gata4, gata5 and gata6 are essential for anterior haemangioblast specification. (A) gata4, gata5 and gata6 are expressed in overlapping yet distinct domains throughout the anterior lateral plate mesoderm (ALM). (B) Expression of l-plastin, mpx and ikaros, genes associated with myelopoiesis, was absent in gata5+gata6 morphants at 24 hpf. (C) Analysis of earlier regulatory myeloid gene expression on knock down of gata5 and gata6 shows ablation of cmyb, ikaros and pu1 at 10 somites (red arrowheads). (B,C) The number of embryos exhibiting this phenotype shown at the bottom right-hand corner of each panel. (D) Expression of haemangioblast-associated genes close to the onset of their expression was downregulated in gata5+gata6 morphants (marked by red arrowheads where necessary). uncx4.1 was used as a somite marker to stage the embryos (white brackets). n=40-100 for each gene analysed, the pictures shown depict >95% of the embryos. Views are: (A) flatmounted, anterior to the top; (B) lateral, anterior to left, except for ikaros, which is an anterior view; (C) dorsal, anterior to the top; (D) anterior-dorsal.