Nakamura T et al. (1996), Cloning and expression of Xenopus HGF-like prot...

XB-ART-17959

Biochem Biophys Res Commun 1996 Jul 16;2242:564-73. doi: 10.1006/bbrc.1996.1065.

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Cloning and expression of Xenopus HGF-like protein (HLP) and Ron/HLP receptor implicate their involvement in early neural development.

Nakamura T , Aoki S , Takahashi T , Matsumoto K , Kiyohara T , Nakamura T .

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HGF-like protein (HLP), also known as macrophage stimulating protein, is a ligand for Ron receptor tyrosine kinase, a member of the c-Met/hepatocyte growth factor receptor family. We cloned a Xenopus homologue of the Ron/HLP receptor (Xron) and HLP (Xhlp) and analyzed temporal and spatial expressions. Both Xron and Xhlp mRNA were detected in Xenopus embryos at the cleavage stage, as maternally pooled RNA. Zygotic expression of Xron mRNA was seen in early embryos during midblastula and neurula (stage 22), while Xhlp was evident during midblastula and early tadpole (stage 40). Xron mRNA was localized in the most frontal region of the neural fold and peripheral regions of the neural plate, while Xhlp mRNA was seen in midline of the neural plate (notoplate) and the most frontal regions of the neural fold in early neurula. Thus, functional coupling between Ron receptor tyrosine kinase and HLP may have an important role in development of embryonic neural tissue in Xenopus laevis.

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Species referenced: Xenopus laevis
Genes referenced: hap1 hgf mst1 mst1r

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	FIG. 1. Nucleotide sequence of the Xron cDNA and its putative amino acid sequence. The amino acid sequence is shown underneath the nucleotide sequence. The last amino acids of each line are numbered (every 40 residues) starting from the putative initiator methionine at 1. The stop codon is indicated by an asterisk. The last nucleotides of each line are also numbered. The putative signal peptide coding region is underlined. The putative cleavage site and transmembrane domain are indicated by dark boxes. Cysteine residues are boxed. The tyrosine kinase domain is indicated by arrows.
	FIG. 2. Alignment of amino acid sequence of Xenopus Ron, chick c-Sea, and human Ron. Identical amino acids in chick c-Sea and human Ron to those of Xenopus Ron are indicated by dashes in their respective sequences. Cysteine residues conserved in Xenopus Ron, chick c-Sea, and human Ron are boxed.
	FIG. 3. Schematic representation of composition of cysteine residues in the extracellular region of c-Met families. Cysteine residues are indicated by bars. The tyrosine kinase domain is indicated by open boxes.
	FIG. 4. Temporal expression patterns of Xron and its putative ligand Xhlp during Xenopus embryonic development. The expressions of Xron and Xhlp transcripts in total RNAs from Xenopus embryos at the serial developmental stages were analyzed by northern blot hybridization. The Xenopus laevis developmental stages are according to Nieuwkoop and Faber (24). The ethidium bromide stained gel prior to the blotting is indicated below. 28s and 18s; ribosomal RNAs.
	FIG. 5. Whole mount in situ hybridization showing the localization of Xhlp (A, B) and Xron (C, D, E, F) mRNA in an embryo during neurula and tailbud stages. The stage 14 early neurula embryo hybridized with a Xhlp antisense RNA probe at anterior view (A) and dorsal view (B). Anterior view of the stage 14 early neurula embryo hybridized with a Xron antisense RNA probe (C) and a Xron sense RNA probe (D). Anterior view of the stage 18 late neurula embryo (E) and the stage 23 early tailbud embryo (F) hybridized with a Xron antisense RNA probe. Xhlp mRNA was detected in midline of the neural plate (notoplate) and the most frontal region of neural fold at stage 14 (A and B, arrowheads). Xron mRNA was detected in the most frontal region of the neural fold at stage 14 (C, arrowheads) and detected in the most anterior region of head structure and in eye placode at stages 18 and 23 (E and F, arrowheads).