INTRODUCTION The fibroblast growth factor (FGF) family is composed of a number of heparin-binding proteins characterized by their potent mitogenic effects on cells, their ability to promote migration and differentiation, and to induce angiogenesis

The fibroblast growth factor (FGF) family is composed of a number of heparin-binding proteins characterized by their potent mitogenic effects on cells, their ability to promote migration and differentiation, and to induce angiogenesis (reviewed by Folkman and Klagsbrun, 1987; Gospodarowicz, 1988). FGF has also been implicated in the regulation of vertebrate development. Mesoderm-inducing activity by basic FGF (bFGF) has been demonstrated in early Xenopus embryos, and FGF mRNA transcripts, FGF-like proteins and FGF-receptors, were described in this system (Kimelman and Kirschner, 1987; Slack et al., 1987; Kimelman et al., 1988; Gillespie et al., 1989; Slack and Isaacs, 1989). Other members of the FGF family have also been identified in association with developmental processes. Represa et al. (1991) implicated the int-2 proto-oncogene, which encodes several FGF-like proteins, in the induction of the otic vesicle of the chick. In mammals, evidence of a role for FGF in pattern specification is less direct, although the differential expression of bFGF, acidic FGF (aFGF) and FGF-5 genes during the latter half of embryonic development in the mouse certainly suggests such a function (Hébert et al., 1990). A role for FGF in the growth and maintenance of skin cells was indicated when epidermal keratinocytes and dermal fibroblasts were found to proliferate in response to both aFGF and bFGF in vitro (O’Keefe et al., 1988; Ristow and Messmer, 1988; Shipley et al., 1989; Pisansarakit et al., 1991). In the sheep, aFGF was found to be more mitogenic than bFGF for skin keratinocytes (Pisansarakit et al., 1990). Basic FGF has also been detected in cultured fibroblasts (Story, 1989; Pisansarakit et al., 1991) and human keratinocytes (Halaban et al., 1988), and a bFGF-like pep667 Journal of Cell Science 105, 667-674 (1993) Printed in Great Britain © The Company of Biologists Limited 1993