Development of the limb neuromuscular system

Appendages, such as wings of a fly or limbs of a vertebrate, are excellent models to study the principles of patterning and morphogenesis. In the adul t these structures are used for a variety of behaviors, including locomotio n. Although support structures of the adult vertebrate limb are generated w ithin the limb bud, its dynamic elements are derived from the semitic mesod erm and neural tube. Recent studies show that regional patterns set up in t he mesenchyme-filled limb bud guide muscle precursors and developing motor axons to their proper location within the limb. Subsequent development of t he neuromuscular system is regulated by cell surface interactions between p re-specified muscle fibers and motor axons.