MOLECULAR-CLONING OF XENOPUS HGF CDNA AND ITS EXPRESSION STUDIES IN XENOPUS EARLY EMBRYOGENESIS

We isolated Xenopus HGF cDNA and examined its expression pattern in Xe nopus early embryos and their dissected parts. Xenopus HGF consists of 710 amino acids and contains four kringle domains and serine protease -like structure just like mammalian HGF. Northern blot analysis showed that expression of Xenopus HGF mRNA starts at the late gastrula stage and its level increases during the period of later embryogenesis. Dis section experiments revealed that Xenopus HGF mRNA is expressed in the mesoderm region, especially in the ventral mesoderm, which for the mo st part gives rise to mesenchymal cells. Furthermore, HGF mRNA was exp ressed in response to activin A and basic FGF in blastula animal cap c ells. Interestingly, a stronger activity was observed with bFGF than w ith activin and this finding corroborates the preferential expression of HGF mRNA in the ventral mesoderm. Based on these results, we conclu de that the Xenopus homologue of HGF gene is transcribed during early embryogenesis preferentially in ventral mesodermal tissues, probably i n response to the signals that induce ventral mesoderm.