XB-ART-21566Cell February 25, 1994; 76 (4): 761-75.
Floor plate and motor neuron induction by vhh-1, a vertebrate homolog of hedgehog expressed by the notochord.
The differentiation of distinct cell types in the ventral neural tube depends on local inductive signals from the notochord. We have isolated a vertebrate homolog of the Drosophila segment polarity gene hedgehog (hh) from zebrafish and rat, termed vhh-1. vhh-1 is expressed in the node, notochord, floor plate, and posterior limb bud mesenchyme. Each of these cell groups has floor plate inducing activity, suggesting that the vhh-1 gene may encode a floor plate-inducing molecule. Widespread expression of rat vhh-1 in frog embryos leads to ectopic floor plate differentiation in the neural tube. In vitro tests for the signaling functions of vhh-1 demonstrate that COS cells expressing the rat vhh-1 gene induce floor plate and motor neuron differentiation in neural plate explants. vhh-1 may, therefore, contribute to the floor plate and motor neuron inducing activities of the notochord.
PubMed ID: 8124714
Article link: Cell
Species referenced: Xenopus laevis
Genes referenced: foxa2 shh spon1
Article Images: [+] show captions
|Figure 3. Ectopic Expression of F-Spondin and HNF-3B in the Dorsal Neural Tube of Frog Embryos Injected with a Plasmid Expressing Rat vhh-l (A) Cross section of neurula stage (approximately stage 16) Xenopus embryo expressing rat v/#/?-l mRNA from a plasmid driven by a CMV promoter. The rat vhh-l gene is detected predominantly in one half of the neural plate. Lateral arrows denote the lateral extent of the neural plate. Abbreviations: np, neural plate; n, notochord; s, somite. (B and C) Lateral views of tadpole stage (approximately stage 34) embryos showing the pattern of F-spondin mRNA expreaskin in an embryo injected with CMV antisense vhh-7 plasmid (B) and CMV sense vM-7 plasmid (C). F-spondin is expressed in the floor plate (fp) at the ventral midline of the neural tubs and in the hypochord (h) located ventral to the notochord (n). Ectopic expression of F-spondin mRNA is detected in the dorsal neural tube in (C) and in the dorsal ventricular zone adjacent to the Root plate (first and last arrowheeds in [CD (see aleo Ruit i Altaba et al., 1993a; data not shown). Ectopic F-spondin expression occurs in the po&srior hindbrain and in the spinal cord. (D-l) Cross sections of tadpole stage (approximately stages 32-36) embryos injsctad with CMV antisense vhh-I (D and G) or sense I&-7 (E, F, H, and I) plasmids showing the expression of F-spondin mRNA (D-F) or HNF-3@ protein (G-l). (D-F) Embryos injected with CMV antisense vhh-I plasmids show a normal peltern of F+pondin mRNA expme&m, r~tothefbarplate (fp in [D]). Ectopic expression of F-spondin in embryc6 injected with a CMV sense v&l plasmid is detected in roof plate oaks of the hindbrain (E) and spinal cord (F). (G-l) Embryos injected with a CMV antisense vhh-7 plasmid show the normal pattern of HNFa protein expre&on, met&ted to the fkor plate (fp in [G]). Ectopic expression of HNFq protein in the rwf plate of the hindbrain (H) and spinal cord (I) is detected in embryos expmaaing vhh-I. Ectopic expression of these floor plate markers was also detected in the dorsal midbrain (data nol shown). HNF-3fJ expression is also detected at very low levels in the notochord (n in [I]). Scale bars are 10 urn in (A) and (D-l) and 200 pm in (B) and (C).|