FGF is required for posterior neural patterning but not for neural induction

T. Holowacz et S. Sokol, FGF is required for posterior neural patterning but not for neural induction, DEVELOP BIO, 205(2), 1999, pp. 296-308
Citations number
Categorie Soggetti
Cell & Developmental Biology
Journal title
ISSN journal
0012-1606 → ACNP
Year of publication
296 - 308
SICI code
Fibroblast growth factor (FGF) has been implicated in a variety of developm ental processes including posterior mesoderm and neural patterning. Previou s work has led to contradictory roles for FGF in neural induction and anter oposterior neural patterning. Launay et al. (Development 122, 869-880, 1996 ) suggested a requirement for FGF in anterior neural induction. In contrast , Kroll and Amaya (Development 122, 3173-3183, 1996) and Bang et al. (Devel opment 124, 2075-2085, 1997) proposed that FGF is not required for early ne ural patterning. Here we use a loss-of-function assay to examine whether FG F is required for neural patterning in three experimental situations: (i) i n Xenopus early embryos, (ii) in embryonic explants consisting of presumpti ve dorsal mesoderm and neurectoderm (Keller explants), and (iii) in explant s of dorsal ectoderm and posterior mesoderm in which FGF signaling is speci fically blocked in the ectoderm. When cultured until tailbud stages, Keller explants develop neural tissue with normal anteroposterior pattern. Overex pression of the dominant-negative FGF receptor (XFD) in Keller explants inh ibited the posterior neural markers Eu-2, Krox-20, and HoxB9, but not the p anneural marker nrp-1 and the anterior neurectodermal markers XAG-1 and Xot x-2. Similar results were seen in whole embryos, but only when XFD RNA was targeted to both the dorsal and lateral regions. In contrast, addition of F GF to Keller explants resulted in a shift of the midbrain-hindbrain boundar y marker En-2 to a more anterior position normally fated to become cement g land. We also determined whether FGF is required specifically by the neurec toderm for anteroposterior neural patterning. Recombinants of dorsal ectode rm and posterior mesoderm were made in which FGF was specifically blocked i n the ectoderm. Spinal cord and hindbrain markers were inhibited in these r ecombinants, whereas anterior markers and cement gland development were enh anced. Our results demonstrate that FGF is important for posterior developm ent in both mesoderm and neurectoderm and that neural induction and posteri orization represent separable developmental events. (C) 1999 Academic Press .