Elsevier

Developmental Biology

Volume 205, Issue 2, 15 January 1999, Pages 296-308
Developmental Biology

Regular Article
FGF Is Required for Posterior Neural Patterning but Not for Neural Induction

https://doi.org/10.1006/dbio.1998.9108Get rights and content
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Abstract

Fibroblast growth factor (FGF) has been implicated in a variety of developmental processes including posterior mesoderm and neural patterning. Previous work has led to contradictory roles for FGF in neural induction and anteroposterior neural patterning. Launayet al.(Development122, 869–880, 1996) suggested a requirement for FGF in anterior neural induction. In contrast, Kroll and Amaya (Development122, 3173–3183, 1996) and Banget al.(Development124, 2075–2085, 1997) proposed that FGF is not required for early neural patterning. Here we use a loss-of-function assay to examine whether FGF is required for neural patterning in three experimental situations: (i) inXenopusearly embryos, (ii) in embryonic explants consisting of presumptive dorsal mesoderm and neurectoderm (Keller explants), and (iii) in explants of dorsal ectoderm and posterior mesoderm in which FGF signaling is specifically blocked in the ectoderm. When cultured until tailbud stages, Keller explants develop neural tissue with normal anteroposterior pattern. Overexpression of the dominant-negative FGF receptor (XFD) in Keller explants inhibited the posterior neural markers En-2, Krox-20, and HoxB9, but not the panneural marker nrp-1 and the anterior neurectodermal markers XAG-1 and Xotx-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 FGF to Keller explants resulted in a shift of the midbrain–hindbrain boundary marker En-2 to a more anterior position normally fated to become cement gland. We also determined whether FGF is required specifically by the neurectoderm for anteroposterior neural patterning. Recombinants of dorsal ectoderm and posterior mesoderm were made in which FGF was specifically blocked in the ectoderm. Spinal cord and hindbrain markers were inhibited in these recombinants, whereas anterior markers and cement gland development were enhanced. Our results demonstrate that FGF is important for posterior development in both mesoderm and neurectoderm and that neural induction and posteriorization represent separable developmental events.

Keywords

anteroposterior axis
gastrulation
fibroblast growth factor
Xenopus.

Cited by (0)

B. K. KayH. B. Peng

1

Present address: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Ave., Boston, MA 02115. E-mail:[email protected].

2

To whom correspondence should be addressed. E-mail:[email protected].