CRTAP and osteogenesis imperfecta: Autosomal dominant mutations of COL1 in humans cause osteogenesis imperfecta (OI; MIM #259420), a bone dysplasia characterized by bone deformities, low bone mass, poor bone quality, frequent fractures, and high non-union rate (Table 2).235 Cartilage-associated protein (CRTAP) catalyzes the maturation of COL1 by 3-hydroxylation, and its mutations also cause OI.