FIG. 6.

Calcrl^−/− and AM^−/− embryos have defects in cardiac cell proliferation. The proliferation index of cardiac cells was determined as the number of BrdU-positive cells per total area in transverse heart sections. (a) No significant difference was found between wild-type and Calcrl^−/− embryos at E11.5. However, at E12.5 the proliferation index was significantly lower in Calcrl^−/− embryos than in wild-type controls. (b) The proliferation index of AM^−/− embryos at E13.5 is significantly lower than that of wild-type littermates.