Several advances have been made in our understanding of the control of the
growth and patterning of embryonic limbs. Development of the vertebrate lim
b is dependent on reciprocal interactions between the ectoderm and mesoderm
that regulate the structure and function of the apical ectodermal ridge. O
ne key component of this regulatory program appears to be the precise contr
ol of signaling by members of the bone morphogenetic protein family via mul
tiple antagonistic interactions.