Four classes of mRNA are expressed from the mouse int-2 gene, a member of the FGF gene family.

Mouse embryos at 7.5 days of gestation and endodermal cells derived from embryonal carcinoma cells each express four int-2 mRNAs of similar size and relative abundance. To determine their structure and coding potential, we prepared a cDNA library from endoderm mRNA and isolated several int-2 cDNAs. Structural analysis of these cDNAs combined with Northern blot hybridization and primer extension analyses of int-2 mRNA revealed that the differences between the mRNAs are generated through the use of two alternate transcriptional start sites and two alternate polyadenylation sites. All four mRNAs share a common core sequence that encodes a protein with amino acid similarity to fibroblast growth factor.