DISTRIBUTION OF FGF-2 SUGGESTS IT HAS A ROLE IN CHICK LIMB BUD GROWTH

We developed and characterized antibodies specific for FGF-2 and used them to locate FGF-2 during chick embryo development. A series of micr ographs demonstrated the progression of FGF-S staining during developm ent of the different tissues and organs. FGF-2 was present in the ecto derm covering the entire embryo, muscle cells, nervous system, neural crest cells, and mesonephros. FGF-2 was also present in the limb from initiation of budding through differentiation. The limb ectoderm and s ubjacent mesoderm showed the strongest immunostaining, with lower leve ls in the center of the bud. However, the distribution of FGF-2 positi ve cells in the mesoderm was not homogeneous. This heterogeneity was n ot due to cell cycle specific distribution of FGF-2 protein, as flow c ytometric analysis showed that FGF-2-positive cells were distributed t hroughout the cell cycle. However, the amount of anti-FGF-2 fluorescen ce varied most during G1, consistent with the possibility that FGF-2 i s low after M phase and increases during G1. A bioassay was used to de monstrate FGF-S levels in the wing ectoderm were approximately 2.7-fol d greater than in the mesoderm. We propose that the location of FGF-2 in the embryo is consistent with a role in epithelial-mesenchymal inte ractions; in the limb bud it may prevent differentiation and permit li mb outgrowth and subsequent expression of patterning events. (C) 1993 Wiley-Liss, Inc.