Whole mount in situ hybridization of Notch1 pathway and somitogenic genes. Control (Notch1+/+) embryos (left) and mutant Notch1lbd/lbddenoted lbd/lbd (right) embryos were probed together. Arrows point to highest expression. (A) Notch1 expression in E8.75 control and Notch1lbd/lbdembryos was similar (~9.7 kb probe). (B) At E9.0 Notch1 expression was reduced in Notch1lbd/lbdcompared to control embryos (~4.7 kb probe). (C) At E9.5 Notch1 expression was barely detectable in Notch1lbd/lbdembryos (~9.7 kb probe). (D) Expression of the Notch target gene Hes5 was reduced in mutant embryos at E9.5, with residual expression in brain. (E) Myogenin was poorly and diffusely expressed in E9.5 Notch1lbd/lbdembryos. (F) Uncx4.1 was expressed in the caudal compartment of formed somites of control but was missing from the somitic region of E9.5 Notch1lbd/lbdembryos. Uncx4.1 was up-regulated in the midbrain (asterisk) of E9.5 Notch1lbd/lbdembryos (n ≥ 3 for mutant embryos for each probe).