Bone morphogenetic protein-4 expression in the adult rat brain

Bone morphogenetic protein-4 (BMP4) is a member of the transforming growth factor-beta (TGF-beta) superfamily and plays important roles in multiple biological events. Although BMP4 expression has been well described in the early development of the central nervous system (CNS), little information is available on its expression in the adult CNS. Therefore, we investigated BMP4 expression in the adult rat CNS by using immunohistochemistry. BMP4 is intensely expressed in most neurons and their dendrites. In addition, intense BMP4 expression was also observed in the neuropil of the gray matters where high plasticity is reported, such as the molecular layer of the cerebellum and the superficial layer of the superior colliculus. Furthermore, we found that astrocytes also express BMP4 protein. These data indicate that BMP4 is more widely expressed throughout the adult CNS than previously reported, and its continued abundant expression in the adult brain strongly supports the idea that BMP4 plays pivotal roles also in the adult brain.