The inducible Ifitm5flox c.-14C>T mouse model and integrated single-cell transcriptomic analyses elucidated that ectopic expression of SOX9 and disrupted homeostatic balance among osteogenesis, chondrogenesis, and adipogenesis may contribute to the pathogenesis caused by MALEP-IFITM5, helping to gain deeper insights into the molecular mechanisms of type V OI. This evidence concerns the gene SOX9 and osteogenesis imperfecta type 5.