An important role for the IIIb isoform of fibroblast growth factor receptor 2 (FGFR2) in mesenchymal-epithelial signalling during mouse organogenesis

The fibroblast growth factor receptor 2 gene is differentially spliced to e ncode two transmembrane tyrosine kinase receptor proteins that have differe nt ligand-binding specificities and exclusive tissue distributions. We have used Cre-mediated excision to generate mice lacking the IIIb form of fibro blast growth factor receptor 2 whilst retaining expression of the me form, Fibroblast growth factor receptor 2(IIIb) null mice are viable until birth, but have severe defects of the limbs, lung and anterior pituitary gland. T he development of these structures appears to initiate, but then fails with the tissues undergoing extensive apoptosis. There are also developmental a bnormalities of the salivary glands, inner ear, teeth and skin, as well as minor defects in skull formation, Our findings point to a key role for fibr oblast growth factor receptor 2(IIIb) in mesenchymal-epithelial signalling during early organogenesis.