MORPHOLOGY AND SIGNIFICANCE OF PROGRAMMED CELL-DEATH IN THE DEVELOPING LIMB BUD OF THE VERTEBRATE EMBRYO

Cell death constitutes a basic mechanism accounting for many morphogen etic and histogenetic events during normal and abnormal development of embryonic organs and tissues. This article focuses on the major areas of mesodermal cell death occurring during vertebrate limb development . In early stages of limb development, cell death appears to reduce th e amount of mesodermal tissue destined to form the anlage of the autop odium. In later stages, cell death plays a role sculpturing the shape of the digits. The morphology of the dying cells corresponds with apop tosis, but internucleosomal DNA fragmentation by endonuclease activati on does not appear to be a precocious feature. The cell death program can be inhibited in vivo and in vitro by changing the environmental co nditions of the prospective dying cells up to 6-10 h before death. In this review, we survey possible factors controlling the establishment of the cell death program. Information concerning the biochemical basi s of cell death in the developing limb is also revised. Finally, the p ossible role of genes whose pattern of expression is coincident with t he dying processes is discussed. (C) 1995 Wiley-Liss, Inc.