Fig. 3

Myocardial morphogenesis establishes left-right laterality from two distinct antero-posterior fields.

Confocal projections of Tg(meis2b-reporter);Tg(myl7:mCherry) embryos between the 17 ss (16 hpf) and 50 hpf. (a-c) Myocardial progenitors migrate to the midline and form the cardiac disc, where Tg(meis2b-reporter) expression is confined to the posterior compartment of the cardiac disc (PDC). (d) Cardiomyocytes forming the cardiac disc appear to migrate clock-wise, rotating the forming heart tube. (e) Tg(meis2b-reporter)-expressing cells are located on the ventral side of the heart tube. (f) At 50 hpf, Tg(meis2b-reporter) expression appears on the left side of the atrium, and in a small part of the ventricle near the AV canal. (a’-f’) 3D rendered sections (as indicated in the third column, white dotted lines) of the hearts shown in a-f (see Figure 3—videos 1–6 for full reconstructions). (a’’-f’’) Schematic representation of Tg(meis2b-reporter);Tg(myl7:mCherry) expression from (a’-f’). White dotted lines delineate the heart, yellow dotted lines delineate Tg(meis2b-reporter) expression. White dotted lines in third column indicate the level of the sagittal and transverse views. First to third columns: ventral views, anterior up; (a’-e’, a’’-e’’) sagittal views, anterior up; (f’, f’’) transverse views, dorsal up. Scale bars: (a-e’) 100 µm, (f’) 50 µm.