Expression of nkx2.5 and GATA4 in zebrafish morphants of GATA4, 5 and/or 6 separately and in combination. Flat mounts, dorsal views (A) A, anterior; P, posterior; D, dorsal; V, ventral. (B) As seen at 26 hpf (Fig. 4), GATA4 morphants at 10 somites showed normal expression of nkx2.5, whereas GATA6, and more severely GATA5, morphants showed a reduction in expression. In combination morpholino injections, down regulation was exacerbated in each case, as seen at 26 hpf (Fig. 4), with expression being completely absent in embryos depleted for both GATA5 + 6. (C) Loss of GATA5 reduces the expression of GATA4 and there is a complete loss of GATA4 expression when GATA5 and 6 are depleted in combination (G5 + G6MO). The black brackets indicate the cardiac expression. Krox20 and MyoD are stained in red and were used as landmarks. Krox20 is expressed in rhombomeres 3 and 5, MyoD was used to confirm the number of somites in the embryo.