Retention of cartilage oligomeric matrix protein (COMP) and cell death in redifferentiated pseudoachondroplasia chondrocytes

Cartilage oligomeric matrix protein (COMP) is a large extracellular glycoprotein that is found in the territorial matrix surrounding chondrocytes. Two skeletal dysplasias, pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (EDM1) are caused by mutations in the calcium binding domains of COMP. In this study, we identified two PSACH mutations and assessed the effect of these mutations on redifferentiated chondrocyte structure and function. We confirmed, in vitro, that COMP is retained in enormous cisternae of the rough endoplasmic reticulum (rER) and relatively absent in the PSACH matrix. The rER accumulation may compromise chondrocyte function, leading to chondrocyte death. Moreover, while COMP appears to be deficient in the PSACH matrix, the matrix appeared to be normal but the over-all quantity was reduced. These results suggest that the abnormality in linear growth in PSACH may result from decreased chondrocyte numbers which would also affect the amount of matrix produced.     

Résultats préliminaires des sites subfossiles d’Antsingiavo (Madagascar)

Preliminary report on Antsingiavo subfossils sites (Madagascar). Two new sites, Antsingiavo A & B, have been discovered in the Narinda peninsula, situated in the North-West of Madagascar, Province of Mahajanga. Breccias contain microfauna associated with subfossil lemurs of an average size (Archaeolemur) and small (Microcebus). Until now, the subfossil microfauna of Madagascar was practically unknown. The sample from Antsingiavo offers information on past environments in the Narinda peninsula. The new discoveries contribute to an understanding of the diversity Archaeolemur, with different forms in the different areas of Madagascar. To cite this article : D. Gommery et al., C. R. Palevol 2 (2003).