Fig. 6. Expression of neuronal markers is altered in embryos lacking Fgf8 and Fgf3. Lateral views of whole-mounted embryos with anterior to the left. (A-D) zash1a expression at 18 hpf. In control embryos, zash1a expression is detected in the dorsorostral cluster in the telencephalon and in the ventrorostral cluster in the diencephalon, as well as in the presumptive epiphysis (A). Injection of Fgf8mo results in a slight reduction of zash1a expression in neurons of the ventral diencephalon. By contrast, expression within the presumptive epiphysis is expanded (B). zash1a expression is lost from dorsorostral and ventrorostral clusters, but is expanded in the presumptive epiphysis in embryos injected with either Fgf3mo alone (C), or with Fgf8mo and Fgf3mo (D). (E-H) isl1 expression at 30 hpf. In control embryos, isl1 is expressed in a subset of neurons within dorsorostral and ventrorostral clusters (E). There is very little effect on isl1 expression following fgf8mo injection (F). isl1 expression is reduced in the dorsorostral and ventrorostral clusters in embryos injected with Fgf3mo (G), and reduced in the dorsorostral cluster and virtually absent in the ventrorostral cluster in embryos injected with both Fgf8mo and Fgf3mo (H). (I-L) lim1 expression at 30 hpf. lim1 is expressed in a subset of neurons within the dorsorostral and ventrorostral clusters (I), and is unaffected following Fgf8mo injection (J). Injection of Fgf3mo results in reduced lim1 expression in many neuronal populations of the brain, including dorsorostral and ventrorostral clusters (K), whereas lim1 expression is lacking in most neuronal populations, including the dorsorostral and ventrorostral clusters, following injection with both Fgf8mo and Fgf3mo (L). d, diencephalon; drc, dorsorostral cluster; ep, presumptive epiphysis; tel, telencephalon; vrc, ventrorostral cluster.