. The association of PG aggregates with collagen network was also disrupted to a different extend in each of the mutants we studied.
Conclusions: PGs have different influence on the chondrocyte morphology and the organization of the collagen network in ECM. In consequence, water-binding capacity and mechanical properties of cartilage could be altered by changes in the quality and quantity of the different PGs.
Category: Bone & Soft Tissue
Tuesday, March 23, 2010 9:30 AM
Poster Session III # 30, Tuesday Morning