|
Figure 1. Cardiac genes expression at stages 39, 40, 41, and 45 by whole-mount in situ hybridization. In all panels, a lateral view of the cardiac region is shown, anterior to right, dorsal to top. Blue and red arrows indicate the position of the OFT and AV valves, respectively. Scale bar = 100 mu m.
|
|
Figure 3. Cardiac gene expression at stage 39 by in situ hybridization on section. Transverse and sagittal sections are at the level of the OFT and AV canal, respectively. A, G: Hematoxylin/eosin (H-E) stained sections. Bmp4 (B, H), Msx1 (C, I), and Nkx2.5 (D, J) are expressed in the myocardium while Sox9 (E, K) and Xl-Fli (F, L) are detected in the endocardium. CJ, cardiac jelly; E, endocardium; EMT, site of epithelial-to-mesenchymal transformation; L, liver; M, myocardium. Scale bar = 50 mu m.
|
|
Figure 4. Cardiac gene expression at stage 41 by in situ hybridization on section. Transverse and sagittal sections are at the level of the OFT and AV canal, respectively. A, J: Hematoxylin/eosin (H-E) stained sections. Bmp4 (B, K), Msx1 (C, L), and Nkx2.5 (D, M) are expressed in the myocardium. Frzb1 (E, N), Sox8 (F, O), Sox9 (G, P), and Xl-Fli (I, R) are expressed in the mesenchyme of the OFT and AV cushions. Sox10 (H, Q) is weakly expressed in the OFT mesenchyme. AV, atrioventricular cushion; L, liver; OFT, outflow tract cushion; V, ventricle. Scale bar = 50 mu m.
|
|
Figure 5. Cardiac genes expression at stage 45 by in situ hybridization on section. Transverse and sagittal sections are at the level of the OFT and AV canal, respectively. A,J: Hematoxylin/eosin (H-E) stained sections. Bmp4 (B, K), Msx1 (C, L), and Nkx2.5 (D, M) are expressed in the myocardium. Frzb1 (E, N), Sox8 (F, O), Sox9 (G, P), and Xl-Fli (I, R) are differentially expressed in the mesenchyme of the OFT and AV cushions. Sox10 (H, Q) is detected in the middle portion of the OFT cushion. A, atrium; AV, atrioventricular valve; OFT, outflow tract valve; V, ventricle. Scale bar = 50 mu m.
|
|
Figure 2. Diagram illustrating the orientation of the transverse and sagittal sections in subsequent figures. Lateral view (A) and ventral view (B) of a stage-39 embryo. The black lines indicate the level of the transverse (A) and sagittal (B) sections. The diagrams are modified from Nieuwkoop and Faber (1967). C, D: Higher magnification of the two regions boxed in A and B. The position of the developing OFT and AV canal is indicated in blue and red, respectively. E, F: Schematic representation of the H-E stained sections as shown in Figure 3A and G, respectively, illustrating the topography of the tissues as they relate to cardiac cushion formation. The positions of future OFT (blue) and AV (red) cushions are highlighted. AA, aortic artery; AVC, atrioventricular canal; CJ, cardiac jelly; E, endocardium; EMT, site of epithelial-to-mesenchymal transformation; G, gut; L, liver; M, myocardium; OFT, outflow tract; PE, pharyngeal endoderm; PM, pharyngeal mesoderm; V, ventricle.
|
|
Figure 6. Summary of the timeline of cardiac genes expression in Xenopus as they relate to cardiac cushions formation. The letters indicate key stages of heart development based on this study and previously published work (Nieuwkoop and Faber, 1967; Kolker et al., 2000; Mohun et al., 2000; Lohr and Yost, 2000). A: Initiation of epithelial-to-mesenchymal transformation of the endocardium lining the AV cushion. B: Initiation of epithelial-to-mesenchymal transformation of the endocardium lining the OFT cushion. C: OFT spiral septum and AV valves are formed. D: Atrial septation is completed.
|
