Fig. 4. Ate1 knockout results in defects in myofibril continuity at intercataled disks. (A) Illustration of the structural parameters measured. (B) Frequency distribution of average myofibril angle at each intercalated disk (above) and deviation of this angle from 90° (below). (C) Cell-cell distance averaged for all wild-type mouse hearts together (light-gray bars) and for individual knockout hearts (dark-gray bars), sorted by embryo age. As the severity of the knockout phenotype progresses, the average cell-cell distance, as well as the standard deviation between distances in a single heart, increase, as seen at E14 for the three KO hearts shown. (D,E) Examples of intercalated disks in the wild type (D) and knockout (E). Abnormalities at intercalated disks included disorganization of the myofibrils resulting in angle deviations from 90° for incoming filaments (E, top two images), myofibril asymmetry on the two sides of the intercalated disk (E, the middle two images), and disruption of the cell-cell contacts at intercalated disks (E, bottom). Scale bars: 500 nm in D; 500 nm in E, except for bottom image at 2 µm.