Surprisingly, the knowledge about the status of TGF-β pathway activation in OI patients is quite scarce, although some evidences, such as an increased expression of TGF-β receptors in human OI osteoblasts, point also to an increased TGF-β signaling in OI patients (Gebken et al., 2000). The gene discussed is TGFB1; the disease is osteogenesis imperfecta.