Recent molecular advances in understanding vertebrate limb development.

Considerable recent advances have been made in understanding the mechanisms of vertebrate limb development. New information about molecules governing cell interactions in embryonic limbs begins to bridge the gap between the experimental analysis and genetics of congenital limb defects. There are four main stages in vertebrate limb development: initiation, specification of limb pattern, tissue formation accompanied by limb morphogenesis, and growth. Although classical embryology focused on chick embryos and recent molecular analysis centres on limbs of both chickens and mice, most of the fundamental mechanisms that have been uncovered appear to be conserved between vertebrates and are likely to be directly applicable to human limb development.