E9.5 FVB/N KLF2−/− atrioventricular cushions have accumulated cells lining the AV canal.

(A) and (C) are WT (n = 4) and (B) and (D) are KLF2−/− (n = 4) hearts. Micrographs A and B (magnification 50X) show atrial (At) and ventricular (V) chambers. The boxes or brackets enclose the endocardial cushions (EC) shown at higher magnification in C and D (400X). Endo: Endocardial cells; Myo: Myocardium; Ery: erythroid cells; Mes: Mesenchymal cells. (E) Bar chart representing the number of cells/mm2 lining the AV canal of E9.5 WT and KLF2−/− embryos. The Student’s t-test indicates that the number of cells is significantly greater in KLF2−/− than in WT (p = 0.0078). n = 4.