P3H1 and osteogenesis imperfecta: ER enlargement was observed in α2(I)-G610C mouse OI models (28) and zebrafish OI models (19) as well as in mouse Aga2 models (26), consistent with the observation in human dermal fibroblasts with a glycine substitution mutation in type I collagen (21) and a variant in prolyl-3-hydroxylase 1 (P3H1), cartilage-associated protein (CRTAP), and cyclophilin B (CyPB) (20).