In zebrafish, the frilly fins (frf) mutant harbors mutations in bmp1a (Asharani et al., 2012) and exhibits high vertebral bone mineral density (BMD) in adults, mimicking the high BMD phenotype in humans with OI caused by BMP1 mutations (Asharani et al., 2012). Here, BMP1 is linked to osteogenesis imperfecta.