Cloning and characterization of a cDNA encoding er1, a novel developmentally regulated FGF response gene

In order to investigate the molecular mechanism of mesoderm induction by FGF in Xenopus Laevis, I have utilized the polymerase chain reaction (PCR)-based differential display methodology (Liang and Pardee, 1992) to identity a novel transcript whose expression level increased in Xenopus embryo explants during mesoderm induction by fibroblast growth factor (FGF). The PCR product was used to clone a 2.3-kb cDNA representing this transcript, which I have named er1. The er1 cDNA contains a single open reading frame (ORF) predicted to encode a protein of 493 amino acid residues. Northern blot analysis revealed a single 2.8-kb mRNA that was observed predominantly during the initial cleavage and blastula stages of Xenopus development, with little or no detected mRNA during subsequent development. In vitro translation of er1 using a rabbit reticulocyte lysate system produced a protein with an apparent molecular mass of 74kDa. A database homology search revealed that the predicted er1 amino acid sequence contains three regions of similarity to the rat metastasis-associated gene mta1. FGF is known to play an important role in both mesoderm induction and gastrulation movement during amphibian development, elucidation of the function of this mta1-related FGF response gene may lead to a better understanding of the early development of Xenopus Laevis