MOUSE CATHEPSIN-K - CDNA CLOSING AND PREDOMINANT EXPRESSION OF THE GENE IN OSTEOCLASTS, AND IN SOME HYPERTROPHYING CHONDROCYTES DURING MOUSE DEVELOPMENT

We have constructed cDNA clones covering the entire coding region of m ouse, human and rabbit preprocathepsin It mRNA for studies on bone tur nover, The clone pMCatK-1 for mouse cathepsin K shares 87% nucleotide homology with the corresponding human and rabbit sequences, Analysis o f a panel of mouse tissues for tissue distribution of cathepsin K mRNA revealed the highest levels in musculoskeletal tissues: bone, cartila ge and skeletal muscle, In situ hybridization of developing mouse embr yos was performed to identify the cellular source of cathepsin K mRNA, The strongest mRNA signal was detected in osteoclasts of bone, identi fied in serial sections by positive TRAP staining, Cathepsin K mRNA wa s also observed in some hypertrophic chondrocytes of growth cartilages . Association of cathepsin K production with degradation of bone and c artilage matrix suggests that this enzyme and its mRNA levels could se rve as markers for matrix degradation in diseases affecting these tiss ues.