Murine fibroblast growth factor receptor 1 gene generates multiple messenger RNAs containing two open reading frames via alternative splicing.

The arrangement of exons and introns encoding 5'-side of murine fibroblast growth factor (FGF) receptor 1 (FGFR-1) gene was mapped. A large intron with a size of 14 kb was identified between exon 1 and exon 2. In addition, all FGFR-1 subtypes including a unique variant form with 12 amino acids insertion and two amino acids deletion were observed to be able to be generated through alternative splicing. Furthermore, complete sequencing of the 5'-region of FGFR-1 mRNA revealed that a relatively large open reading frame precedes the major open reading frame encoding FGFR-1. These results indicate that FGFR-1 mRNAs are uniquely translated from an internal translation start site.