smarcc1a is required to restrict patterns of gene expression to the AVC. Whole-mount in situ hybridization compares expression patterns of bmp4 (A–F), vcana (G–L), and notch1b (M–R) expression between 30 and 48 hpf. (A, D, G, J) Dorsal views, ventricle to the top. (B, C, E, F, H, I, K, L, N, O, Q, R) Frontal views, ventricle to the top. (M, P) Lateral views, anterior to the left; arrows indicate the ventricular end of the heart tube. (A, D, G, J, M, P) The initial broad expression of all three genes is similar in wild-type and smarcc1a mutant embryos. (B, E) In smarcc1a mutants at 38 hpf, the expression of bmp4 continues to resemble wild-type expression, with higher levels in the ventricle and inflow tract and lower levels in the atrium. (H, K) Expression of vcana is perturbed in smarcc1a mutants at 38 hpf, with high levels found throughout the heart. (N, Q) The expression of notch1b in smarcc1a mutants at 38 hpf is higher in the ventricular endocardium than in the atrial endocardium, similar to the pattern seen in wild-type. (C, F, I, L, O, R) In wild-type at 48 hpf, the refined patterns of bmp4, vcana, and notch1b feature concentrated expression in the AVC (arrowheads in C, I, O), and this refinement does not occur in smarcc1a mutants.
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