P4HB and osteogenesis imperfecta: Up to now, at least 20casuative genes of OI have been identified, including COL1A1, COL1A2,IFITM5, CRTAP, LEPRE1, FKBP10, PLOD2, PPIB, SERPINF1, SERPINH1, SP7, WNT1, BMP1,TMEM38B, PLS3, CREB3L1, SEC24D, SPARC, P4HB, andMBTPS2, which are involved in encoding or post-translationalmodification process of type I collagen or regulating osteoblasts function [4–9].