This observation confirms previous findings from others, showing that type I collagen expression levels are very similar in osteoblasts and osteocytes39 and that Col1a1 is expressed at even higher levels in osteocytes compared with osteoblasts during the early anabolic response to a sclerostin antibody in a rat model.52 We show here that type I collagen expression is significantly upregulated in both mouse models of OI (together with Bglap and Sparc), suggesting perhaps a futile attempt to increase bone formation. Here, COL1A1 is linked to osteogenesis imperfecta.