(A-H) Immunofluorescence of active caspase 3 (Casp3, green), phospho-histone H3 (pH3, red), SSEA1 (green), and non-muscle myosin heavy chain IIA (NMHCIIA, red) in frontal sections of E14.5 control and K14-Cre;R26SmoM2 palatal shelves. Arrows indicate positive signal; arrowheads indicate absence of signal. White dotted lines indicate the location of the MEE. Scale bars: 50 μm.