Fig. 5

Atp1a1 is required in the yolk syncytial layer for heart tube elongation. (A) Embryos injected at the 512 to 1000-cell stage with fluorescein-tagged atp1a1MO1 exhibit a yolk-specific fluorescence pattern at 24 hpf, indicating that the morpholino′s effects are restricted to the yolk syncytial layer. (B,C) Microtome sections of atp1a1 expression in 12S stage wild type and atp1a1MO1^YSL embryos. Strong expression of atp1a1 is visible in the YSL of wild type embryos (arrowheads, B), whereas atp1a1MO1^YSL embryos display a specific loss of YSL expression of atp1a1 while maintaining normal embryonic expression (C). (D–G) Dorsal views of cmlc2 expression in 24 hpf uninjected and YSL-morphant embryos. Uninjected and standard control oligo YSL-injected (std ctrl MO^YSL) embryos have an elongated heart tube at 24 hpf visualized by cmlc2 expression (D,F) whereas most atp1a1MO1^YSL and atp1a1MO2^YSL embryos have a clump of cardiomyocytes at the midline at 24 hpf (E,G). (H,I) Dorsal views of fn1 expression in the cardiac region of 15S stage wild type and YSL-morphant embryos. Expression of fn1 is reduced in atp1a1MO1^YSL embryos (I) compared to wild type embryos (H).