<i>Sox2-Cre</i>-mediated conditional knockout revealed that embryonic p600 is essential for heart development.

<p>(A) Impaired interventricular septum formation in <i>p600</i> cKO heart. From H&E stained transverse cross-sections of E12.5 embryos, the interventricular septum areas are shown. In the <i>p600</i>^+/− (<i>p600</i>^+/−/<i>Sox2-Cre</i>⁺) heart (left), the interventricular septum (IVS) is fused with inferior atrioventricular endocardial cushions (IC), separating the left and right ventricles. On the other hand, <i>p600</i> cKO heart has developmental defects of the interventricular septum. Scale bars indicate 500 µm. (B) The <i>p600</i>^+/− (left) and <i>p600</i> cKO (right) heart at E13.5. Scale bars indicate 200 µm. (C) Magnified images of ventricular wall. Magnified areas are indicated as boxes in (B). Scale bars indicate 100 µm. (D) Relative cell numbers of the ventricular wall in the <i>p600</i> cKO and <i>p600</i>^+/− hearts at E13.5. Cell numbers of ventricular wall areas were estimated from the several serial sections and shown as relative values. The statistical significance of the difference was calculated with Student’s t-test. * shows <i>p</i>-value <0.05.