TCF4 and osteogenesis imperfecta: Intriguingly, the bone tissues obtained from DKK1-AS treated OI mice exhibited markedly heightened β-catenin and TCF4 immunoreactivities in comparison to the bone tissue from both untreated and DKK1-S treated OI mice (p < 0.001 for both β-catenin and TCF4) (Figs. 8, 9).