Indeed, osteoprotegerin is not induced in Notch3em1Ecan mice explaining their RANKL-dependent resorptive phenotype, is induced in RosaNotch3 bone marrow stromal cells, possibly explaining the gain in cancellous bone, and is suppressed in RosaNotch3 osteocytes possibly explaining the cortical bone porosity and osteopenia of mice overexpressing NOTCH3-NICD. This evidence concerns the gene TNFRSF11B and Osteopenia.