BMI1 and osteoporosis: In this study, we demonstrated that Bmi-1 deficiency resulted in growth retardation and premature aging because of decreased proliferation and increased apoptosis, decreased ratios and dysmaturity of lymphocytic series, impaired skeletal growth and development and premature osteoporosis associated with decreased osteoblastic bone formation, increased adipocyte formation and up-regulated senescence-associated molecules, and increased oxidative stress and DNA damage of multiple organs.