Because the expression of the mutant MALEP BRIL in OI type V has been proposed as a gain-of-function, we next compared the ability of the wild type (WT) BRIL and its mutant MALEP form at inducing the MEF2-Luc and NFATc-Luc reporters in MC3T3-E1 (Figure 2). Here, IFITM5 is linked to osteogenesis imperfecta type 5.