Comparison of the expression of three highly related genes, Fgf8, Fgf17 and Fgf18, in the mouse embryo.

In mammals, 16 members of the Fgf family have so far been described with diverse roles in embryonic cell growth and differentiation. Here, we report the expression from early streak stage to midgestation of two newly-identified murine genes, Fgf17 and Fgf18, that are most closely related to Fgf8 (63.7% and 56.8% identical, respectively, at the amino acid level). Fgf17 is expressed during gastrulation but at lower levels than Fgf8, while Fgf18 RNA is not expressed until later, in paraxial mesoderm. In the developing tail bud, each Fgf gene shows a different pattern of transcription. Distinct and overlapping expression patterns are also described in the developing brain and limbs.