Fate mapping studies in the OVE1070 cranium. X-Gal staining of E17 embryos. Panels A-D are top views and panels A'-D' are lateral views of intact heads. In the absence of Wnt1-Cre, lacZ positive cells were not detected in the R26R embryo (A, A') or the FGF9/R26R embryo (B, B'). In the Wnt1-Cre/R26R embryo (C, C'), the parietal region (p) of the skull shows no evidence for lacZ activity, implying that neural crest cells do not contribute to this region of the skull. In the FGF9/Wnt1-Cre/R26R embryo (D, D'), there is also no blue staining in the (enlarged) parietal region. In order to distinguish the staining in the skull (E) from the staining in the underlying brain (F, asterisk), the calvarium was removed intact from embryo D and the two parts of the head are shown as top views (E, F). Since the dorsal retinal pigmented epithelium in the FGF9 transgenic mice transdifferentiates into the neural retina , pigmentation is seen only in the ventral half of the eye (B', arrow). Abbreviations: f, frontal; ip, interparietal.