Fig. 3

Reduction of cardiac jelly thickness in developing zebrafish.

(a–h) Mid-sagittal confocal sections of late embryonic and early larval zebrafish hearts. Animals from Tg(kdrl:Hsa.HRAS-mCherry);Tg(myl7:EGFP-Hsa.HRAS) incrosses were synchronized at the tail bud stage (10 hpf) and imaged at 48 (a), 54 (b), 60 (c), 72 (d), 80 (e), 96 (f), 120 (g) and 144 hpf (h); endocardial and myocardial membranes are labelled in red and green, respectively; AV, atrioventricular canal, At, atrium; V, ventricle; scale bars, 50 μm. Higher magnification images of outer curvature area of ventricular (white dashed boxes) and atrial (yellow dashed boxes) walls are shown beneath each time point, respectively. The cardiac jelly is initially thicker in the atrium than in the ventricle at 48 hpf (a). It is greatly reduced in the ventricle by 72 hpf, (b–d) and almost fully gone by 96 hpf, while it is still detectable at 120 hpf in the atrium (e–h); arrowheads point to trabecular cardiomyocytes; arrows and asterisks indicate the presence and absence of cardiac jelly, respectively.