Figure 3.

FGF signaling maintains xsema3A and xslit1 expression in the forebrain. A–F, Stage 33/34 embryos were exposed to a control DMSO (A, C, E) or 100 μm FGFR inhibitor (SU5402) (B, D, F) solution for 10 h and then processed for guidance cue expression by in situ hybridization. To best observe expression patterns, embryos were viewed from a lateral perspective for xsema3A (A, B) and xslit1 (C, D) and a dorsal perspective for xslit2 (E, F). Embryos were scored in a blinded manner for intensity of staining from 1 (indicating light staining) to 3 (indicating dark staining). G, Bar graph illustrates the average intensity scores for each riboprobe. Graphs indicate a significant decrease in xsema3A and xslit1 but not xslit2 expression after SU5402 treatment (Mann–Whitney rank sum test). H, Representative image of the change in xsema3A mRNA levels after exposure to SU5402 as assessed by RT-PCR. I, Stage 33/34 embryos were exposed to a control DMSO or 100 μm SU5402 solution for 2, 6, or 10 h and then processed for xsema3A expression by in situ hybridization and analyzed as in G. A significant decrease in xsema3A expression was observed after 6 and 10 h of exposure to the inhibitor (Dunn's post hoc method). A↔ P, Anterior/posterior axis; pi, pineal gland; tel, telencephalon. Scale bar, 100 μm. Graphs depict mean ± SEM. **p < 0.01.