COL1A2 and osteogenesis imperfecta: In addition to the confirmed OI-related collagen genes (COL1A1 and COL1A2), in the past decade, a series of studies have found that a set of new non-collagen gene defects affect normal post-translational processing, molecular folding of type I collagen, fibril formation, osteoblast differentiation, and mineralization, leading to rare autosomal recessive, dominant, and X-linked forms of OI (Bregou Bourgeois et al., 2016; Lindert et al., 2016; Marom et al., 2016; Marini et al., 2017).