<p>(A–D) Whole mount mRNA <i>in situ</i> hybridization to show Mecom expression. A–C) Expression during subsequent stages of heart tube formation E8.5 (black brackets). D) At E9.5 Evi1 is expressed in the endothelial cells and in the endocardium of the heart and in the mesenchyme of the aortic arches. Expression also includes a population of migrating neural crest cells (white arrowhead). E–J) E10.5 Sagittal sections (from right to left) showing Evi1 in the aortic arches (a), mesenchyme of the secondary heart field (black arrowheads), outflow and atrio-ventricular canal endocardium including the cushions.</p
