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. 2015 Mar 6;19(6):1375–1389. doi: 10.1111/jcmm.12525

Figure 3.

Figure 3

ISL1 and TNNI2 expression at the venous pole at HH15-16. (A–D) 3D reconstructions, HH15 embryo. White: myocardium, blue: AV canal myocardium, green: ISL1+/TNNI2+ sinus venosus myocardium, purple: lumen (B). Left lateral view showing ISL1-/TNNI2+ myocardium (between arrowheads) between myocardium of AV canal and sinus venosus. (C and D) Right lateral view with (in C, part of ventricle and entire OFT are removed to expose right portion of inflow tract) and without (in D) myocardium reconstructed, demonstrating distance between sinus venosus and AV canal myocardium (between arrowheads). (E and F) Transverse section at HH15 of ISL1-/TNNI2+ myocardial connection between AV canal (identified based on morphological criteria, i.e. presence of thick endocardial cushions and underlying spongious myocardium) and lower region of atrium (between arrowheads). (G and H) ISL1+/TNNI2+ sinus venosus (including RCV myocardium), which is located caudally to connection between atrium and AV canal. (I and J) At HH16, RVV is a double leaflet with ISL1+/TNNI2+ myocardium in inner leaflet (arrowhead) and ISL1-/TNNI2+ myocardium in outer leaflet (arrow). (K and L) ISL1+/TNNI2+ continuity between the SV and AV canal (between arrowheads) is first seen at HH16. A: atrium; AVC: atrioventricular canal; EC: endocardial cushion; LCV: left cardinal vein; OFT: out-flow tract; RA: right atrium; RCV: right cardinal vein; SV: sinus venosus. White: TNNI2, green: ISL1, red: NKX2-5 blue: DAPI; scale bars: 50 μm.