The Bmp pathway in skull vault development.

The Bmp pathway is of critical importance in the development of the skull vault. Analysis of gain and loss of function phenotypes of Bmp pathway effectors, particularly Msx genes, has shown that the Bmp pathway functions in the growth of both mesodermal and neural crest-derived calvarial bones. It is required for the development of the frontal and parietal bones during the interval between the initial osteogenic mesenchymal condensations at E12.5 to the apposition of the paired frontal and parietal bones at E18.5. During postnatal development, forced expression of the Bmp inhibitor, noggin, maintains the patency of sutures, consistent with a role for the Bmp pathway in regulating suture development. The availability of conditional mutants of Bmp ligands, receptors and downstream effectors will make possible an increasingly high resolution analysis of precisely how the Bmp functions in these processes and how aberrations in its activity can contribute to pathological conditions such as familial parietal foramina and craniosynostosis.