WNT1 and osteogenesis imperfecta: Similarly, the Wnt1-cKO in MSCs [212] and the Wnt1-cKO in late osteoblasts and osteocytes [212] also recapitulate the OI phenotype, with impaired osteoblast activity, decreased mineralization and bone formation rate and spontaneous fractures, the latter displaying a milder phenotype, with conserved osteoblast and osteoclast numbers [207,212] (Table 3).