Our new understanding of how the TGF-β1 mutation-triggered overactivation of Rho GTPases in CED leads to high bone turnover will help address the specific mechanisms of decreased bone density or osteoporosis due to aberrant TGF-β1 signaling in related diseases and inform the development of new therapeutic approaches. The gene discussed is TGFB1; the disease is cranioectodermal dysplasia.