Asymmetric gene expression in Fgf4 knockdown embryos. The expression of southpaw in embryos at 20 hpf was examined by whole mount in situ hybridization. The expression was expanded anterior-laterally in the left LPM in wild-type embryos (a). In contrast, the expression of southpaw in Fgf4 MO1-injected embryos at 20 hpf was randomized (normal (33.3%, n = 30); reverse (23.3%, n = 30); bilateral (43.3%, n = 30)) (b–d). In wild-type embryos, the expression of pitx2 was detected in the LPM at 20 hpf (e). In contrast, the expression of pitx2 was randomized (normal (36.7%, n = 30); reverse (23.3%, n = 30), bilateral (20%, n = 30); absence (20%, n = 30)) (f–i). Although the expression of lefty1 was detected in the posterior notochord of wild-type embryos at 14 hpf, it was not detected in Fgf4 MO1-injected embryos (81.2%, n = 32) (j, k). The expression of lefty2 and lefty1 in the left cardiac field was examined in embryos at 18 hpf and 20 hpf, respectively. The expression of lefty2 was strongly detected in the cardiac field of wild-type embryos (l, n). However, the expression was not detected in Fgf4 MO1-injected embryos (93.3%, n = 30) (m, o). The expression of lefty1 was weakly detected in the cardiac field of wild-type embryos (p). The expression was not detected in Fgf4 MO1-injected embryos (86.7%, n = 30) (q). Arrows indicate positive staining. Scale bars = 200 μm.
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