Fig. 2. Ate1 knockout results in the delayed development and the disorganization of cardiac myofibrils. Electron microscopy images of sections of wild-type (WT, left column) and knockout (KO, right column) E14.5 mouse hearts at 2500x magnification. The same images are shown in the bottom row, but with myofibrils highlighted in green. In the wild type at E14.5, myofibrils are prominent and are oriented along the axis of the heart muscle. In the knockout at the same stage, myofibrils are much less abundant and difficult to trace over continuous distances, suggesting a defect in overall myofibril organization and cardiac contractility. Scale bars: 10 µm.