CRTAP and osteogenesis imperfecta type 7: He Xu et al., showed mice deficient in crtap, a cartilage-associated protein that is associated with post-translational modification of Type I collagen, as well as mice with osteogenesis imperfecta Type VII due to loss of Col1a2 (oim) have less alveolar bone and dentin volume and greater PDL volume [27].