Low bone density and bone fragility are the hallmarks of osteogenesis imperfecta (OI), a heterogeneous group of heritable bone disorders often caused by a mutation affecting one of the two genes COL1A1 and COL1A2 that encode collagen type I chains (Rauch and Glorieux, 2004; van Dijk et al., 2011). Here, COL1A1 is linked to osteogenesis imperfecta.