Fig. 3. Hand2 expression in Ednra^–/– and Dlx5/6^–/– embryos. (A-H) Ednra^+/+;R26R;Hand2-Cre and Ednra^–/–;R26R;Hand2-Cre embryos stained in whole mount for ß-gal activity and shown in both lateral (A,B) and ventral views (C,D). For ventral views, the heart and outflow tract have been removed. Embryos (not necessarily those shown in A-D) were then sectioned along either sagittal (E,F) or frontal (G,H) planes and counterstained with nuclear Fast Red. (A,C) In E10.5 Ednra^+/+;R26R;Hand2-Cre embryos, ß-gal-labeled cells are observed throughout pharyngeal arches 1 and 2. (B,D) In Ednra^–/–;R26R;Hand2-Cre embryos, labeled cells are observed only along the distocaudal aspect of mandibular arch. (E,G) In sagittal sections through the arches of Ednra^–/–;R26R;Hand2-Cre embryos, labeled cells are confined to the neural crest-derived mesenchyme. (F,H) In sagittal sections through the arches of Ednra^–/–;R26R;Hand2-Cre embryos, scattered labeled cells are observed in the distal mesenchyme, with more intense labeling observed in cells in the surrounding arch epithelium. (I-L) Analysis of Hand2 expression in Dlx5/Dlx6^–/– embryos. Normal Hand2 expression (I,K) is absent in the pharyngeal arches of Dlx5/Dlx6^–/– embryos (J,L), although residual expression is still observed in the distal mandibular arch (yellow arrow in inset). A small expression domain is present in the second arch (black arrows in L).