Parathyroid hormone (PTH) plays a critical role in the regulation of chondrogenesis. In this study, we have found for the first time that Runt-related transcription factor 1 (Runx1) contributes to PTH-induced chondrogenesis. Upon PTH treatment, limb bud mesenchymal progenitor cells in micromass culture showed an enhanced chondrogenesis, which was associated with a significant increase of chondr...

The relationship between cellular position and growth control has been studied in cultures of dissociated fragments of mouse limb bud cells. Using cells derived from various positions along the anterior-posterior axis of the limb bud we have developed culture conditions that optimize growth of positionally isolated cells. Under these conditions limb bud cells display an inherent, position-speci...

Fibroblast growth factors (FGFs) act as signals in the developing limb and can maintain proliferation of limb bud mesenchyme cells. Remarkably, beads soaked in FGF-1, FGF-2, or FGF-4 and placed in the presumptive flank of chick embryos induce formation of ectopic limb buds, which can develop into complete limbs. The entire flank can produce additional limbs, but generally wings are formed anter...

Two regions of the chick limb bud--the apical ectodermal ridge and the zone of polarizing activity--have been shown to influence cell division and pattern formation during normal development and following surgical manipulation. In this study, using a simple coculture system, together with autoradiography, we have shown that these morphogenetically active regions of the limb bud can stimulate qu...

Mutations that affect vertebrate limb development provide insight into pattern formation, evolutionary biology and human birth defects. Patterning of the limb axes depends on several interacting signaling centers; one of these, the zone of polarizing activity (ZPA), comprises a group of mesenchymal cells along the posterior aspect of the limb bud that express sonic hedgehog (Shh) and plays a ke...

Embryonic chick wing bud tissues secrete diffusible mitogens when cultured in vitro (Bell & McLachlan, 1985). These molecules may play an important role in limb development since media conditioned by morphogenetically active regions of the wing bud possess greater mitogenic activity than media conditioned by non-morphogenetic regions. These studies show that while the chick-derived growth facto...

Myogenic cells migrate into the limb from the somitic mesoderm, taking up positions in the dorsal and ventral compartments before differentiating into the limb musculature. This process is influenced by the tissues of the limb in a number of ways. Cells of the lateral part of the somitic dermomyotome are induced to express a migratory myogenic phenotype by a diffusible signal originating in the...

The transcription factor Sox9 is expressed in all chondroprogenitors and has an essential role in chondrogenesis. Sox9 is also expressed in other tissues, including central nervous system, neural crest, intestine, pancreas, testis, and endocardial cushions, and plays a crucial role in cell proliferation and differentiation in several of these tissues. To determine the cell fate of Sox9-expressi...

An analysis has been made of the pre-cartilaginous condensation stage in the development of the femur and tibia/fibula skeletal blastemata of the embryonic chick hind limb. Light microscopy serial sections were used to 'map' the mesenchymal cell condensations of both myogenic and chondrogenic anlagen in the limb-bud from stages 22 to 26 (Hamburger & Hamilton, 1951). Cell counts reveal that an i...