Conditional expression of mutant Ifitm5 in the Rosa26mIfitm5 Prx1-Cre and Rosa26mIfitm5 Acan-Cre ERT2 mice resulted in a low bone mass phenotype, as seen in individuals with OI type V. Biomechanical testing in the Rosa26mIfitm5 Acan-Cre ERT2 model demonstrated reduced ductility and increased bone stiffness, correlating with the findings in other OI mouse models (55, 56). This evidence concerns the gene MAPK3 and osteogenesis imperfecta type 5.