WRN and Werner syndrome: To test this hypothesis and to evaluate the physiological similarity of osteoporosis in Terc−/− mice (telomerase mutants; a model for dyskeratosis congenita), Wrn−/− mice (a model for Werner’s syndrome), Terc−/−Wrn−/− double-mutant mice and the human condition, the authors evaluate the skeletal phenotypes of the mutant mice.