Genetic techniques have been used to delete different combinations of fibroblast growth factors (FGFs) from the mouse limb, to study the contribution that each FGF makes to the total apical ectodermal ridge (AER)–FGF signal. Out of the four AER–FGFs, it is shown that only one of them, Fgf8 is sufficient for normal limb development. This dispels a longstanding notion that there is a positive feedback loop between the three other FGF genes expressed in the posterior AER, and the sonic hedgehog gene.
- Francesca V. Mariani
- Christina P. Ahn
- Gail R. Martin
