COL1A2 and osteogenesis imperfecta: In classical OI types I-IV, which represents 85-90% of OI cases, inherited AD mutations occur in genes COL1A1 and COL1A2, which encode proteins used to assemble type I collagen (Palomo et al. 2017; Etich et al. 2020; Valadares et al. 2014).