Shortly after their formation, somites of vertebrate embryos
differentiate along the dorsoventral axis into sclerotome,
myotome and dermomyotome. The dermomyotome is then
patterned along its mediolateral axis into medial, central
and lateral compartments, which contain progenitors of
epaxial muscle, dermis and hypaxial muscle, respectively.
Here, we used Wnt-11 as a molecular marker for the medial
compartment of dermomyotome (the ‘medial lip’) to
demonstrate that BMP in the dorsal neural tube indirectly
induces formation of the medial lip by up-regulating Wnt-1
and Wnt-3a (but not Wnt-4) expression in the neural tube.
Noggin in the dorsal somite may inhibit the direct action of
BMP on this tissue. Wnt-11 induction is antagonized by
Sonic Hedgehog, secreted by the notochord and the floor
plate. Together, our results show that the coordinated
actions of the dorsal neural tube (via BMP and Wnts), the
ventral neural tube/notochord (via Shh) and the somite
itself (via noggin) mediates patterning of the dorsal compartment of the somite
