FGFR2 (fibroblast growth factor receptor 2)

FGFR2 gene, consisting of at least 21 exons, encodes multiple isoforms due to alternative splicing. FGFR2b and FGFR2c with extracellular three Ig-like domains, transmembrane domain and cytoplasmic tyrosine kinase domain, are representative FGFR2 isoforms almost identical except the latter half of the third Ig-like domain. Exon 9 and 10, corresponding to the latter half of the third Ig-like domain, are incorporated into FGFR2b and FGFR2c in a mutually exclusive manner. Splicing silencer sequence within intron 8 and splicing activator sequence within intron 9 are implicated in the regulation of splicing preferentiality for FGFR2b and FGFR2c. Exons 20 and 21 of FGFR2 gene are alternative last exons encoding the C-terminal region of FGFR2 isoforms. Wild type FGFR2 transcripts with exon 21 are expressed in normal cells and most tumor cells, while aberrant FGFR2 transcripts with exon 20 are overexpressed in cases with FGFR2 gene amplification due to the exclusion of exon 21 from the FGFR2 amplicon. FGFR2 gene also encodes transmembrane-type FGFR2 isoforms lacking the first Ig-like domain, and secreted-type FGFR2 isoforms.