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

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.