SERPINH1 and osteogenesis imperfecta: Mutations in Hsp47 and consequent impairment of the chaperone function in the ER, lead to overhydroxylation and partial intracellular retention of procollagen I. Both consequences, ER stress and aberrant bone collagen crosslinking, underlie the OI pathology associated to crosslinking defects, but further studies are required [159].