Neural induction and patterning in embryos deficient in FGF signaling.

We have examined the role of FGFs in neural induction and posteriorization of the central nervous system (CNS). Using embryos micro-injected with dominant negative FGF receptor RNA (XFD), we show that a patterned CNS can still develop following inhibition of FGF signaling. The most severely affected embryos developed with strong posterior defects. In these embryos, head development and expression of a marker of forebrain and midbrain, and of markers of the hindbrain, occurred relatively normally. However, the expression levels of a posterior marker, Hoxb-9, were considerably reduced compared to those in control embryos. The results support the idea that FGFs are involved in inducing posterior development, but they suggest that other signals are also necessary for antero-posterior patterning of the primary body axis.