Fig. 1.

Components of the posttranslational modification machinery of type I collagen causing osteogenesis imperfecta and Bruck syndrome. Figure depicts proteins involved in posttranslational modification of type I collagen and mutated in osteogenesis imperfecta (OI) or Bruck syndrome. Mutations in genes (COL1A1 and COL1A2) encoding the α₁ and α₂ chains of type I procollagen most commonly result in dominant OI and rarely recessive OI. Other rare causes of recessive OI have been shown to be caused by mutations in genes encoding the CRTAP/P3H1/cyclophilin B or SERPINH1/FKBP10 protein complexes. These proteins modify collagen by 3-prolyl-hydroxylation and serve as endoplasmic reticulum chaperones, respectively. Bruck syndrome is also caused by mutations in genes coding for proteins involved in posttranslational modification of collagen, specifically lysyl hydroxylation. The figure was produced using Servier Medical Art: http://www.servier.com/Smart/ImageBank.aspx?id_=729.