COL1A1 and osteogenesis imperfecta: Osteogenesis imperfecta type I is characterized by thepresenceof a defect in the COL1A1 gene, which leads toa decrease in the amount of type I collagen produced; intypes II–IV, due to mutations in the COL1A1 and COL1A2genes, type V is due to mutations in the IFITM5 gene anddysregulation of bone mineralization, type VI occurs due toa mutation in the SERPINF1 gene, which leads to a defect inbone mineralization; types VII (CRTAP gene), VIII (LEPRE1 gene, also known as P3H1) and IX (PPIB gene) are the resultof a defect in the collagen 3-hydroxylation process.