Figure 3. P2Ztg expression throughout embryonic development and adulthood. Whole-mount embryonic views (A, A', B, F, L, O, P, R, and T) and transverse (C–E, G–K, Y) or longitudinal sections (M, N, O', Q, S, U–X) through the heart are shown. A–E:P2Ztg is expressed in anterior to posterior left LPM (A, black arrowheads, and B), including the cardiac crescent region (red dotted lines). Note that in right-sided view X-Gal staining on the left side can be seen due to embryo transparency (A'). At the linear heart stage, expression is retained in LPM (black dotted box in C), DM, and dorsal myocardial wall at different compartment levels (C–E). F–I: Cardiac expression encompasses IC (F and red star in G), ventral parts of cardiac chambers (F, yellow star in G), and LA/SV (G, I). Red arrowhead in D, I shows pharyngeal mesenchyme staining. J: Bilateral staining in BA. K:P2Ztg expression in posterior mesoderm. L: Dissection of atrial appendages reveals ventral P2Ztg expression on OFT (black arrowheads) and extensive LV staining. M,N: Sections show staining in interatrial septum (encircled in M) and discontinuous staining in pericardium (N, black arrowheads). O,O': Left sagittal view (O) and transverse section (O') showing X-Gal staining in blue and Nppa mRNA in purple. Red arrowheads point to double stained trabeculae. P, Q: Sharp horizontal stained boundary on ventral RV surface (red arrowheads) reflects septal staining. Q: X-Gal strongly marks compact (black arrowheads) and trabeculated (black stars) ventricular regions. R, S: P2Ztg stains AO exclusively (R), but disappears upon great vessels remodelling (T). U–Y: P2Ztg is not present in forming AVC (black stars in U) or OFT valves (dotted encircled regions in V, W). While atrial septal staining fades (U, black circle), atrial appendage (X) and ventricular (Y) stainings persist to adulthood. Red brackets in Y show blue cells along the total depth of ventricular walls; black arrowheads mark right-sided IVS staining. R, right; L, left; AL, allantois; HG, hindgut, DA, dorsal aorta; NP, neural plate; AM, amnion; HF, head folds; DM, dorsal mesocardium; OFT, outflow tract; YS, yolk sac; V, primitive ventricle; FG, foregut pocket; RA/LA, right/left atrium; AVC, atrioventricular canal; RV/LV, right/left ventricle; SV, sinus venosa; BW, body wall; MC, midgut cavity; PC, peritoneal cavity; MW, midgut wall; AO, aorta; PA, pulmonary artery; IVS, interventricular septum.
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