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Fig. 5. Fate of Hand2 daughter cells in Ednra–/–;R26R;Hand2-Cre embryos. E16.5 Ednra+/+;R26R;Hand2-Cre (A,C,E,G,I) and Ednra–/–;R26R;Hand2-Cre (B,D,F,H,J) embryos stained for ß-gal activity in whole-mount (A-F) or sections (G,H), or analyzed for Hand2 expression using sectional in situ hybridization (I,J). (A,B) In a lateral view, ß-gal-labeled cells are observed throughout the lower jaw of Ednra+/+;R26R;Hand2-Cre embryos (A). In Ednra–/–;R26R;Hand2-Cre embryos, staining is confined to ventral surface of the mandible (B). (C,D) In a ventral view, few labeled cells are present in the lower jaw in Ednra–/– embryos (D), although the labeling is very prominent in the cleft between the two mandibular halves (arrow in D). (E,F) After clearing in benzyl benzoate:benzyl alcohol, little structural detail is apparent in the lower jaw of wild-type embryos because of the extensive labeling (E). By contrast, labeled cells in Ednra–/– embryos are present in the epithelial seam between the two arch halves (arrow in F), hypoplastic tongue (t) and lower incisors (i). (G, H) Stained sagittal cryosections illustrate labeling in most lower jaw structures and surrounding soft tissue of wild-type embryos, including the mandible (md), Meckel's cartilage (mc) and dental pulp of the incisors (arrow in inset) (G). Labeling is not observed in the dental lamina (dl; * in inset). In Ednra–/– embryos, labeled cells are present in the dental pulp of the lower incisors (arrow in inset), but are more scattered compared with wild-type embryos. A few labeled cells are also present in the small residual bone and cartilage underneath the incisors and in the dental lamina (* in inset) (H). Rugae are obvious along the both the top and bottom of the oral cavity (arrows). (I,J) Hand2 expression is observed in the dental pulp of both wild-type and mutant embryos, with highest expression in the odontoblast layer (yellow arrow in insets). Expression is not observed in either embryo within the dental lamina (black arrow in insets). p, secondary palate tissue.