Fig. 3
Membrane fusion occurs in the developing heart. Live imaging of Tg(myl7:MKATE-CAAX);Tg(myl7:H2B-GFP) embryos, in which heartbeats were blocked by morpholino-mediated tnnt2 knock-down (Supplementary Movie 1), showing establishment of a new membrane border (arrows) between cardiomyocytes 1 and 2, which initially exhibited cytoplasmic continuum. The plasma membrane border between cardiomyocytes 1 and 3 (arrowheads) dissolved and was subsequently re-established. mKATE-CAAX (red) and H2B-GFP (green) expression labeled cardiomyocyte membranes and nuclei, respectively. Timing of each still image is hour:minute. All images are 3D volume renderings of 60 μm thick confocal stacks of a representative heart showing the myocardial monolayer observed from the lumen. Examples of cytoplasmic continuum between cardiomyocytes were observed in all 6 hearts examined. Scale bar: 20 μm