Effect of GSI and fragments of Gleevec on Notch target gene her6 expression. Embryos were treated with the compounds at 24 hpf and fixed at 48 hpf in 4% formaldehyde. In situ hybridization was performed to stain her6 staining. In control embryos, her6 expression was abundant in the dorsal diencephalon, retinas, ventral midbrain and ventral hindbrain, and it was lower in telencephalon, olfactory vesicles, branchial arches, ventral hindbrain and pectoral fins A, these regions are indicated by arrows; A', the her6-positive brain regions from the dorsal view images were manually segmented; A", the same embryo was illustrated for the comparison of staining intensity. B-G, her6 expression in embryos treated with different concentrations of DAPT, Gleevec, or fragments of Gleevec.