KLF10 knock-out (KO) mice have slow osteoblast production of RANKL (receptor activator of nuclear factor kappa-B ligand) and high levels of osteoprotegerin (OPG), which delays OCL differentiation, leading to a reduced bone turnover and a loss of bone (osteopenia) [34,35,46]. The gene discussed is KLF10; the disease is Osteopenia.