Fig. 1.

Genetic fate mapping and apoptosis of Pax3^Cre;Wls-cKO midfacial primordia. (A-L) EGFP expression, representing Pax3^Cre recombination patterns in the midfacial primordia of E11-E12.5 Wls-het (A,C,E,G,I,K) and Wls-cKO (B,D,F,H,J,L) embryos. Dashed lines in A,B indicate respective section regions shown in C-F. Arrows indicate the facial midline between the paired MNPs during or after merging. Dashed arrows and arrowheads in C,D indicate EGFP-positive nasal epithelial cells and adjacent surface ectodermal cells around the dorsal nasal tips. Arrowheads in E,F indicate EGFP-negative surface ectodermal cells. Double-headed arrows in H,J show an enlarged midline gap in Wls-cKO embryos. Asterisks indicate the bilateral junction zone. (M-P) Whole-mount TUNEL assays for normal controls and Pax3^Cre;Wls-cKOs at E10.5 and E11.0-E11.25. Arrows indicate apoptotic cells in the forehead region adjacent to the dorsal nasal prominences. Arrowheads indicate apoptotic cells in the dorsal junction zone between the LNP and LMP. Asterisks in O,P indicate apoptotic cells at the junction zone during bilateral upper lip fusion. fb, forebrain neuroepithelia; lnp, lateral nasal prominence; man, mandibular prominence; mnp, medial nasal prominence; mxp, maxillary prominence; n, nasal pit; oe, olfactory epithelia.