Extrinsic influences on limb muscle organisation

Skeletal muscle within the vertebrate limb originates from the somite. Much work has focussed upon the role of secreted signalling molecules of the He dgehog, fibroblast growth factor (FGF), bone morphogenetic protein (BMP), a nd Wnt families plus their associated antagonists in establishing semitic c ell types, yet there is no consensus on how these signals combine to influe nce muscle patterning. When semitic cells migrate into the limb bud, they b ecome subject to a new set of guidance and patterning cues. Here we discuss the possible roles played by signalling proteins, particularly Hedgehogs, in guiding the cells of the limb musculature to their fate.