Fig. 5. Notch1 signaling is altered in Lfng^FCE1/FCE1 embryos. Whole-mount immunohistochemistry using an antibody specific for activated Notch1 was performed. (A) At 8.5 dpc, dynamic domains of Notch activation are seen in wild-type embryos, with anterior bands and a posterior band of varying width (a,b, n=29). In both Lfng^FCE1/FCE1 (c, n=12) and Lfng^-/- (d, n=7) embryos, Notch1 activation is seen ubiquitously throughout the PSM. (B) At 10.5 dpc, dynamic Notch1 activation is observed in wild-type embryos, with four distinct phases observed [a-d n=9/38 Phase 1, 8/38 Phase 2, 11/38 Phase 3 and 10/38 Phase 4, as defined in Morimoto et al. (Morimoto et al., 2005)]. By contrast, Lfng^FCE1/FCE1 (e, n=17) and Lfng^-/- (f, n=8) embryos exhibit a gradient of Notch1 activation throughout the PSM. Yellow bars indicate the extent of the stained regions.