A. Deletion of Capns1 in cells of the osteoblast lineage showed reduced trabecular bone in primary spongiosa of proximal tibias. Mutant trabecular bone displayed reduced TRAP mRNA expression and reduced number of cells stained with TRAP. H&E; hematoxylin and eosin staining. B-G. Osteoblast-specific Capns1 knockout mice were resistant to a low calcium diet-induced bone resorption. μCT analysis was performed on femoral bone samples isolated from 13-week old control and mutant mice either on a normal chow or a low calcium diet for 4 weeks. BV/TV, bone volume/ total volume; Tb. N., trabecular number; Tb. Th., trabecular thickness; Cortical Th., cortical thickness; and pMOI, polar moments of inertia. A normal diet; control (n=9) vs. mutant (n=9): A high fat diet; control (n=11) vs. mutant (n=12). *p<0.05.